Sometimes immediately hard offlining a large chunk of contigous memory
having uncorrected memory errors (UE) may not be the best option.
Cloud providers usually serve capacity- and performance-critical guest
memory with 1G HugeTLB hugepages, as this significantly reduces the
overhead associated with managing page tables and TLB misses. However,
for today's HugeTLB system, once a byte of memory in a hugepage is
hardware corrupted, the kernel discards the whole hugepage, including
the healthy portion. Customer workload running in the VM can hardly
recover from such a great loss of memory.
Therefore keeping or discarding a large chunk of contiguous memory
owned by userspace (particularly to serve guest memory) due to
recoverable UE may better be controlled by userspace process
that owns the memory, e.g. VMM in Cloud environment.
Introduce a memfd-based userspace memory failure (MFR) policy,
MFD_MF_KEEP_UE_MAPPED. It is intended to be supported for other memfd,
but the current implementation only covers HugeTLB.
For any hugepage associated with the MFD_MF_KEEP_UE_MAPPED enabled memfd,
whenever it runs into a UE, MFR doesn't hard offline the HWPoison-ed
huge folio. IOW the HWPoison-ed memory remains accessible via the memory
mapping created with that memfd. MFR still sends SIGBUS to the process
as required. MFR also still maintains HWPoison metadata for the hugepage
having the UE.
A HWPoison-ed hugepage will be immediately isolated and prevented from
future allocation once userspace truncates it via the memfd, or the
owning memfd is closed.
By default MFD_MF_KEEP_UE_MAPPED is not set, and MFR hard offlines
hugepages having UEs.
Tested with selftest in the follow-up commit.
Signed-off-by: Jiaqi Yan <jiaqiyan@google.com>
Tested-by: William Roche <william.roche@oracle.com>
---
fs/hugetlbfs/inode.c | 25 +++++++-
include/linux/hugetlb.h | 7 +++
include/linux/pagemap.h | 24 +++++++
include/uapi/linux/memfd.h | 6 ++
mm/hugetlb.c | 20 +++++-
mm/memfd.c | 15 ++++-
mm/memory-failure.c | 124 +++++++++++++++++++++++++++++++++----
7 files changed, 202 insertions(+), 19 deletions(-)
diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index f42548ee9083c..f8a5aa091d51d 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -532,6 +532,18 @@ static bool remove_inode_single_folio(struct hstate *h, struct inode *inode,
}
folio_unlock(folio);
+
+ /*
+ * There may be pending HWPoison-ed folios when a memfd is being
+ * removed or part of it is being truncated.
+ *
+ * HugeTLBFS' error_remove_folio keeps the HWPoison-ed folios in
+ * page cache until mm wants to drop the folio at the end of the
+ * of the filemap. At this point, if memory failure was delayed
+ * by MFD_MF_KEEP_UE_MAPPED in the past, we can now deal with it.
+ */
+ filemap_offline_hwpoison_folio(mapping, folio);
+
return ret;
}
@@ -563,13 +575,13 @@ static void remove_inode_hugepages(struct inode *inode, loff_t lstart,
const pgoff_t end = lend >> PAGE_SHIFT;
struct folio_batch fbatch;
pgoff_t next, index;
- int i, freed = 0;
+ int i, j, freed = 0;
bool truncate_op = (lend == LLONG_MAX);
folio_batch_init(&fbatch);
next = lstart >> PAGE_SHIFT;
while (filemap_get_folios(mapping, &next, end - 1, &fbatch)) {
- for (i = 0; i < folio_batch_count(&fbatch); ++i) {
+ for (i = 0, j = 0; i < folio_batch_count(&fbatch); ++i) {
struct folio *folio = fbatch.folios[i];
u32 hash = 0;
@@ -584,8 +596,17 @@ static void remove_inode_hugepages(struct inode *inode, loff_t lstart,
index, truncate_op))
freed++;
+ /*
+ * Skip HWPoison-ed hugepages, which should no
+ * longer be hugetlb if successfully dissolved.
+ */
+ if (folio_test_hugetlb(folio))
+ fbatch.folios[j++] = folio;
+
mutex_unlock(&hugetlb_fault_mutex_table[hash]);
}
+ fbatch.nr = j;
+
folio_batch_release(&fbatch);
cond_resched();
}
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 8e63e46b8e1f0..b7733ef5ee917 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -871,10 +871,17 @@ int dissolve_free_hugetlb_folios(unsigned long start_pfn,
#ifdef CONFIG_MEMORY_FAILURE
extern void folio_clear_hugetlb_hwpoison(struct folio *folio);
+extern bool hugetlb_should_keep_hwpoison_mapped(struct folio *folio,
+ struct address_space *mapping);
#else
static inline void folio_clear_hugetlb_hwpoison(struct folio *folio)
{
}
+static inline bool hugetlb_should_keep_hwpoison_mapped(struct folio *folio
+ struct address_space *mapping)
+{
+ return false;
+}
#endif
#ifdef CONFIG_ARCH_ENABLE_HUGEPAGE_MIGRATION
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 09b581c1d878d..9ad511aacde7c 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -213,6 +213,8 @@ enum mapping_flags {
AS_WRITEBACK_MAY_DEADLOCK_ON_RECLAIM = 9,
AS_KERNEL_FILE = 10, /* mapping for a fake kernel file that shouldn't
account usage to user cgroups */
+ /* For MFD_MF_KEEP_UE_MAPPED. */
+ AS_MF_KEEP_UE_MAPPED = 11,
/* Bits 16-25 are used for FOLIO_ORDER */
AS_FOLIO_ORDER_BITS = 5,
AS_FOLIO_ORDER_MIN = 16,
@@ -348,6 +350,16 @@ static inline bool mapping_writeback_may_deadlock_on_reclaim(const struct addres
return test_bit(AS_WRITEBACK_MAY_DEADLOCK_ON_RECLAIM, &mapping->flags);
}
+static inline bool mapping_mf_keep_ue_mapped(const struct address_space *mapping)
+{
+ return test_bit(AS_MF_KEEP_UE_MAPPED, &mapping->flags);
+}
+
+static inline void mapping_set_mf_keep_ue_mapped(struct address_space *mapping)
+{
+ set_bit(AS_MF_KEEP_UE_MAPPED, &mapping->flags);
+}
+
static inline gfp_t mapping_gfp_mask(const struct address_space *mapping)
{
return mapping->gfp_mask;
@@ -1274,6 +1286,18 @@ void replace_page_cache_folio(struct folio *old, struct folio *new);
void delete_from_page_cache_batch(struct address_space *mapping,
struct folio_batch *fbatch);
bool filemap_release_folio(struct folio *folio, gfp_t gfp);
+#ifdef CONFIG_MEMORY_FAILURE
+/*
+ * Provided by memory failure to offline HWPoison-ed folio managed by memfd.
+ */
+void filemap_offline_hwpoison_folio(struct address_space *mapping,
+ struct folio *folio);
+#else
+void filemap_offline_hwpoison_folio(struct address_space *mapping,
+ struct folio *folio)
+{
+}
+#endif
loff_t mapping_seek_hole_data(struct address_space *, loff_t start, loff_t end,
int whence);
diff --git a/include/uapi/linux/memfd.h b/include/uapi/linux/memfd.h
index 273a4e15dfcff..d9875da551b7f 100644
--- a/include/uapi/linux/memfd.h
+++ b/include/uapi/linux/memfd.h
@@ -12,6 +12,12 @@
#define MFD_NOEXEC_SEAL 0x0008U
/* executable */
#define MFD_EXEC 0x0010U
+/*
+ * Keep owned folios mapped when uncorrectable memory errors (UE) causes
+ * memory failure (MF) within the folio. Only at the end of the mapping
+ * will its HWPoison-ed folios be dealt with.
+ */
+#define MFD_MF_KEEP_UE_MAPPED 0x0020U
/*
* Huge page size encoding when MFD_HUGETLB is specified, and a huge page
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 0455119716ec0..dd3bc0b75e059 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -6415,6 +6415,18 @@ static bool hugetlb_pte_stable(struct hstate *h, struct mm_struct *mm, unsigned
return same;
}
+bool hugetlb_should_keep_hwpoison_mapped(struct folio *folio,
+ struct address_space *mapping)
+{
+ if (WARN_ON_ONCE(!folio_test_hugetlb(folio)))
+ return false;
+
+ if (!mapping)
+ return false;
+
+ return mapping_mf_keep_ue_mapped(mapping);
+}
+
static vm_fault_t hugetlb_no_page(struct address_space *mapping,
struct vm_fault *vmf)
{
@@ -6537,9 +6549,11 @@ static vm_fault_t hugetlb_no_page(struct address_space *mapping,
* So we need to block hugepage fault by PG_hwpoison bit check.
*/
if (unlikely(folio_test_hwpoison(folio))) {
- ret = VM_FAULT_HWPOISON_LARGE |
- VM_FAULT_SET_HINDEX(hstate_index(h));
- goto backout_unlocked;
+ if (!mapping_mf_keep_ue_mapped(mapping)) {
+ ret = VM_FAULT_HWPOISON_LARGE |
+ VM_FAULT_SET_HINDEX(hstate_index(h));
+ goto backout_unlocked;
+ }
}
/* Check for page in userfault range. */
diff --git a/mm/memfd.c b/mm/memfd.c
index 1d109c1acf211..bfdde4cf90500 100644
--- a/mm/memfd.c
+++ b/mm/memfd.c
@@ -313,7 +313,8 @@ long memfd_fcntl(struct file *file, unsigned int cmd, unsigned int arg)
#define MFD_NAME_PREFIX_LEN (sizeof(MFD_NAME_PREFIX) - 1)
#define MFD_NAME_MAX_LEN (NAME_MAX - MFD_NAME_PREFIX_LEN)
-#define MFD_ALL_FLAGS (MFD_CLOEXEC | MFD_ALLOW_SEALING | MFD_HUGETLB | MFD_NOEXEC_SEAL | MFD_EXEC)
+#define MFD_ALL_FLAGS (MFD_CLOEXEC | MFD_ALLOW_SEALING | MFD_HUGETLB | \
+ MFD_NOEXEC_SEAL | MFD_EXEC | MFD_MF_KEEP_UE_MAPPED)
static int check_sysctl_memfd_noexec(unsigned int *flags)
{
@@ -387,6 +388,8 @@ static int sanitize_flags(unsigned int *flags_ptr)
if (!(flags & MFD_HUGETLB)) {
if (flags & ~MFD_ALL_FLAGS)
return -EINVAL;
+ if (flags & MFD_MF_KEEP_UE_MAPPED)
+ return -EINVAL;
} else {
/* Allow huge page size encoding in flags. */
if (flags & ~(MFD_ALL_FLAGS |
@@ -447,6 +450,16 @@ static struct file *alloc_file(const char *name, unsigned int flags)
file->f_mode |= FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE;
file->f_flags |= O_LARGEFILE;
+ /*
+ * MFD_MF_KEEP_UE_MAPPED can only be specified in memfd_create; no API
+ * to update it once memfd is created. MFD_MF_KEEP_UE_MAPPED is not
+ * seal-able.
+ *
+ * For now MFD_MF_KEEP_UE_MAPPED is only supported by HugeTLBFS.
+ */
+ if (flags & (MFD_HUGETLB | MFD_MF_KEEP_UE_MAPPED))
+ mapping_set_mf_keep_ue_mapped(file->f_mapping);
+
if (flags & MFD_NOEXEC_SEAL) {
struct inode *inode = file_inode(file);
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 3edebb0cda30b..c5e3e28872797 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -373,11 +373,13 @@ static unsigned long dev_pagemap_mapping_shift(struct vm_area_struct *vma,
* Schedule a process for later kill.
* Uses GFP_ATOMIC allocations to avoid potential recursions in the VM.
*/
-static void __add_to_kill(struct task_struct *tsk, const struct page *p,
+static void __add_to_kill(struct task_struct *tsk, struct page *p,
struct vm_area_struct *vma, struct list_head *to_kill,
unsigned long addr)
{
struct to_kill *tk;
+ struct folio *folio;
+ struct address_space *mapping;
tk = kmalloc(sizeof(struct to_kill), GFP_ATOMIC);
if (!tk) {
@@ -388,8 +390,19 @@ static void __add_to_kill(struct task_struct *tsk, const struct page *p,
tk->addr = addr;
if (is_zone_device_page(p))
tk->size_shift = dev_pagemap_mapping_shift(vma, tk->addr);
- else
- tk->size_shift = folio_shift(page_folio(p));
+ else {
+ folio = page_folio(p);
+ mapping = folio_mapping(folio);
+ if (mapping && mapping_mf_keep_ue_mapped(mapping))
+ /*
+ * Let userspace know the radius of HWPoison is
+ * the size of raw page; accessing other pages
+ * inside the folio is still ok.
+ */
+ tk->size_shift = PAGE_SHIFT;
+ else
+ tk->size_shift = folio_shift(folio);
+ }
/*
* Send SIGKILL if "tk->addr == -EFAULT". Also, as
@@ -414,7 +427,7 @@ static void __add_to_kill(struct task_struct *tsk, const struct page *p,
list_add_tail(&tk->nd, to_kill);
}
-static void add_to_kill_anon_file(struct task_struct *tsk, const struct page *p,
+static void add_to_kill_anon_file(struct task_struct *tsk, struct page *p,
struct vm_area_struct *vma, struct list_head *to_kill,
unsigned long addr)
{
@@ -535,7 +548,7 @@ struct task_struct *task_early_kill(struct task_struct *tsk, int force_early)
* Collect processes when the error hit an anonymous page.
*/
static void collect_procs_anon(const struct folio *folio,
- const struct page *page, struct list_head *to_kill,
+ struct page *page, struct list_head *to_kill,
int force_early)
{
struct task_struct *tsk;
@@ -573,7 +586,7 @@ static void collect_procs_anon(const struct folio *folio,
* Collect processes when the error hit a file mapped page.
*/
static void collect_procs_file(const struct folio *folio,
- const struct page *page, struct list_head *to_kill,
+ struct page *page, struct list_head *to_kill,
int force_early)
{
struct vm_area_struct *vma;
@@ -655,7 +668,7 @@ static void collect_procs_fsdax(const struct page *page,
/*
* Collect the processes who have the corrupted page mapped to kill.
*/
-static void collect_procs(const struct folio *folio, const struct page *page,
+static void collect_procs(const struct folio *folio, struct page *page,
struct list_head *tokill, int force_early)
{
if (!folio->mapping)
@@ -1173,6 +1186,13 @@ static int me_huge_page(struct page_state *ps, struct page *p)
}
}
+ /*
+ * MF still needs to holds a refcount for the deferred actions in
+ * filemap_offline_hwpoison_folio.
+ */
+ if (hugetlb_should_keep_hwpoison_mapped(folio, mapping))
+ return res;
+
if (has_extra_refcount(ps, p, extra_pins))
res = MF_FAILED;
@@ -1569,6 +1589,7 @@ static bool hwpoison_user_mappings(struct folio *folio, struct page *p,
{
LIST_HEAD(tokill);
bool unmap_success;
+ bool keep_mapped;
int forcekill;
bool mlocked = folio_test_mlocked(folio);
@@ -1596,8 +1617,12 @@ static bool hwpoison_user_mappings(struct folio *folio, struct page *p,
*/
collect_procs(folio, p, &tokill, flags & MF_ACTION_REQUIRED);
- unmap_success = !unmap_poisoned_folio(folio, pfn, flags & MF_MUST_KILL);
- if (!unmap_success)
+ keep_mapped = hugetlb_should_keep_hwpoison_mapped(folio, folio->mapping);
+ if (!keep_mapped)
+ unmap_poisoned_folio(folio, pfn, flags & MF_MUST_KILL);
+
+ unmap_success = !folio_mapped(folio);
+ if (!keep_mapped && !unmap_success)
pr_err("%#lx: failed to unmap page (folio mapcount=%d)\n",
pfn, folio_mapcount(folio));
@@ -1622,7 +1647,7 @@ static bool hwpoison_user_mappings(struct folio *folio, struct page *p,
!unmap_success;
kill_procs(&tokill, forcekill, pfn, flags);
- return unmap_success;
+ return unmap_success || keep_mapped;
}
static int identify_page_state(unsigned long pfn, struct page *p,
@@ -1862,6 +1887,13 @@ static unsigned long __folio_free_raw_hwp(struct folio *folio, bool move_flag)
unsigned long count = 0;
head = llist_del_all(raw_hwp_list_head(folio));
+ /*
+ * If filemap_offline_hwpoison_folio_hugetlb is handling this folio,
+ * it has already taken off the head of the llist.
+ */
+ if (head == NULL)
+ return 0;
+
llist_for_each_entry_safe(p, next, head, node) {
if (move_flag)
SetPageHWPoison(p->page);
@@ -1878,7 +1910,8 @@ static int folio_set_hugetlb_hwpoison(struct folio *folio, struct page *page)
struct llist_head *head;
struct raw_hwp_page *raw_hwp;
struct raw_hwp_page *p;
- int ret = folio_test_set_hwpoison(folio) ? -EHWPOISON : 0;
+ struct address_space *mapping = folio->mapping;
+ bool has_hwpoison = folio_test_set_hwpoison(folio);
/*
* Once the hwpoison hugepage has lost reliable raw error info,
@@ -1897,8 +1930,15 @@ static int folio_set_hugetlb_hwpoison(struct folio *folio, struct page *page)
if (raw_hwp) {
raw_hwp->page = page;
llist_add(&raw_hwp->node, head);
+ if (hugetlb_should_keep_hwpoison_mapped(folio, mapping))
+ /*
+ * A new raw HWPoison page. Don't return HWPOISON.
+ * Error event will be counted in action_result().
+ */
+ return 0;
+
/* the first error event will be counted in action_result(). */
- if (ret)
+ if (has_hwpoison)
num_poisoned_pages_inc(page_to_pfn(page));
} else {
/*
@@ -1913,7 +1953,8 @@ static int folio_set_hugetlb_hwpoison(struct folio *folio, struct page *page)
*/
__folio_free_raw_hwp(folio, false);
}
- return ret;
+
+ return has_hwpoison ? -EHWPOISON : 0;
}
static unsigned long folio_free_raw_hwp(struct folio *folio, bool move_flag)
@@ -2002,6 +2043,63 @@ int __get_huge_page_for_hwpoison(unsigned long pfn, int flags,
return ret;
}
+static void filemap_offline_hwpoison_folio_hugetlb(struct folio *folio)
+{
+ int ret;
+ struct llist_node *head;
+ struct raw_hwp_page *curr, *next;
+ struct page *page;
+ unsigned long pfn;
+
+ /*
+ * Since folio is still in the folio_batch, drop the refcount
+ * elevated by filemap_get_folios.
+ */
+ folio_put_refs(folio, 1);
+ head = llist_del_all(raw_hwp_list_head(folio));
+
+ /*
+ * Release refcounts held by try_memory_failure_hugetlb, one per
+ * HWPoison-ed page in the raw hwp list.
+ */
+ llist_for_each_entry(curr, head, node) {
+ SetPageHWPoison(curr->page);
+ folio_put(folio);
+ }
+
+ /* Refcount now should be zero and ready to dissolve folio. */
+ ret = dissolve_free_hugetlb_folio(folio);
+ if (ret) {
+ pr_err("failed to dissolve hugetlb folio: %d\n", ret);
+ return;
+ }
+
+ llist_for_each_entry_safe(curr, next, head, node) {
+ page = curr->page;
+ pfn = page_to_pfn(page);
+ drain_all_pages(page_zone(page));
+ if (!take_page_off_buddy(page))
+ pr_err("%#lx: unable to take off buddy allocator\n", pfn);
+
+ page_ref_inc(page);
+ kfree(curr);
+ pr_info("%#lx: pending hard offline completed\n", pfn);
+ }
+}
+
+void filemap_offline_hwpoison_folio(struct address_space *mapping,
+ struct folio *folio)
+{
+ WARN_ON_ONCE(!mapping);
+
+ if (!folio_test_hwpoison(folio))
+ return;
+
+ /* Pending MFR currently only exist for hugetlb. */
+ if (hugetlb_should_keep_hwpoison_mapped(folio, mapping))
+ filemap_offline_hwpoison_folio_hugetlb(folio);
+}
+
/*
* Taking refcount of hugetlb pages needs extra care about race conditions
* with basic operations like hugepage allocation/free/demotion.
--
2.52.0.rc1.455.g30608eb744-googHi, Jiaqi,
Thanks for the work, my comments inline.
On 11/15/2025 5:32 PM, Jiaqi Yan wrote:
> Sometimes immediately hard offlining a large chunk of contigous memory
> having uncorrected memory errors (UE) may not be the best option.
> Cloud providers usually serve capacity- and performance-critical guest
> memory with 1G HugeTLB hugepages, as this significantly reduces the
> overhead associated with managing page tables and TLB misses. However,
> for today's HugeTLB system, once a byte of memory in a hugepage is
> hardware corrupted, the kernel discards the whole hugepage, including
> the healthy portion. Customer workload running in the VM can hardly
> recover from such a great loss of memory.
>
> Therefore keeping or discarding a large chunk of contiguous memory
> owned by userspace (particularly to serve guest memory) due to
> recoverable UE may better be controlled by userspace process
> that owns the memory, e.g. VMM in Cloud environment.
>
> Introduce a memfd-based userspace memory failure (MFR) policy,
> MFD_MF_KEEP_UE_MAPPED. It is intended to be supported for other memfd,
> but the current implementation only covers HugeTLB.
>
> For any hugepage associated with the MFD_MF_KEEP_UE_MAPPED enabled memfd,
> whenever it runs into a UE, MFR doesn't hard offline the HWPoison-ed
> huge folio. IOW the HWPoison-ed memory remains accessible via the memory
> mapping created with that memfd. MFR still sends SIGBUS to the process
> as required. MFR also still maintains HWPoison metadata for the hugepage
> having the UE.
>
> A HWPoison-ed hugepage will be immediately isolated and prevented from
> future allocation once userspace truncates it via the memfd, or the
> owning memfd is closed.
>
> By default MFD_MF_KEEP_UE_MAPPED is not set, and MFR hard offlines
> hugepages having UEs.
>
> Tested with selftest in the follow-up commit.
>
> Signed-off-by: Jiaqi Yan <jiaqiyan@google.com>
> Tested-by: William Roche <william.roche@oracle.com>
> ---
> fs/hugetlbfs/inode.c | 25 +++++++-
> include/linux/hugetlb.h | 7 +++
> include/linux/pagemap.h | 24 +++++++
> include/uapi/linux/memfd.h | 6 ++
> mm/hugetlb.c | 20 +++++-
> mm/memfd.c | 15 ++++-
> mm/memory-failure.c | 124 +++++++++++++++++++++++++++++++++----
> 7 files changed, 202 insertions(+), 19 deletions(-)
>
> diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
> index f42548ee9083c..f8a5aa091d51d 100644
> --- a/fs/hugetlbfs/inode.c
> +++ b/fs/hugetlbfs/inode.c
> @@ -532,6 +532,18 @@ static bool remove_inode_single_folio(struct hstate *h, struct inode *inode,
> }
>
> folio_unlock(folio);
> +
> + /*
> + * There may be pending HWPoison-ed folios when a memfd is being
> + * removed or part of it is being truncated.
> + *
> + * HugeTLBFS' error_remove_folio keeps the HWPoison-ed folios in
> + * page cache until mm wants to drop the folio at the end of the
> + * of the filemap. At this point, if memory failure was delayed
> + * by MFD_MF_KEEP_UE_MAPPED in the past, we can now deal with it.
> + */
> + filemap_offline_hwpoison_folio(mapping, folio);
> +
> return ret;
> }
Looks okay.
>
> @@ -563,13 +575,13 @@ static void remove_inode_hugepages(struct inode *inode, loff_t lstart,
> const pgoff_t end = lend >> PAGE_SHIFT;
> struct folio_batch fbatch;
> pgoff_t next, index;
> - int i, freed = 0;
> + int i, j, freed = 0;
> bool truncate_op = (lend == LLONG_MAX);
>
> folio_batch_init(&fbatch);
> next = lstart >> PAGE_SHIFT;
> while (filemap_get_folios(mapping, &next, end - 1, &fbatch)) {
> - for (i = 0; i < folio_batch_count(&fbatch); ++i) {
> + for (i = 0, j = 0; i < folio_batch_count(&fbatch); ++i) {
> struct folio *folio = fbatch.folios[i];
> u32 hash = 0;
>
> @@ -584,8 +596,17 @@ static void remove_inode_hugepages(struct inode *inode, loff_t lstart,
> index, truncate_op))
> freed++;
>
> + /*
> + * Skip HWPoison-ed hugepages, which should no
> + * longer be hugetlb if successfully dissolved.
> + */
> + if (folio_test_hugetlb(folio))
> + fbatch.folios[j++] = folio;
> +
> mutex_unlock(&hugetlb_fault_mutex_table[hash]);
> }
> + fbatch.nr = j;
> +
> folio_batch_release(&fbatch);
> cond_resched();
> }
Looks okay.
But this reminds me that for now remove_inode_single_folio() has no path
to return 'false' anyway, and if it does, remove_inode_hugepages() will
be broken since it has no logic to account for failed to be
removed folios. Do you mind to make remove_inode_single_folio() a void
function in order to avoid the confusion?
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index 8e63e46b8e1f0..b7733ef5ee917 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -871,10 +871,17 @@ int dissolve_free_hugetlb_folios(unsigned long start_pfn,
>
> #ifdef CONFIG_MEMORY_FAILURE
> extern void folio_clear_hugetlb_hwpoison(struct folio *folio);
> +extern bool hugetlb_should_keep_hwpoison_mapped(struct folio *folio,
> + struct address_space *mapping);
> #else
> static inline void folio_clear_hugetlb_hwpoison(struct folio *folio)
> {
> }
> +static inline bool hugetlb_should_keep_hwpoison_mapped(struct folio *folio
> + struct address_space *mapping)
> +{
> + return false;
> +}
> #endif
It appears that hugetlb_should_keep_hwpoison_mapped() is only called
within mm/memory-failure.c. How about moving it there ?
>
> #ifdef CONFIG_ARCH_ENABLE_HUGEPAGE_MIGRATION
> diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
> index 09b581c1d878d..9ad511aacde7c 100644
> --- a/include/linux/pagemap.h
> +++ b/include/linux/pagemap.h
> @@ -213,6 +213,8 @@ enum mapping_flags {
> AS_WRITEBACK_MAY_DEADLOCK_ON_RECLAIM = 9,
> AS_KERNEL_FILE = 10, /* mapping for a fake kernel file that shouldn't
> account usage to user cgroups */
> + /* For MFD_MF_KEEP_UE_MAPPED. */
> + AS_MF_KEEP_UE_MAPPED = 11,
> /* Bits 16-25 are used for FOLIO_ORDER */
> AS_FOLIO_ORDER_BITS = 5,
> AS_FOLIO_ORDER_MIN = 16,
> @@ -348,6 +350,16 @@ static inline bool mapping_writeback_may_deadlock_on_reclaim(const struct addres
> return test_bit(AS_WRITEBACK_MAY_DEADLOCK_ON_RECLAIM, &mapping->flags);
> }
>
Okay.
> +static inline bool mapping_mf_keep_ue_mapped(const struct address_space *mapping)
> +{
> + return test_bit(AS_MF_KEEP_UE_MAPPED, &mapping->flags);
> +}
> +
> +static inline void mapping_set_mf_keep_ue_mapped(struct address_space *mapping)
> +{
> + set_bit(AS_MF_KEEP_UE_MAPPED, &mapping->flags);
> +}
> +
> static inline gfp_t mapping_gfp_mask(const struct address_space *mapping)
> {
> return mapping->gfp_mask;
> @@ -1274,6 +1286,18 @@ void replace_page_cache_folio(struct folio *old, struct folio *new);
> void delete_from_page_cache_batch(struct address_space *mapping,
> struct folio_batch *fbatch);
> bool filemap_release_folio(struct folio *folio, gfp_t gfp);
> +#ifdef CONFIG_MEMORY_FAILURE
> +/*
> + * Provided by memory failure to offline HWPoison-ed folio managed by memfd.
> + */
> +void filemap_offline_hwpoison_folio(struct address_space *mapping,
> + struct folio *folio);
> +#else
> +void filemap_offline_hwpoison_folio(struct address_space *mapping,
> + struct folio *folio)
> +{
> +}
> +#endif
Okay.
> loff_t mapping_seek_hole_data(struct address_space *, loff_t start, loff_t end,
> int whence);
>
> diff --git a/include/uapi/linux/memfd.h b/include/uapi/linux/memfd.h
> index 273a4e15dfcff..d9875da551b7f 100644
> --- a/include/uapi/linux/memfd.h
> +++ b/include/uapi/linux/memfd.h
> @@ -12,6 +12,12 @@
> #define MFD_NOEXEC_SEAL 0x0008U
> /* executable */
> #define MFD_EXEC 0x0010U
> +/*
> + * Keep owned folios mapped when uncorrectable memory errors (UE) causes
> + * memory failure (MF) within the folio. Only at the end of the mapping
> + * will its HWPoison-ed folios be dealt with.
> + */
> +#define MFD_MF_KEEP_UE_MAPPED 0x0020U
>
> /*
> * Huge page size encoding when MFD_HUGETLB is specified, and a huge page
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 0455119716ec0..dd3bc0b75e059 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -6415,6 +6415,18 @@ static bool hugetlb_pte_stable(struct hstate *h, struct mm_struct *mm, unsigned
> return same;
> }
>
> +bool hugetlb_should_keep_hwpoison_mapped(struct folio *folio,
> + struct address_space *mapping)
> +{
> + if (WARN_ON_ONCE(!folio_test_hugetlb(folio)))
> + return false;
> +
> + if (!mapping)
> + return false;
> +
> + return mapping_mf_keep_ue_mapped(mapping);
> +}
> +
Okay.
> static vm_fault_t hugetlb_no_page(struct address_space *mapping,
> struct vm_fault *vmf)
> {
> @@ -6537,9 +6549,11 @@ static vm_fault_t hugetlb_no_page(struct address_space *mapping,
> * So we need to block hugepage fault by PG_hwpoison bit check.
> */
> if (unlikely(folio_test_hwpoison(folio))) {
> - ret = VM_FAULT_HWPOISON_LARGE |
> - VM_FAULT_SET_HINDEX(hstate_index(h));
> - goto backout_unlocked;
> + if (!mapping_mf_keep_ue_mapped(mapping)) {
> + ret = VM_FAULT_HWPOISON_LARGE |
> + VM_FAULT_SET_HINDEX(hstate_index(h));
> + goto backout_unlocked;
> + }
> }
>
Looks okay, but am curious at Miaohe and others' take.
To allow a known poisoned hugetlb page to be faulted in is for the sake
of capacity, so this, versus a SIGBUS from the MF handler indicating a
disruption and loss of both data and capacity.
No strong opinion here, just wondering if there is any merit to limit
the scope to the MF handler only.
> /* Check for page in userfault range. */
> diff --git a/mm/memfd.c b/mm/memfd.c
> index 1d109c1acf211..bfdde4cf90500 100644
> --- a/mm/memfd.c
> +++ b/mm/memfd.c
> @@ -313,7 +313,8 @@ long memfd_fcntl(struct file *file, unsigned int cmd, unsigned int arg)
> #define MFD_NAME_PREFIX_LEN (sizeof(MFD_NAME_PREFIX) - 1)
> #define MFD_NAME_MAX_LEN (NAME_MAX - MFD_NAME_PREFIX_LEN)
>
> -#define MFD_ALL_FLAGS (MFD_CLOEXEC | MFD_ALLOW_SEALING | MFD_HUGETLB | MFD_NOEXEC_SEAL | MFD_EXEC)
> +#define MFD_ALL_FLAGS (MFD_CLOEXEC | MFD_ALLOW_SEALING | MFD_HUGETLB | \
> + MFD_NOEXEC_SEAL | MFD_EXEC | MFD_MF_KEEP_UE_MAPPED)
>
> static int check_sysctl_memfd_noexec(unsigned int *flags)
> {
> @@ -387,6 +388,8 @@ static int sanitize_flags(unsigned int *flags_ptr)
> if (!(flags & MFD_HUGETLB)) {
> if (flags & ~MFD_ALL_FLAGS)
> return -EINVAL;
> + if (flags & MFD_MF_KEEP_UE_MAPPED)
> + return -EINVAL;
> } else {
> /* Allow huge page size encoding in flags. */
> if (flags & ~(MFD_ALL_FLAGS |
> @@ -447,6 +450,16 @@ static struct file *alloc_file(const char *name, unsigned int flags)
> file->f_mode |= FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE;
> file->f_flags |= O_LARGEFILE;
>
> + /*
> + * MFD_MF_KEEP_UE_MAPPED can only be specified in memfd_create; no API
> + * to update it once memfd is created. MFD_MF_KEEP_UE_MAPPED is not
> + * seal-able.
> + *
> + * For now MFD_MF_KEEP_UE_MAPPED is only supported by HugeTLBFS.
> + */
> + if (flags & (MFD_HUGETLB | MFD_MF_KEEP_UE_MAPPED))
> + mapping_set_mf_keep_ue_mapped(file->f_mapping);
> +
> if (flags & MFD_NOEXEC_SEAL) {
> struct inode *inode = file_inode(file);
>
Okay.
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 3edebb0cda30b..c5e3e28872797 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -373,11 +373,13 @@ static unsigned long dev_pagemap_mapping_shift(struct vm_area_struct *vma,
> * Schedule a process for later kill.
> * Uses GFP_ATOMIC allocations to avoid potential recursions in the VM.
> */
> -static void __add_to_kill(struct task_struct *tsk, const struct page *p,
> +static void __add_to_kill(struct task_struct *tsk, struct page *p,
> struct vm_area_struct *vma, struct list_head *to_kill,
> unsigned long addr)
> {
> struct to_kill *tk;
> + struct folio *folio;
> + struct address_space *mapping;
>
> tk = kmalloc(sizeof(struct to_kill), GFP_ATOMIC);
> if (!tk) {
> @@ -388,8 +390,19 @@ static void __add_to_kill(struct task_struct *tsk, const struct page *p,
> tk->addr = addr;
> if (is_zone_device_page(p))
> tk->size_shift = dev_pagemap_mapping_shift(vma, tk->addr);
> - else
> - tk->size_shift = folio_shift(page_folio(p));
> + else {
> + folio = page_folio(p);
> + mapping = folio_mapping(folio);
> + if (mapping && mapping_mf_keep_ue_mapped(mapping))
> + /*
> + * Let userspace know the radius of HWPoison is
> + * the size of raw page; accessing other pages
> + * inside the folio is still ok.
> + */
> + tk->size_shift = PAGE_SHIFT;
> + else
> + tk->size_shift = folio_shift(folio);
> + }
>
> /*
> * Send SIGKILL if "tk->addr == -EFAULT". Also, as
> @@ -414,7 +427,7 @@ static void __add_to_kill(struct task_struct *tsk, const struct page *p,
> list_add_tail(&tk->nd, to_kill);
> }
>
> -static void add_to_kill_anon_file(struct task_struct *tsk, const struct page *p,
> +static void add_to_kill_anon_file(struct task_struct *tsk, struct page *p,
> struct vm_area_struct *vma, struct list_head *to_kill,
> unsigned long addr)
> {
> @@ -535,7 +548,7 @@ struct task_struct *task_early_kill(struct task_struct *tsk, int force_early)
> * Collect processes when the error hit an anonymous page.
> */
> static void collect_procs_anon(const struct folio *folio,
> - const struct page *page, struct list_head *to_kill,
> + struct page *page, struct list_head *to_kill,
> int force_early)
> {
> struct task_struct *tsk;
> @@ -573,7 +586,7 @@ static void collect_procs_anon(const struct folio *folio,
> * Collect processes when the error hit a file mapped page.
> */
> static void collect_procs_file(const struct folio *folio,
> - const struct page *page, struct list_head *to_kill,
> + struct page *page, struct list_head *to_kill,
> int force_early)
> {
> struct vm_area_struct *vma;
> @@ -655,7 +668,7 @@ static void collect_procs_fsdax(const struct page *page,
> /*
> * Collect the processes who have the corrupted page mapped to kill.
> */
> -static void collect_procs(const struct folio *folio, const struct page *page,
> +static void collect_procs(const struct folio *folio, struct page *page,
> struct list_head *tokill, int force_early)
> {
> if (!folio->mapping)
> @@ -1173,6 +1186,13 @@ static int me_huge_page(struct page_state *ps, struct page *p)
> }
> }
>
> + /*
> + * MF still needs to holds a refcount for the deferred actions in
> + * filemap_offline_hwpoison_folio.
> + */
> + if (hugetlb_should_keep_hwpoison_mapped(folio, mapping))
> + return res;
> +
Okay.
> if (has_extra_refcount(ps, p, extra_pins))
> res = MF_FAILED;
>
> @@ -1569,6 +1589,7 @@ static bool hwpoison_user_mappings(struct folio *folio, struct page *p,
> {
> LIST_HEAD(tokill);
> bool unmap_success;
> + bool keep_mapped;
> int forcekill;
> bool mlocked = folio_test_mlocked(folio);
>
> @@ -1596,8 +1617,12 @@ static bool hwpoison_user_mappings(struct folio *folio, struct page *p,
> */
> collect_procs(folio, p, &tokill, flags & MF_ACTION_REQUIRED);
>
> - unmap_success = !unmap_poisoned_folio(folio, pfn, flags & MF_MUST_KILL);
> - if (!unmap_success)
> + keep_mapped = hugetlb_should_keep_hwpoison_mapped(folio, folio->mapping);
> + if (!keep_mapped)
> + unmap_poisoned_folio(folio, pfn, flags & MF_MUST_KILL);
> +
> + unmap_success = !folio_mapped(folio);
> + if (!keep_mapped && !unmap_success)
> pr_err("%#lx: failed to unmap page (folio mapcount=%d)\n",
> pfn, folio_mapcount(folio));
>
> @@ -1622,7 +1647,7 @@ static bool hwpoison_user_mappings(struct folio *folio, struct page *p,
> !unmap_success;
> kill_procs(&tokill, forcekill, pfn, flags);
>
> - return unmap_success;
> + return unmap_success || keep_mapped;
> }
Okay.
>
> static int identify_page_state(unsigned long pfn, struct page *p,
> @@ -1862,6 +1887,13 @@ static unsigned long __folio_free_raw_hwp(struct folio *folio, bool move_flag)
> unsigned long count = 0;
>
> head = llist_del_all(raw_hwp_list_head(folio));
> + /*
> + * If filemap_offline_hwpoison_folio_hugetlb is handling this folio,
> + * it has already taken off the head of the llist.
> + */
> + if (head == NULL)
> + return 0;
> +
> llist_for_each_entry_safe(p, next, head, node) {
> if (move_flag)
> SetPageHWPoison(p->page);
> @@ -1878,7 +1910,8 @@ static int folio_set_hugetlb_hwpoison(struct folio *folio, struct page *page)
> struct llist_head *head;
> struct raw_hwp_page *raw_hwp;
> struct raw_hwp_page *p;
> - int ret = folio_test_set_hwpoison(folio) ? -EHWPOISON : 0;
> + struct address_space *mapping = folio->mapping;
> + bool has_hwpoison = folio_test_set_hwpoison(folio);
>
> /*
> * Once the hwpoison hugepage has lost reliable raw error info,
> @@ -1897,8 +1930,15 @@ static int folio_set_hugetlb_hwpoison(struct folio *folio, struct page *page)
> if (raw_hwp) {
> raw_hwp->page = page;
> llist_add(&raw_hwp->node, head);
> + if (hugetlb_should_keep_hwpoison_mapped(folio, mapping))
> + /*
> + * A new raw HWPoison page. Don't return HWPOISON.
> + * Error event will be counted in action_result().
> + */
> + return 0;
> +
> /* the first error event will be counted in action_result(). */
> - if (ret)
> + if (has_hwpoison)
> num_poisoned_pages_inc(page_to_pfn(page));
> } else {
> /*
> @@ -1913,7 +1953,8 @@ static int folio_set_hugetlb_hwpoison(struct folio *folio, struct page *page)
> */
> __folio_free_raw_hwp(folio, false);
> }
> - return ret;
> +
> + return has_hwpoison ? -EHWPOISON : 0;
> }
Okay.
>
> static unsigned long folio_free_raw_hwp(struct folio *folio, bool move_flag)
> @@ -2002,6 +2043,63 @@ int __get_huge_page_for_hwpoison(unsigned long pfn, int flags,
> return ret;
> }
>
> +static void filemap_offline_hwpoison_folio_hugetlb(struct folio *folio)
> +{
> + int ret;
> + struct llist_node *head;
> + struct raw_hwp_page *curr, *next;
> + struct page *page;
> + unsigned long pfn;
> +
> + /*
> + * Since folio is still in the folio_batch, drop the refcount
> + * elevated by filemap_get_folios.
> + */
> + folio_put_refs(folio, 1);
> + head = llist_del_all(raw_hwp_list_head(folio));
> +
> + /*
> + * Release refcounts held by try_memory_failure_hugetlb, one per
> + * HWPoison-ed page in the raw hwp list.
> + */
> + llist_for_each_entry(curr, head, node) {
> + SetPageHWPoison(curr->page);
> + folio_put(folio);
> + }
> +
> + /* Refcount now should be zero and ready to dissolve folio. */
> + ret = dissolve_free_hugetlb_folio(folio);
> + if (ret) {
> + pr_err("failed to dissolve hugetlb folio: %d\n", ret);
> + return;
> + }
> +
> + llist_for_each_entry_safe(curr, next, head, node) {
> + page = curr->page;
> + pfn = page_to_pfn(page);
> + drain_all_pages(page_zone(page));
> + if (!take_page_off_buddy(page))
> + pr_err("%#lx: unable to take off buddy allocator\n", pfn);
> +
> + page_ref_inc(page);
> + kfree(curr);
> + pr_info("%#lx: pending hard offline completed\n", pfn);
> + }
> +}
> +
> +void filemap_offline_hwpoison_folio(struct address_space *mapping,
> + struct folio *folio)
> +{
> + WARN_ON_ONCE(!mapping);
> +
> + if (!folio_test_hwpoison(folio))
> + return;
> +
> + /* Pending MFR currently only exist for hugetlb. */
> + if (hugetlb_should_keep_hwpoison_mapped(folio, mapping))
> + filemap_offline_hwpoison_folio_hugetlb(folio);
> +}
> +
> /*
> * Taking refcount of hugetlb pages needs extra care about race conditions
> * with basic operations like hugepage allocation/free/demotion.
Looks good.
thanks,
-jane
Hi Jane,
Thanks for your reviews, I should be able to address your comments in v3.
On Tue, Dec 2, 2025 at 8:11 PM <jane.chu@oracle.com> wrote:
>
> Hi, Jiaqi,
>
> Thanks for the work, my comments inline.
>
> On 11/15/2025 5:32 PM, Jiaqi Yan wrote:
> > Sometimes immediately hard offlining a large chunk of contigous memory
> > having uncorrected memory errors (UE) may not be the best option.
> > Cloud providers usually serve capacity- and performance-critical guest
> > memory with 1G HugeTLB hugepages, as this significantly reduces the
> > overhead associated with managing page tables and TLB misses. However,
> > for today's HugeTLB system, once a byte of memory in a hugepage is
> > hardware corrupted, the kernel discards the whole hugepage, including
> > the healthy portion. Customer workload running in the VM can hardly
> > recover from such a great loss of memory.
> >
> > Therefore keeping or discarding a large chunk of contiguous memory
> > owned by userspace (particularly to serve guest memory) due to
> > recoverable UE may better be controlled by userspace process
> > that owns the memory, e.g. VMM in Cloud environment.
> >
> > Introduce a memfd-based userspace memory failure (MFR) policy,
> > MFD_MF_KEEP_UE_MAPPED. It is intended to be supported for other memfd,
> > but the current implementation only covers HugeTLB.
> >
> > For any hugepage associated with the MFD_MF_KEEP_UE_MAPPED enabled memfd,
> > whenever it runs into a UE, MFR doesn't hard offline the HWPoison-ed
> > huge folio. IOW the HWPoison-ed memory remains accessible via the memory
> > mapping created with that memfd. MFR still sends SIGBUS to the process
> > as required. MFR also still maintains HWPoison metadata for the hugepage
> > having the UE.
> >
> > A HWPoison-ed hugepage will be immediately isolated and prevented from
> > future allocation once userspace truncates it via the memfd, or the
> > owning memfd is closed.
> >
> > By default MFD_MF_KEEP_UE_MAPPED is not set, and MFR hard offlines
> > hugepages having UEs.
> >
> > Tested with selftest in the follow-up commit.
> >
> > Signed-off-by: Jiaqi Yan <jiaqiyan@google.com>
> > Tested-by: William Roche <william.roche@oracle.com>
> > ---
> > fs/hugetlbfs/inode.c | 25 +++++++-
> > include/linux/hugetlb.h | 7 +++
> > include/linux/pagemap.h | 24 +++++++
> > include/uapi/linux/memfd.h | 6 ++
> > mm/hugetlb.c | 20 +++++-
> > mm/memfd.c | 15 ++++-
> > mm/memory-failure.c | 124 +++++++++++++++++++++++++++++++++----
> > 7 files changed, 202 insertions(+), 19 deletions(-)
> >
> > diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
> > index f42548ee9083c..f8a5aa091d51d 100644
> > --- a/fs/hugetlbfs/inode.c
> > +++ b/fs/hugetlbfs/inode.c
> > @@ -532,6 +532,18 @@ static bool remove_inode_single_folio(struct hstate *h, struct inode *inode,
> > }
> >
> > folio_unlock(folio);
> > +
> > + /*
> > + * There may be pending HWPoison-ed folios when a memfd is being
> > + * removed or part of it is being truncated.
> > + *
> > + * HugeTLBFS' error_remove_folio keeps the HWPoison-ed folios in
> > + * page cache until mm wants to drop the folio at the end of the
> > + * of the filemap. At this point, if memory failure was delayed
> > + * by MFD_MF_KEEP_UE_MAPPED in the past, we can now deal with it.
> > + */
> > + filemap_offline_hwpoison_folio(mapping, folio);
> > +
> > return ret;
> > }
>
> Looks okay.
>
> >
> > @@ -563,13 +575,13 @@ static void remove_inode_hugepages(struct inode *inode, loff_t lstart,
> > const pgoff_t end = lend >> PAGE_SHIFT;
> > struct folio_batch fbatch;
> > pgoff_t next, index;
> > - int i, freed = 0;
> > + int i, j, freed = 0;
> > bool truncate_op = (lend == LLONG_MAX);
> >
> > folio_batch_init(&fbatch);
> > next = lstart >> PAGE_SHIFT;
> > while (filemap_get_folios(mapping, &next, end - 1, &fbatch)) {
> > - for (i = 0; i < folio_batch_count(&fbatch); ++i) {
> > + for (i = 0, j = 0; i < folio_batch_count(&fbatch); ++i) {
> > struct folio *folio = fbatch.folios[i];
> > u32 hash = 0;
> >
> > @@ -584,8 +596,17 @@ static void remove_inode_hugepages(struct inode *inode, loff_t lstart,
> > index, truncate_op))
> > freed++;
> >
> > + /*
> > + * Skip HWPoison-ed hugepages, which should no
> > + * longer be hugetlb if successfully dissolved.
> > + */
> > + if (folio_test_hugetlb(folio))
> > + fbatch.folios[j++] = folio;
> > +
> > mutex_unlock(&hugetlb_fault_mutex_table[hash]);
> > }
> > + fbatch.nr = j;
> > +
> > folio_batch_release(&fbatch);
> > cond_resched();
> > }
>
> Looks okay.
>
> But this reminds me that for now remove_inode_single_folio() has no path
> to return 'false' anyway, and if it does, remove_inode_hugepages() will
> be broken since it has no logic to account for failed to be
> removed folios. Do you mind to make remove_inode_single_folio() a void
> function in order to avoid the confusion?
Aha, looks like so. Let me do it in a new commit for clarity.
>
>
> > diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> > index 8e63e46b8e1f0..b7733ef5ee917 100644
> > --- a/include/linux/hugetlb.h
> > +++ b/include/linux/hugetlb.h
> > @@ -871,10 +871,17 @@ int dissolve_free_hugetlb_folios(unsigned long start_pfn,
> >
> > #ifdef CONFIG_MEMORY_FAILURE
> > extern void folio_clear_hugetlb_hwpoison(struct folio *folio);
> > +extern bool hugetlb_should_keep_hwpoison_mapped(struct folio *folio,
> > + struct address_space *mapping);
> > #else
> > static inline void folio_clear_hugetlb_hwpoison(struct folio *folio)
> > {
> > }
> > +static inline bool hugetlb_should_keep_hwpoison_mapped(struct folio *folio
> > + struct address_space *mapping)
> > +{
> > + return false;
> > +}
> > #endif
>
> It appears that hugetlb_should_keep_hwpoison_mapped() is only called
> within mm/memory-failure.c. How about moving it there ?
Yep, will do in v3.
>
> >
> > #ifdef CONFIG_ARCH_ENABLE_HUGEPAGE_MIGRATION
> > diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
> > index 09b581c1d878d..9ad511aacde7c 100644
> > --- a/include/linux/pagemap.h
> > +++ b/include/linux/pagemap.h
> > @@ -213,6 +213,8 @@ enum mapping_flags {
> > AS_WRITEBACK_MAY_DEADLOCK_ON_RECLAIM = 9,
> > AS_KERNEL_FILE = 10, /* mapping for a fake kernel file that shouldn't
> > account usage to user cgroups */
> > + /* For MFD_MF_KEEP_UE_MAPPED. */
> > + AS_MF_KEEP_UE_MAPPED = 11,
> > /* Bits 16-25 are used for FOLIO_ORDER */
> > AS_FOLIO_ORDER_BITS = 5,
> > AS_FOLIO_ORDER_MIN = 16,
> > @@ -348,6 +350,16 @@ static inline bool mapping_writeback_may_deadlock_on_reclaim(const struct addres
> > return test_bit(AS_WRITEBACK_MAY_DEADLOCK_ON_RECLAIM, &mapping->flags);
> > }
> >
> Okay.
>
> > +static inline bool mapping_mf_keep_ue_mapped(const struct address_space *mapping)
> > +{
> > + return test_bit(AS_MF_KEEP_UE_MAPPED, &mapping->flags);
> > +}
> > +
> > +static inline void mapping_set_mf_keep_ue_mapped(struct address_space *mapping)
> > +{
> > + set_bit(AS_MF_KEEP_UE_MAPPED, &mapping->flags);
> > +}
> > +
> > static inline gfp_t mapping_gfp_mask(const struct address_space *mapping)
> > {
> > return mapping->gfp_mask;
> > @@ -1274,6 +1286,18 @@ void replace_page_cache_folio(struct folio *old, struct folio *new);
> > void delete_from_page_cache_batch(struct address_space *mapping,
> > struct folio_batch *fbatch);
> > bool filemap_release_folio(struct folio *folio, gfp_t gfp);
> > +#ifdef CONFIG_MEMORY_FAILURE
> > +/*
> > + * Provided by memory failure to offline HWPoison-ed folio managed by memfd.
> > + */
> > +void filemap_offline_hwpoison_folio(struct address_space *mapping,
> > + struct folio *folio);
> > +#else
> > +void filemap_offline_hwpoison_folio(struct address_space *mapping,
> > + struct folio *folio)
> > +{
> > +}
> > +#endif
>
> Okay.
>
> > loff_t mapping_seek_hole_data(struct address_space *, loff_t start, loff_t end,
> > int whence);
> >
> > diff --git a/include/uapi/linux/memfd.h b/include/uapi/linux/memfd.h
> > index 273a4e15dfcff..d9875da551b7f 100644
> > --- a/include/uapi/linux/memfd.h
> > +++ b/include/uapi/linux/memfd.h
> > @@ -12,6 +12,12 @@
> > #define MFD_NOEXEC_SEAL 0x0008U
> > /* executable */
> > #define MFD_EXEC 0x0010U
> > +/*
> > + * Keep owned folios mapped when uncorrectable memory errors (UE) causes
> > + * memory failure (MF) within the folio. Only at the end of the mapping
> > + * will its HWPoison-ed folios be dealt with.
> > + */
> > +#define MFD_MF_KEEP_UE_MAPPED 0x0020U
> >
> > /*
> > * Huge page size encoding when MFD_HUGETLB is specified, and a huge page
> > diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> > index 0455119716ec0..dd3bc0b75e059 100644
> > --- a/mm/hugetlb.c
> > +++ b/mm/hugetlb.c
> > @@ -6415,6 +6415,18 @@ static bool hugetlb_pte_stable(struct hstate *h, struct mm_struct *mm, unsigned
> > return same;
> > }
> >
> > +bool hugetlb_should_keep_hwpoison_mapped(struct folio *folio,
> > + struct address_space *mapping)
> > +{
> > + if (WARN_ON_ONCE(!folio_test_hugetlb(folio)))
> > + return false;
> > +
> > + if (!mapping)
> > + return false;
> > +
> > + return mapping_mf_keep_ue_mapped(mapping);
> > +}
> > +
>
> Okay.
>
> > static vm_fault_t hugetlb_no_page(struct address_space *mapping,
> > struct vm_fault *vmf)
> > {
> > @@ -6537,9 +6549,11 @@ static vm_fault_t hugetlb_no_page(struct address_space *mapping,
> > * So we need to block hugepage fault by PG_hwpoison bit check.
> > */
> > if (unlikely(folio_test_hwpoison(folio))) {
> > - ret = VM_FAULT_HWPOISON_LARGE |
> > - VM_FAULT_SET_HINDEX(hstate_index(h));
> > - goto backout_unlocked;
> > + if (!mapping_mf_keep_ue_mapped(mapping)) {
> > + ret = VM_FAULT_HWPOISON_LARGE |
> > + VM_FAULT_SET_HINDEX(hstate_index(h));
> > + goto backout_unlocked;
> > + }
> > }
> >
>
> Looks okay, but am curious at Miaohe and others' take.
>
> To allow a known poisoned hugetlb page to be faulted in is for the sake
> of capacity, so this, versus a SIGBUS from the MF handler indicating a
> disruption and loss of both data and capacity.
> No strong opinion here, just wondering if there is any merit to limit
> the scope to the MF handler only.
Are you suggesting to prevent hugetlb_no_page() (when a hugepage is
not yet faulted) from faulting in a known HWPoison HugeTLB page?
>
> > /* Check for page in userfault range. */
> > diff --git a/mm/memfd.c b/mm/memfd.c
> > index 1d109c1acf211..bfdde4cf90500 100644
> > --- a/mm/memfd.c
> > +++ b/mm/memfd.c
> > @@ -313,7 +313,8 @@ long memfd_fcntl(struct file *file, unsigned int cmd, unsigned int arg)
> > #define MFD_NAME_PREFIX_LEN (sizeof(MFD_NAME_PREFIX) - 1)
> > #define MFD_NAME_MAX_LEN (NAME_MAX - MFD_NAME_PREFIX_LEN)
> >
> > -#define MFD_ALL_FLAGS (MFD_CLOEXEC | MFD_ALLOW_SEALING | MFD_HUGETLB | MFD_NOEXEC_SEAL | MFD_EXEC)
> > +#define MFD_ALL_FLAGS (MFD_CLOEXEC | MFD_ALLOW_SEALING | MFD_HUGETLB | \
> > + MFD_NOEXEC_SEAL | MFD_EXEC | MFD_MF_KEEP_UE_MAPPED)
> >
> > static int check_sysctl_memfd_noexec(unsigned int *flags)
> > {
> > @@ -387,6 +388,8 @@ static int sanitize_flags(unsigned int *flags_ptr)
> > if (!(flags & MFD_HUGETLB)) {
> > if (flags & ~MFD_ALL_FLAGS)
> > return -EINVAL;
> > + if (flags & MFD_MF_KEEP_UE_MAPPED)
> > + return -EINVAL;
> > } else {
> > /* Allow huge page size encoding in flags. */
> > if (flags & ~(MFD_ALL_FLAGS |
> > @@ -447,6 +450,16 @@ static struct file *alloc_file(const char *name, unsigned int flags)
> > file->f_mode |= FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE;
> > file->f_flags |= O_LARGEFILE;
> >
> > + /*
> > + * MFD_MF_KEEP_UE_MAPPED can only be specified in memfd_create; no API
> > + * to update it once memfd is created. MFD_MF_KEEP_UE_MAPPED is not
> > + * seal-able.
> > + *
> > + * For now MFD_MF_KEEP_UE_MAPPED is only supported by HugeTLBFS.
> > + */
> > + if (flags & (MFD_HUGETLB | MFD_MF_KEEP_UE_MAPPED))
> > + mapping_set_mf_keep_ue_mapped(file->f_mapping);
> > +
> > if (flags & MFD_NOEXEC_SEAL) {
> > struct inode *inode = file_inode(file);
> >
>
> Okay.
>
> > diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> > index 3edebb0cda30b..c5e3e28872797 100644
> > --- a/mm/memory-failure.c
> > +++ b/mm/memory-failure.c
> > @@ -373,11 +373,13 @@ static unsigned long dev_pagemap_mapping_shift(struct vm_area_struct *vma,
> > * Schedule a process for later kill.
> > * Uses GFP_ATOMIC allocations to avoid potential recursions in the VM.
> > */
> > -static void __add_to_kill(struct task_struct *tsk, const struct page *p,
> > +static void __add_to_kill(struct task_struct *tsk, struct page *p,
> > struct vm_area_struct *vma, struct list_head *to_kill,
> > unsigned long addr)
> > {
> > struct to_kill *tk;
> > + struct folio *folio;
> > + struct address_space *mapping;
> >
> > tk = kmalloc(sizeof(struct to_kill), GFP_ATOMIC);
> > if (!tk) {
> > @@ -388,8 +390,19 @@ static void __add_to_kill(struct task_struct *tsk, const struct page *p,
> > tk->addr = addr;
> > if (is_zone_device_page(p))
> > tk->size_shift = dev_pagemap_mapping_shift(vma, tk->addr);
> > - else
> > - tk->size_shift = folio_shift(page_folio(p));
> > + else {
> > + folio = page_folio(p);
> > + mapping = folio_mapping(folio);
> > + if (mapping && mapping_mf_keep_ue_mapped(mapping))
> > + /*
> > + * Let userspace know the radius of HWPoison is
> > + * the size of raw page; accessing other pages
> > + * inside the folio is still ok.
> > + */
> > + tk->size_shift = PAGE_SHIFT;
> > + else
> > + tk->size_shift = folio_shift(folio);
> > + }
> >
> > /*
> > * Send SIGKILL if "tk->addr == -EFAULT". Also, as
> > @@ -414,7 +427,7 @@ static void __add_to_kill(struct task_struct *tsk, const struct page *p,
> > list_add_tail(&tk->nd, to_kill);
> > }
> >
> > -static void add_to_kill_anon_file(struct task_struct *tsk, const struct page *p,
> > +static void add_to_kill_anon_file(struct task_struct *tsk, struct page *p,
> > struct vm_area_struct *vma, struct list_head *to_kill,
> > unsigned long addr)
> > {
> > @@ -535,7 +548,7 @@ struct task_struct *task_early_kill(struct task_struct *tsk, int force_early)
> > * Collect processes when the error hit an anonymous page.
> > */
> > static void collect_procs_anon(const struct folio *folio,
> > - const struct page *page, struct list_head *to_kill,
> > + struct page *page, struct list_head *to_kill,
> > int force_early)
> > {
> > struct task_struct *tsk;
> > @@ -573,7 +586,7 @@ static void collect_procs_anon(const struct folio *folio,
> > * Collect processes when the error hit a file mapped page.
> > */
> > static void collect_procs_file(const struct folio *folio,
> > - const struct page *page, struct list_head *to_kill,
> > + struct page *page, struct list_head *to_kill,
> > int force_early)
> > {
> > struct vm_area_struct *vma;
> > @@ -655,7 +668,7 @@ static void collect_procs_fsdax(const struct page *page,
> > /*
> > * Collect the processes who have the corrupted page mapped to kill.
> > */
> > -static void collect_procs(const struct folio *folio, const struct page *page,
> > +static void collect_procs(const struct folio *folio, struct page *page,
> > struct list_head *tokill, int force_early)
> > {
> > if (!folio->mapping)
> > @@ -1173,6 +1186,13 @@ static int me_huge_page(struct page_state *ps, struct page *p)
> > }
> > }
> >
> > + /*
> > + * MF still needs to holds a refcount for the deferred actions in
> > + * filemap_offline_hwpoison_folio.
> > + */
> > + if (hugetlb_should_keep_hwpoison_mapped(folio, mapping))
> > + return res;
> > +
>
> Okay.
>
> > if (has_extra_refcount(ps, p, extra_pins))
> > res = MF_FAILED;
> >
> > @@ -1569,6 +1589,7 @@ static bool hwpoison_user_mappings(struct folio *folio, struct page *p,
> > {
> > LIST_HEAD(tokill);
> > bool unmap_success;
> > + bool keep_mapped;
> > int forcekill;
> > bool mlocked = folio_test_mlocked(folio);
> >
> > @@ -1596,8 +1617,12 @@ static bool hwpoison_user_mappings(struct folio *folio, struct page *p,
> > */
> > collect_procs(folio, p, &tokill, flags & MF_ACTION_REQUIRED);
> >
> > - unmap_success = !unmap_poisoned_folio(folio, pfn, flags & MF_MUST_KILL);
> > - if (!unmap_success)
> > + keep_mapped = hugetlb_should_keep_hwpoison_mapped(folio, folio->mapping);
> > + if (!keep_mapped)
> > + unmap_poisoned_folio(folio, pfn, flags & MF_MUST_KILL);
> > +
> > + unmap_success = !folio_mapped(folio);
> > + if (!keep_mapped && !unmap_success)
> > pr_err("%#lx: failed to unmap page (folio mapcount=%d)\n",
> > pfn, folio_mapcount(folio));
> >
> > @@ -1622,7 +1647,7 @@ static bool hwpoison_user_mappings(struct folio *folio, struct page *p,
> > !unmap_success;
> > kill_procs(&tokill, forcekill, pfn, flags);
> >
> > - return unmap_success;
> > + return unmap_success || keep_mapped;
> > }
>
> Okay.
>
> >
> > static int identify_page_state(unsigned long pfn, struct page *p,
> > @@ -1862,6 +1887,13 @@ static unsigned long __folio_free_raw_hwp(struct folio *folio, bool move_flag)
> > unsigned long count = 0;
> >
> > head = llist_del_all(raw_hwp_list_head(folio));
> > + /*
> > + * If filemap_offline_hwpoison_folio_hugetlb is handling this folio,
> > + * it has already taken off the head of the llist.
> > + */
> > + if (head == NULL)
> > + return 0;
> > +
> > llist_for_each_entry_safe(p, next, head, node) {
> > if (move_flag)
> > SetPageHWPoison(p->page);
> > @@ -1878,7 +1910,8 @@ static int folio_set_hugetlb_hwpoison(struct folio *folio, struct page *page)
> > struct llist_head *head;
> > struct raw_hwp_page *raw_hwp;
> > struct raw_hwp_page *p;
> > - int ret = folio_test_set_hwpoison(folio) ? -EHWPOISON : 0;
> > + struct address_space *mapping = folio->mapping;
> > + bool has_hwpoison = folio_test_set_hwpoison(folio);
> >
> > /*
> > * Once the hwpoison hugepage has lost reliable raw error info,
> > @@ -1897,8 +1930,15 @@ static int folio_set_hugetlb_hwpoison(struct folio *folio, struct page *page)
> > if (raw_hwp) {
> > raw_hwp->page = page;
> > llist_add(&raw_hwp->node, head);
> > + if (hugetlb_should_keep_hwpoison_mapped(folio, mapping))
> > + /*
> > + * A new raw HWPoison page. Don't return HWPOISON.
> > + * Error event will be counted in action_result().
> > + */
> > + return 0;
> > +
> > /* the first error event will be counted in action_result(). */
> > - if (ret)
> > + if (has_hwpoison)
> > num_poisoned_pages_inc(page_to_pfn(page));
> > } else {
> > /*
> > @@ -1913,7 +1953,8 @@ static int folio_set_hugetlb_hwpoison(struct folio *folio, struct page *page)
> > */
> > __folio_free_raw_hwp(folio, false);
> > }
> > - return ret;
> > +
> > + return has_hwpoison ? -EHWPOISON : 0;
> > }
>
> Okay.
>
> >
> > static unsigned long folio_free_raw_hwp(struct folio *folio, bool move_flag)
> > @@ -2002,6 +2043,63 @@ int __get_huge_page_for_hwpoison(unsigned long pfn, int flags,
> > return ret;
> > }
> >
> > +static void filemap_offline_hwpoison_folio_hugetlb(struct folio *folio)
> > +{
> > + int ret;
> > + struct llist_node *head;
> > + struct raw_hwp_page *curr, *next;
> > + struct page *page;
> > + unsigned long pfn;
> > +
> > + /*
> > + * Since folio is still in the folio_batch, drop the refcount
> > + * elevated by filemap_get_folios.
> > + */
> > + folio_put_refs(folio, 1);
> > + head = llist_del_all(raw_hwp_list_head(folio));
> > +
> > + /*
> > + * Release refcounts held by try_memory_failure_hugetlb, one per
> > + * HWPoison-ed page in the raw hwp list.
> > + */
> > + llist_for_each_entry(curr, head, node) {
> > + SetPageHWPoison(curr->page);
> > + folio_put(folio);
> > + }
> > +
> > + /* Refcount now should be zero and ready to dissolve folio. */
> > + ret = dissolve_free_hugetlb_folio(folio);
> > + if (ret) {
> > + pr_err("failed to dissolve hugetlb folio: %d\n", ret);
> > + return;
> > + }
> > +
> > + llist_for_each_entry_safe(curr, next, head, node) {
> > + page = curr->page;
> > + pfn = page_to_pfn(page);
> > + drain_all_pages(page_zone(page));
> > + if (!take_page_off_buddy(page))
> > + pr_err("%#lx: unable to take off buddy allocator\n", pfn);
> > +
> > + page_ref_inc(page);
> > + kfree(curr);
> > + pr_info("%#lx: pending hard offline completed\n", pfn);
> > + }
> > +}
> > +
> > +void filemap_offline_hwpoison_folio(struct address_space *mapping,
> > + struct folio *folio)
> > +{
> > + WARN_ON_ONCE(!mapping);
> > +
> > + if (!folio_test_hwpoison(folio))
> > + return;
> > +
> > + /* Pending MFR currently only exist for hugetlb. */
> > + if (hugetlb_should_keep_hwpoison_mapped(folio, mapping))
> > + filemap_offline_hwpoison_folio_hugetlb(folio);
> > +}
> > +
> > /*
> > * Taking refcount of hugetlb pages needs extra care about race conditions
> > * with basic operations like hugepage allocation/free/demotion.
>
>
> Looks good.
>
> thanks,
> -jane
On Tue, Dec 2, 2025 at 8:11 PM <jane.chu@oracle.com> wrote:
>
> Hi, Jiaqi,
>
> Thanks for the work, my comments inline.
Thank you both for the thorough and helpful reviews, Jane and William!
I plan to first rework "[PATCH v1 0/2] Only free healthy pages in
high-order HWPoison folio", given it is the key to concerns you have
in this patch. Then I will address your comments on code
quality/readability for this patch.
>
> On 11/15/2025 5:32 PM, Jiaqi Yan wrote:
> > Sometimes immediately hard offlining a large chunk of contigous memory
> > having uncorrected memory errors (UE) may not be the best option.
> > Cloud providers usually serve capacity- and performance-critical guest
> > memory with 1G HugeTLB hugepages, as this significantly reduces the
> > overhead associated with managing page tables and TLB misses. However,
> > for today's HugeTLB system, once a byte of memory in a hugepage is
> > hardware corrupted, the kernel discards the whole hugepage, including
> > the healthy portion. Customer workload running in the VM can hardly
> > recover from such a great loss of memory.
> >
> > Therefore keeping or discarding a large chunk of contiguous memory
> > owned by userspace (particularly to serve guest memory) due to
> > recoverable UE may better be controlled by userspace process
> > that owns the memory, e.g. VMM in Cloud environment.
> >
> > Introduce a memfd-based userspace memory failure (MFR) policy,
> > MFD_MF_KEEP_UE_MAPPED. It is intended to be supported for other memfd,
> > but the current implementation only covers HugeTLB.
> >
> > For any hugepage associated with the MFD_MF_KEEP_UE_MAPPED enabled memfd,
> > whenever it runs into a UE, MFR doesn't hard offline the HWPoison-ed
> > huge folio. IOW the HWPoison-ed memory remains accessible via the memory
> > mapping created with that memfd. MFR still sends SIGBUS to the process
> > as required. MFR also still maintains HWPoison metadata for the hugepage
> > having the UE.
> >
> > A HWPoison-ed hugepage will be immediately isolated and prevented from
> > future allocation once userspace truncates it via the memfd, or the
> > owning memfd is closed.
> >
> > By default MFD_MF_KEEP_UE_MAPPED is not set, and MFR hard offlines
> > hugepages having UEs.
> >
> > Tested with selftest in the follow-up commit.
> >
> > Signed-off-by: Jiaqi Yan <jiaqiyan@google.com>
> > Tested-by: William Roche <william.roche@oracle.com>
> > ---
> > fs/hugetlbfs/inode.c | 25 +++++++-
> > include/linux/hugetlb.h | 7 +++
> > include/linux/pagemap.h | 24 +++++++
> > include/uapi/linux/memfd.h | 6 ++
> > mm/hugetlb.c | 20 +++++-
> > mm/memfd.c | 15 ++++-
> > mm/memory-failure.c | 124 +++++++++++++++++++++++++++++++++----
> > 7 files changed, 202 insertions(+), 19 deletions(-)
> >
> > diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
> > index f42548ee9083c..f8a5aa091d51d 100644
> > --- a/fs/hugetlbfs/inode.c
> > +++ b/fs/hugetlbfs/inode.c
> > @@ -532,6 +532,18 @@ static bool remove_inode_single_folio(struct hstate *h, struct inode *inode,
> > }
> >
> > folio_unlock(folio);
> > +
> > + /*
> > + * There may be pending HWPoison-ed folios when a memfd is being
> > + * removed or part of it is being truncated.
> > + *
> > + * HugeTLBFS' error_remove_folio keeps the HWPoison-ed folios in
> > + * page cache until mm wants to drop the folio at the end of the
> > + * of the filemap. At this point, if memory failure was delayed
> > + * by MFD_MF_KEEP_UE_MAPPED in the past, we can now deal with it.
> > + */
> > + filemap_offline_hwpoison_folio(mapping, folio);
> > +
> > return ret;
> > }
>
> Looks okay.
>
> >
> > @@ -563,13 +575,13 @@ static void remove_inode_hugepages(struct inode *inode, loff_t lstart,
> > const pgoff_t end = lend >> PAGE_SHIFT;
> > struct folio_batch fbatch;
> > pgoff_t next, index;
> > - int i, freed = 0;
> > + int i, j, freed = 0;
> > bool truncate_op = (lend == LLONG_MAX);
> >
> > folio_batch_init(&fbatch);
> > next = lstart >> PAGE_SHIFT;
> > while (filemap_get_folios(mapping, &next, end - 1, &fbatch)) {
> > - for (i = 0; i < folio_batch_count(&fbatch); ++i) {
> > + for (i = 0, j = 0; i < folio_batch_count(&fbatch); ++i) {
> > struct folio *folio = fbatch.folios[i];
> > u32 hash = 0;
> >
> > @@ -584,8 +596,17 @@ static void remove_inode_hugepages(struct inode *inode, loff_t lstart,
> > index, truncate_op))
> > freed++;
> >
> > + /*
> > + * Skip HWPoison-ed hugepages, which should no
> > + * longer be hugetlb if successfully dissolved.
> > + */
> > + if (folio_test_hugetlb(folio))
> > + fbatch.folios[j++] = folio;
> > +
> > mutex_unlock(&hugetlb_fault_mutex_table[hash]);
> > }
> > + fbatch.nr = j;
> > +
> > folio_batch_release(&fbatch);
> > cond_resched();
> > }
>
> Looks okay.
>
> But this reminds me that for now remove_inode_single_folio() has no path
> to return 'false' anyway, and if it does, remove_inode_hugepages() will
> be broken since it has no logic to account for failed to be
> removed folios. Do you mind to make remove_inode_single_folio() a void
> function in order to avoid the confusion?
>
>
> > diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> > index 8e63e46b8e1f0..b7733ef5ee917 100644
> > --- a/include/linux/hugetlb.h
> > +++ b/include/linux/hugetlb.h
> > @@ -871,10 +871,17 @@ int dissolve_free_hugetlb_folios(unsigned long start_pfn,
> >
> > #ifdef CONFIG_MEMORY_FAILURE
> > extern void folio_clear_hugetlb_hwpoison(struct folio *folio);
> > +extern bool hugetlb_should_keep_hwpoison_mapped(struct folio *folio,
> > + struct address_space *mapping);
> > #else
> > static inline void folio_clear_hugetlb_hwpoison(struct folio *folio)
> > {
> > }
> > +static inline bool hugetlb_should_keep_hwpoison_mapped(struct folio *folio
> > + struct address_space *mapping)
> > +{
> > + return false;
> > +}
> > #endif
>
> It appears that hugetlb_should_keep_hwpoison_mapped() is only called
> within mm/memory-failure.c. How about moving it there ?
>
> >
> > #ifdef CONFIG_ARCH_ENABLE_HUGEPAGE_MIGRATION
> > diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
> > index 09b581c1d878d..9ad511aacde7c 100644
> > --- a/include/linux/pagemap.h
> > +++ b/include/linux/pagemap.h
> > @@ -213,6 +213,8 @@ enum mapping_flags {
> > AS_WRITEBACK_MAY_DEADLOCK_ON_RECLAIM = 9,
> > AS_KERNEL_FILE = 10, /* mapping for a fake kernel file that shouldn't
> > account usage to user cgroups */
> > + /* For MFD_MF_KEEP_UE_MAPPED. */
> > + AS_MF_KEEP_UE_MAPPED = 11,
> > /* Bits 16-25 are used for FOLIO_ORDER */
> > AS_FOLIO_ORDER_BITS = 5,
> > AS_FOLIO_ORDER_MIN = 16,
> > @@ -348,6 +350,16 @@ static inline bool mapping_writeback_may_deadlock_on_reclaim(const struct addres
> > return test_bit(AS_WRITEBACK_MAY_DEADLOCK_ON_RECLAIM, &mapping->flags);
> > }
> >
> Okay.
>
> > +static inline bool mapping_mf_keep_ue_mapped(const struct address_space *mapping)
> > +{
> > + return test_bit(AS_MF_KEEP_UE_MAPPED, &mapping->flags);
> > +}
> > +
> > +static inline void mapping_set_mf_keep_ue_mapped(struct address_space *mapping)
> > +{
> > + set_bit(AS_MF_KEEP_UE_MAPPED, &mapping->flags);
> > +}
> > +
> > static inline gfp_t mapping_gfp_mask(const struct address_space *mapping)
> > {
> > return mapping->gfp_mask;
> > @@ -1274,6 +1286,18 @@ void replace_page_cache_folio(struct folio *old, struct folio *new);
> > void delete_from_page_cache_batch(struct address_space *mapping,
> > struct folio_batch *fbatch);
> > bool filemap_release_folio(struct folio *folio, gfp_t gfp);
> > +#ifdef CONFIG_MEMORY_FAILURE
> > +/*
> > + * Provided by memory failure to offline HWPoison-ed folio managed by memfd.
> > + */
> > +void filemap_offline_hwpoison_folio(struct address_space *mapping,
> > + struct folio *folio);
> > +#else
> > +void filemap_offline_hwpoison_folio(struct address_space *mapping,
> > + struct folio *folio)
> > +{
> > +}
> > +#endif
>
> Okay.
>
> > loff_t mapping_seek_hole_data(struct address_space *, loff_t start, loff_t end,
> > int whence);
> >
> > diff --git a/include/uapi/linux/memfd.h b/include/uapi/linux/memfd.h
> > index 273a4e15dfcff..d9875da551b7f 100644
> > --- a/include/uapi/linux/memfd.h
> > +++ b/include/uapi/linux/memfd.h
> > @@ -12,6 +12,12 @@
> > #define MFD_NOEXEC_SEAL 0x0008U
> > /* executable */
> > #define MFD_EXEC 0x0010U
> > +/*
> > + * Keep owned folios mapped when uncorrectable memory errors (UE) causes
> > + * memory failure (MF) within the folio. Only at the end of the mapping
> > + * will its HWPoison-ed folios be dealt with.
> > + */
> > +#define MFD_MF_KEEP_UE_MAPPED 0x0020U
> >
> > /*
> > * Huge page size encoding when MFD_HUGETLB is specified, and a huge page
> > diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> > index 0455119716ec0..dd3bc0b75e059 100644
> > --- a/mm/hugetlb.c
> > +++ b/mm/hugetlb.c
> > @@ -6415,6 +6415,18 @@ static bool hugetlb_pte_stable(struct hstate *h, struct mm_struct *mm, unsigned
> > return same;
> > }
> >
> > +bool hugetlb_should_keep_hwpoison_mapped(struct folio *folio,
> > + struct address_space *mapping)
> > +{
> > + if (WARN_ON_ONCE(!folio_test_hugetlb(folio)))
> > + return false;
> > +
> > + if (!mapping)
> > + return false;
> > +
> > + return mapping_mf_keep_ue_mapped(mapping);
> > +}
> > +
>
> Okay.
>
> > static vm_fault_t hugetlb_no_page(struct address_space *mapping,
> > struct vm_fault *vmf)
> > {
> > @@ -6537,9 +6549,11 @@ static vm_fault_t hugetlb_no_page(struct address_space *mapping,
> > * So we need to block hugepage fault by PG_hwpoison bit check.
> > */
> > if (unlikely(folio_test_hwpoison(folio))) {
> > - ret = VM_FAULT_HWPOISON_LARGE |
> > - VM_FAULT_SET_HINDEX(hstate_index(h));
> > - goto backout_unlocked;
> > + if (!mapping_mf_keep_ue_mapped(mapping)) {
> > + ret = VM_FAULT_HWPOISON_LARGE |
> > + VM_FAULT_SET_HINDEX(hstate_index(h));
> > + goto backout_unlocked;
> > + }
> > }
> >
>
> Looks okay, but am curious at Miaohe and others' take.
>
> To allow a known poisoned hugetlb page to be faulted in is for the sake
> of capacity, so this, versus a SIGBUS from the MF handler indicating a
> disruption and loss of both data and capacity.
> No strong opinion here, just wondering if there is any merit to limit
> the scope to the MF handler only.
>
> > /* Check for page in userfault range. */
> > diff --git a/mm/memfd.c b/mm/memfd.c
> > index 1d109c1acf211..bfdde4cf90500 100644
> > --- a/mm/memfd.c
> > +++ b/mm/memfd.c
> > @@ -313,7 +313,8 @@ long memfd_fcntl(struct file *file, unsigned int cmd, unsigned int arg)
> > #define MFD_NAME_PREFIX_LEN (sizeof(MFD_NAME_PREFIX) - 1)
> > #define MFD_NAME_MAX_LEN (NAME_MAX - MFD_NAME_PREFIX_LEN)
> >
> > -#define MFD_ALL_FLAGS (MFD_CLOEXEC | MFD_ALLOW_SEALING | MFD_HUGETLB | MFD_NOEXEC_SEAL | MFD_EXEC)
> > +#define MFD_ALL_FLAGS (MFD_CLOEXEC | MFD_ALLOW_SEALING | MFD_HUGETLB | \
> > + MFD_NOEXEC_SEAL | MFD_EXEC | MFD_MF_KEEP_UE_MAPPED)
> >
> > static int check_sysctl_memfd_noexec(unsigned int *flags)
> > {
> > @@ -387,6 +388,8 @@ static int sanitize_flags(unsigned int *flags_ptr)
> > if (!(flags & MFD_HUGETLB)) {
> > if (flags & ~MFD_ALL_FLAGS)
> > return -EINVAL;
> > + if (flags & MFD_MF_KEEP_UE_MAPPED)
> > + return -EINVAL;
> > } else {
> > /* Allow huge page size encoding in flags. */
> > if (flags & ~(MFD_ALL_FLAGS |
> > @@ -447,6 +450,16 @@ static struct file *alloc_file(const char *name, unsigned int flags)
> > file->f_mode |= FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE;
> > file->f_flags |= O_LARGEFILE;
> >
> > + /*
> > + * MFD_MF_KEEP_UE_MAPPED can only be specified in memfd_create; no API
> > + * to update it once memfd is created. MFD_MF_KEEP_UE_MAPPED is not
> > + * seal-able.
> > + *
> > + * For now MFD_MF_KEEP_UE_MAPPED is only supported by HugeTLBFS.
> > + */
> > + if (flags & (MFD_HUGETLB | MFD_MF_KEEP_UE_MAPPED))
> > + mapping_set_mf_keep_ue_mapped(file->f_mapping);
> > +
> > if (flags & MFD_NOEXEC_SEAL) {
> > struct inode *inode = file_inode(file);
> >
>
> Okay.
>
> > diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> > index 3edebb0cda30b..c5e3e28872797 100644
> > --- a/mm/memory-failure.c
> > +++ b/mm/memory-failure.c
> > @@ -373,11 +373,13 @@ static unsigned long dev_pagemap_mapping_shift(struct vm_area_struct *vma,
> > * Schedule a process for later kill.
> > * Uses GFP_ATOMIC allocations to avoid potential recursions in the VM.
> > */
> > -static void __add_to_kill(struct task_struct *tsk, const struct page *p,
> > +static void __add_to_kill(struct task_struct *tsk, struct page *p,
> > struct vm_area_struct *vma, struct list_head *to_kill,
> > unsigned long addr)
> > {
> > struct to_kill *tk;
> > + struct folio *folio;
> > + struct address_space *mapping;
> >
> > tk = kmalloc(sizeof(struct to_kill), GFP_ATOMIC);
> > if (!tk) {
> > @@ -388,8 +390,19 @@ static void __add_to_kill(struct task_struct *tsk, const struct page *p,
> > tk->addr = addr;
> > if (is_zone_device_page(p))
> > tk->size_shift = dev_pagemap_mapping_shift(vma, tk->addr);
> > - else
> > - tk->size_shift = folio_shift(page_folio(p));
> > + else {
> > + folio = page_folio(p);
> > + mapping = folio_mapping(folio);
> > + if (mapping && mapping_mf_keep_ue_mapped(mapping))
> > + /*
> > + * Let userspace know the radius of HWPoison is
> > + * the size of raw page; accessing other pages
> > + * inside the folio is still ok.
> > + */
> > + tk->size_shift = PAGE_SHIFT;
> > + else
> > + tk->size_shift = folio_shift(folio);
> > + }
> >
> > /*
> > * Send SIGKILL if "tk->addr == -EFAULT". Also, as
> > @@ -414,7 +427,7 @@ static void __add_to_kill(struct task_struct *tsk, const struct page *p,
> > list_add_tail(&tk->nd, to_kill);
> > }
> >
> > -static void add_to_kill_anon_file(struct task_struct *tsk, const struct page *p,
> > +static void add_to_kill_anon_file(struct task_struct *tsk, struct page *p,
> > struct vm_area_struct *vma, struct list_head *to_kill,
> > unsigned long addr)
> > {
> > @@ -535,7 +548,7 @@ struct task_struct *task_early_kill(struct task_struct *tsk, int force_early)
> > * Collect processes when the error hit an anonymous page.
> > */
> > static void collect_procs_anon(const struct folio *folio,
> > - const struct page *page, struct list_head *to_kill,
> > + struct page *page, struct list_head *to_kill,
> > int force_early)
> > {
> > struct task_struct *tsk;
> > @@ -573,7 +586,7 @@ static void collect_procs_anon(const struct folio *folio,
> > * Collect processes when the error hit a file mapped page.
> > */
> > static void collect_procs_file(const struct folio *folio,
> > - const struct page *page, struct list_head *to_kill,
> > + struct page *page, struct list_head *to_kill,
> > int force_early)
> > {
> > struct vm_area_struct *vma;
> > @@ -655,7 +668,7 @@ static void collect_procs_fsdax(const struct page *page,
> > /*
> > * Collect the processes who have the corrupted page mapped to kill.
> > */
> > -static void collect_procs(const struct folio *folio, const struct page *page,
> > +static void collect_procs(const struct folio *folio, struct page *page,
> > struct list_head *tokill, int force_early)
> > {
> > if (!folio->mapping)
> > @@ -1173,6 +1186,13 @@ static int me_huge_page(struct page_state *ps, struct page *p)
> > }
> > }
> >
> > + /*
> > + * MF still needs to holds a refcount for the deferred actions in
> > + * filemap_offline_hwpoison_folio.
> > + */
> > + if (hugetlb_should_keep_hwpoison_mapped(folio, mapping))
> > + return res;
> > +
>
> Okay.
>
> > if (has_extra_refcount(ps, p, extra_pins))
> > res = MF_FAILED;
> >
> > @@ -1569,6 +1589,7 @@ static bool hwpoison_user_mappings(struct folio *folio, struct page *p,
> > {
> > LIST_HEAD(tokill);
> > bool unmap_success;
> > + bool keep_mapped;
> > int forcekill;
> > bool mlocked = folio_test_mlocked(folio);
> >
> > @@ -1596,8 +1617,12 @@ static bool hwpoison_user_mappings(struct folio *folio, struct page *p,
> > */
> > collect_procs(folio, p, &tokill, flags & MF_ACTION_REQUIRED);
> >
> > - unmap_success = !unmap_poisoned_folio(folio, pfn, flags & MF_MUST_KILL);
> > - if (!unmap_success)
> > + keep_mapped = hugetlb_should_keep_hwpoison_mapped(folio, folio->mapping);
> > + if (!keep_mapped)
> > + unmap_poisoned_folio(folio, pfn, flags & MF_MUST_KILL);
> > +
> > + unmap_success = !folio_mapped(folio);
> > + if (!keep_mapped && !unmap_success)
> > pr_err("%#lx: failed to unmap page (folio mapcount=%d)\n",
> > pfn, folio_mapcount(folio));
> >
> > @@ -1622,7 +1647,7 @@ static bool hwpoison_user_mappings(struct folio *folio, struct page *p,
> > !unmap_success;
> > kill_procs(&tokill, forcekill, pfn, flags);
> >
> > - return unmap_success;
> > + return unmap_success || keep_mapped;
> > }
>
> Okay.
>
> >
> > static int identify_page_state(unsigned long pfn, struct page *p,
> > @@ -1862,6 +1887,13 @@ static unsigned long __folio_free_raw_hwp(struct folio *folio, bool move_flag)
> > unsigned long count = 0;
> >
> > head = llist_del_all(raw_hwp_list_head(folio));
> > + /*
> > + * If filemap_offline_hwpoison_folio_hugetlb is handling this folio,
> > + * it has already taken off the head of the llist.
> > + */
> > + if (head == NULL)
> > + return 0;
> > +
> > llist_for_each_entry_safe(p, next, head, node) {
> > if (move_flag)
> > SetPageHWPoison(p->page);
> > @@ -1878,7 +1910,8 @@ static int folio_set_hugetlb_hwpoison(struct folio *folio, struct page *page)
> > struct llist_head *head;
> > struct raw_hwp_page *raw_hwp;
> > struct raw_hwp_page *p;
> > - int ret = folio_test_set_hwpoison(folio) ? -EHWPOISON : 0;
> > + struct address_space *mapping = folio->mapping;
> > + bool has_hwpoison = folio_test_set_hwpoison(folio);
> >
> > /*
> > * Once the hwpoison hugepage has lost reliable raw error info,
> > @@ -1897,8 +1930,15 @@ static int folio_set_hugetlb_hwpoison(struct folio *folio, struct page *page)
> > if (raw_hwp) {
> > raw_hwp->page = page;
> > llist_add(&raw_hwp->node, head);
> > + if (hugetlb_should_keep_hwpoison_mapped(folio, mapping))
> > + /*
> > + * A new raw HWPoison page. Don't return HWPOISON.
> > + * Error event will be counted in action_result().
> > + */
> > + return 0;
> > +
> > /* the first error event will be counted in action_result(). */
> > - if (ret)
> > + if (has_hwpoison)
> > num_poisoned_pages_inc(page_to_pfn(page));
> > } else {
> > /*
> > @@ -1913,7 +1953,8 @@ static int folio_set_hugetlb_hwpoison(struct folio *folio, struct page *page)
> > */
> > __folio_free_raw_hwp(folio, false);
> > }
> > - return ret;
> > +
> > + return has_hwpoison ? -EHWPOISON : 0;
> > }
>
> Okay.
>
> >
> > static unsigned long folio_free_raw_hwp(struct folio *folio, bool move_flag)
> > @@ -2002,6 +2043,63 @@ int __get_huge_page_for_hwpoison(unsigned long pfn, int flags,
> > return ret;
> > }
> >
> > +static void filemap_offline_hwpoison_folio_hugetlb(struct folio *folio)
> > +{
> > + int ret;
> > + struct llist_node *head;
> > + struct raw_hwp_page *curr, *next;
> > + struct page *page;
> > + unsigned long pfn;
> > +
> > + /*
> > + * Since folio is still in the folio_batch, drop the refcount
> > + * elevated by filemap_get_folios.
> > + */
> > + folio_put_refs(folio, 1);
> > + head = llist_del_all(raw_hwp_list_head(folio));
> > +
> > + /*
> > + * Release refcounts held by try_memory_failure_hugetlb, one per
> > + * HWPoison-ed page in the raw hwp list.
> > + */
> > + llist_for_each_entry(curr, head, node) {
> > + SetPageHWPoison(curr->page);
> > + folio_put(folio);
> > + }
> > +
> > + /* Refcount now should be zero and ready to dissolve folio. */
> > + ret = dissolve_free_hugetlb_folio(folio);
> > + if (ret) {
> > + pr_err("failed to dissolve hugetlb folio: %d\n", ret);
> > + return;
> > + }
> > +
> > + llist_for_each_entry_safe(curr, next, head, node) {
> > + page = curr->page;
> > + pfn = page_to_pfn(page);
> > + drain_all_pages(page_zone(page));
> > + if (!take_page_off_buddy(page))
> > + pr_err("%#lx: unable to take off buddy allocator\n", pfn);
> > +
> > + page_ref_inc(page);
> > + kfree(curr);
> > + pr_info("%#lx: pending hard offline completed\n", pfn);
> > + }
> > +}
> > +
> > +void filemap_offline_hwpoison_folio(struct address_space *mapping,
> > + struct folio *folio)
> > +{
> > + WARN_ON_ONCE(!mapping);
> > +
> > + if (!folio_test_hwpoison(folio))
> > + return;
> > +
> > + /* Pending MFR currently only exist for hugetlb. */
> > + if (hugetlb_should_keep_hwpoison_mapped(folio, mapping))
> > + filemap_offline_hwpoison_folio_hugetlb(folio);
> > +}
> > +
> > /*
> > * Taking refcount of hugetlb pages needs extra care about race conditions
> > * with basic operations like hugepage allocation/free/demotion.
>
>
> Looks good.
>
> thanks,
> -jane
Sorry, resending for the non-HTML version.
--
Hello Jiaqi,
Here is a summary of a few nits in this code:
- Some functions declarations are problematic according to me
- The parameter testing to activate the feature looks incorrect
- The function signature change is probably not necessary
- Maybe we should wait for an agreement on your other proposal:
[PATCH v1 0/2] Only free healthy pages in high-order HWPoison folio
The last item is not a nit, but as your above proposal may require to
keep all data of a
hugetlb folio to recycle it correctly (especially the list of poisoned
sub-pages), and
to avoid the race condition with returning poisoned pages to the
freelist right before
removing them; you may need to change some aspects of this current code.
On 11/16/25 02:32, Jiaqi Yan wrote:
> [...]
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index 8e63e46b8e1f0..b7733ef5ee917 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -871,10 +871,17 @@ int dissolve_free_hugetlb_folios(unsigned long start_pfn,
>
> #ifdef CONFIG_MEMORY_FAILURE
> extern void folio_clear_hugetlb_hwpoison(struct folio *folio);
> +extern bool hugetlb_should_keep_hwpoison_mapped(struct folio *folio,
> + struct address_space *mapping);
> #else
> static inline void folio_clear_hugetlb_hwpoison(struct folio *folio)
> {
> }
> +static inline bool hugetlb_should_keep_hwpoison_mapped(struct folio *folio
> + struct address_space *mapping)
> +{
> + return false;
> +}
> #endif
You are conditionally declaring this
hugetlb_should_keep_hwpoison_mapped() function and implementing
it into mm/hugetlb.c, but this file can be compiled in both cases
(CONFIG_MEMORY_FAILURE enabled or not)
So you either need to have a single consistent declaration with the
implementation and use something like that:
bool hugetlb_should_keep_hwpoison_mapped(struct folio *folio,
struct address_space *mapping)
{
+#ifdef CONFIG_MEMORY_FAILURE
if (WARN_ON_ONCE(!folio_test_hugetlb(folio)))
return false;
@@ -6087,6 +6088,9 @@ bool hugetlb_should_keep_hwpoison_mapped(struct
folio *folio,
return false;
return mapping_mf_keep_ue_mapped(mapping);
+#else
+ return false;
+#endif
}
Or keep your double declaration and hide the implementation when
CONFIG_MEMORY_FAILURE is enabled:
+#ifdef CONFIG_MEMORY_FAILURE
bool hugetlb_should_keep_hwpoison_mapped(struct folio *folio,
struct address_space *mapping)
{
if (WARN_ON_ONCE(!folio_test_hugetlb(folio)))
return false;
@@ -6087,6 +6088,9 @@ bool hugetlb_should_keep_hwpoison_mapped(struct
folio *folio,
return false;
return mapping_mf_keep_ue_mapped(mapping);
}
+#endif
>
> #ifdef CONFIG_ARCH_ENABLE_HUGEPAGE_MIGRATION
> diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
> index 09b581c1d878d..9ad511aacde7c 100644
> --- a/include/linux/pagemap.h
> +++ b/include/linux/pagemap.h
> @@ -213,6 +213,8 @@ enum mapping_flags {
> AS_WRITEBACK_MAY_DEADLOCK_ON_RECLAIM = 9,
> AS_KERNEL_FILE = 10, /* mapping for a fake kernel file that shouldn't
> account usage to user cgroups */
> + /* For MFD_MF_KEEP_UE_MAPPED. */
> + AS_MF_KEEP_UE_MAPPED = 11,
> /* Bits 16-25 are used for FOLIO_ORDER */
> AS_FOLIO_ORDER_BITS = 5,
> AS_FOLIO_ORDER_MIN = 16,
> @@ -348,6 +350,16 @@ static inline bool mapping_writeback_may_deadlock_on_reclaim(const struct addres
> return test_bit(AS_WRITEBACK_MAY_DEADLOCK_ON_RECLAIM, &mapping->flags);
> }
>
> +static inline bool mapping_mf_keep_ue_mapped(const struct address_space *mapping)
> +{
> + return test_bit(AS_MF_KEEP_UE_MAPPED, &mapping->flags);
> +}
> +
> +static inline void mapping_set_mf_keep_ue_mapped(struct address_space *mapping)
> +{
> + set_bit(AS_MF_KEEP_UE_MAPPED, &mapping->flags);
> +}
> +
> static inline gfp_t mapping_gfp_mask(const struct address_space *mapping)
> {
> return mapping->gfp_mask;
> @@ -1274,6 +1286,18 @@ void replace_page_cache_folio(struct folio *old, struct folio *new);
> void delete_from_page_cache_batch(struct address_space *mapping,
> struct folio_batch *fbatch);
> bool filemap_release_folio(struct folio *folio, gfp_t gfp);
> +#ifdef CONFIG_MEMORY_FAILURE
> +/*
> + * Provided by memory failure to offline HWPoison-ed folio managed by memfd.
> + */
> +void filemap_offline_hwpoison_folio(struct address_space *mapping,
> + struct folio *folio);
> +#else
> +void filemap_offline_hwpoison_folio(struct address_space *mapping,
> + struct folio *folio)
> +{
> +}
> +#endif
> loff_t mapping_seek_hole_data(struct address_space *, loff_t start, loff_t end,
> int whence);
>
This filemap_offline_hwpoison_folio() declaration also is problematic in
the case without
CONFIG_MEMORY_FAILURE, as we implement a public function
filemap_offline_hwpoison_folio()
in all the files including this "pagemap.h" header.
This coud be solved using "static inline" in this second case.
> diff --git a/mm/memfd.c b/mm/memfd.c
> index 1d109c1acf211..bfdde4cf90500 100644
> --- a/mm/memfd.c
> +++ b/mm/memfd.c
> @@ -313,7 +313,8 @@ long memfd_fcntl(struct file *file, unsigned int cmd, unsigned int arg)
> #define MFD_NAME_PREFIX_LEN (sizeof(MFD_NAME_PREFIX) - 1)
> #define MFD_NAME_MAX_LEN (NAME_MAX - MFD_NAME_PREFIX_LEN)
>
> -#define MFD_ALL_FLAGS (MFD_CLOEXEC | MFD_ALLOW_SEALING | MFD_HUGETLB | MFD_NOEXEC_SEAL | MFD_EXEC)
> +#define MFD_ALL_FLAGS (MFD_CLOEXEC | MFD_ALLOW_SEALING | MFD_HUGETLB | \
> + MFD_NOEXEC_SEAL | MFD_EXEC | MFD_MF_KEEP_UE_MAPPED)
>
> static int check_sysctl_memfd_noexec(unsigned int *flags)
> {
> @@ -387,6 +388,8 @@ static int sanitize_flags(unsigned int *flags_ptr)
> if (!(flags & MFD_HUGETLB)) {
> if (flags & ~MFD_ALL_FLAGS)
> return -EINVAL;
> + if (flags & MFD_MF_KEEP_UE_MAPPED)
> + return -EINVAL;
> } else {
> /* Allow huge page size encoding in flags. */
> if (flags & ~(MFD_ALL_FLAGS |
> @@ -447,6 +450,16 @@ static struct file *alloc_file(const char *name, unsigned int flags)
> file->f_mode |= FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE;
> file->f_flags |= O_LARGEFILE;
>
> + /*
> + * MFD_MF_KEEP_UE_MAPPED can only be specified in memfd_create; no API
> + * to update it once memfd is created. MFD_MF_KEEP_UE_MAPPED is not
> + * seal-able.
> + *
> + * For now MFD_MF_KEEP_UE_MAPPED is only supported by HugeTLBFS.
> + */
> + if (flags & (MFD_HUGETLB | MFD_MF_KEEP_UE_MAPPED))
> + mapping_set_mf_keep_ue_mapped(file->f_mapping);
> +
The flags value that we need to have in order to set the "keep" value on
the address space
is MFD_MF_KEEP_UE_MAPPED alone, as we already verified that the value is
only given combined
to MFD_HUGETLB.
This is a nit identified by Harry Yoo during our internal conversations.
Thanks Harry !
> if (flags & MFD_NOEXEC_SEAL) {
> struct inode *inode = file_inode(file);
>
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 3edebb0cda30b..c5e3e28872797 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -373,11 +373,13 @@ static unsigned long dev_pagemap_mapping_shift(struct vm_area_struct *vma,
> * Schedule a process for later kill.
> * Uses GFP_ATOMIC allocations to avoid potential recursions in the VM.
> */
> -static void __add_to_kill(struct task_struct *tsk, const struct page *p,
> +static void __add_to_kill(struct task_struct *tsk, struct page *p,
> struct vm_area_struct *vma, struct list_head *to_kill,
> unsigned long addr)
Is there any reason to remove the "const" on the page structure in the
signature ?
It looks like you only do that for the new call to page_folio(p), but we
don't touch the page
> {
> struct to_kill *tk;
> + struct folio *folio;
You could use a "const" struct folio *folio too.
> + struct address_space *mapping;
>
> tk = kmalloc(sizeof(struct to_kill), GFP_ATOMIC);
> if (!tk) {
> @@ -388,8 +390,19 @@ static void __add_to_kill(struct task_struct *tsk, const struct page *p,
> tk->addr = addr;
> if (is_zone_device_page(p))
> tk->size_shift = dev_pagemap_mapping_shift(vma, tk->addr);
> - else
> - tk->size_shift = folio_shift(page_folio(p));
> + else {
> + folio = page_folio(p);
Now with both folio and p being "const", the code should work.
> + mapping = folio_mapping(folio);
> + if (mapping && mapping_mf_keep_ue_mapped(mapping))
> + /*
> + * Let userspace know the radius of HWPoison is
> + * the size of raw page; accessing other pages
> + * inside the folio is still ok.
> + */
> + tk->size_shift = PAGE_SHIFT;
> + else
> + tk->size_shift = folio_shift(folio);
> + }
>
> /*
> * Send SIGKILL if "tk->addr == -EFAULT". Also, as
> @@ -414,7 +427,7 @@ static void __add_to_kill(struct task_struct *tsk, const struct page *p,
> list_add_tail(&tk->nd, to_kill);
> }
>
> -static void add_to_kill_anon_file(struct task_struct *tsk, const struct page *p,
> +static void add_to_kill_anon_file(struct task_struct *tsk, struct page *p,
No need to change the signature here too (otherwise you would have
missed both functions
add_to_kill_fsdax() and add_to_kill_ksm().
> struct vm_area_struct *vma, struct list_head *to_kill,
> unsigned long addr)
> {
> @@ -535,7 +548,7 @@ struct task_struct *task_early_kill(struct task_struct *tsk, int force_early)
> * Collect processes when the error hit an anonymous page.
> */
> static void collect_procs_anon(const struct folio *folio,
> - const struct page *page, struct list_head *to_kill,
> + struct page *page, struct list_head *to_kill,
No need to change
> int force_early)
> {
> struct task_struct *tsk;
> @@ -573,7 +586,7 @@ static void collect_procs_anon(const struct folio *folio,
> * Collect processes when the error hit a file mapped page.
> */
> static void collect_procs_file(const struct folio *folio,
> - const struct page *page, struct list_head *to_kill,
> + struct page *page, struct list_head *to_kill,
> int force_early)
No need to change
> {
> struct vm_area_struct *vma;
> @@ -655,7 +668,7 @@ static void collect_procs_fsdax(const struct page *page,
> /*
> * Collect the processes who have the corrupted page mapped to kill.
> */
> -static void collect_procs(const struct folio *folio, const struct page *page,
> +static void collect_procs(const struct folio *folio, struct page *page,
> struct list_head *tokill, int force_early)
> {
> if (!folio->mapping)
> @@ -1173,6 +1186,13 @@ static int me_huge_page(struct page_state *ps, struct page *p)
> }
> }
>
> + /*
> + * MF still needs to holds a refcount for the deferred actions in
> + * filemap_offline_hwpoison_folio.
> + */
> + if (hugetlb_should_keep_hwpoison_mapped(folio, mapping))
> + return res;
> +
> if (has_extra_refcount(ps, p, extra_pins))
> res = MF_FAILED;
>
> @@ -1569,6 +1589,7 @@ static bool hwpoison_user_mappings(struct folio *folio, struct page *p,
> {
> LIST_HEAD(tokill);
> bool unmap_success;
> + bool keep_mapped;
> int forcekill;
> bool mlocked = folio_test_mlocked(folio);
>
> @@ -1596,8 +1617,12 @@ static bool hwpoison_user_mappings(struct folio *folio, struct page *p,
> */
> collect_procs(folio, p, &tokill, flags & MF_ACTION_REQUIRED);
>
> - unmap_success = !unmap_poisoned_folio(folio, pfn, flags & MF_MUST_KILL);
> - if (!unmap_success)
> + keep_mapped = hugetlb_should_keep_hwpoison_mapped(folio, folio->mapping);
> + if (!keep_mapped)
> + unmap_poisoned_folio(folio, pfn, flags & MF_MUST_KILL);
> +
> + unmap_success = !folio_mapped(folio);
> + if (!keep_mapped && !unmap_success)
> pr_err("%#lx: failed to unmap page (folio mapcount=%d)\n",
> pfn, folio_mapcount(folio));
>
> @@ -1622,7 +1647,7 @@ static bool hwpoison_user_mappings(struct folio *folio, struct page *p,
> !unmap_success;
> kill_procs(&tokill, forcekill, pfn, flags);
>
> - return unmap_success;
> + return unmap_success || keep_mapped;
> }
>
> static int identify_page_state(unsigned long pfn, struct page *p,
> @@ -1862,6 +1887,13 @@ static unsigned long __folio_free_raw_hwp(struct folio *folio, bool move_flag)
> unsigned long count = 0;
>
> head = llist_del_all(raw_hwp_list_head(folio));
> + /*
> + * If filemap_offline_hwpoison_folio_hugetlb is handling this folio,
> + * it has already taken off the head of the llist.
> + */
> + if (head == NULL)
> + return 0;
> +
This may not be necessary depending on how we recycle hugetlb pages --
see below too.
> llist_for_each_entry_safe(p, next, head, node) {
> if (move_flag)
> SetPageHWPoison(p->page);
> @@ -1878,7 +1910,8 @@ static int folio_set_hugetlb_hwpoison(struct folio *folio, struct page *page)
> struct llist_head *head;
> struct raw_hwp_page *raw_hwp;
> struct raw_hwp_page *p;
> - int ret = folio_test_set_hwpoison(folio) ? -EHWPOISON : 0;
> + struct address_space *mapping = folio->mapping;
> + bool has_hwpoison = folio_test_set_hwpoison(folio);
>
> /*
> * Once the hwpoison hugepage has lost reliable raw error info,
> @@ -1897,8 +1930,15 @@ static int folio_set_hugetlb_hwpoison(struct folio *folio, struct page *page)
> if (raw_hwp) {
> raw_hwp->page = page;
> llist_add(&raw_hwp->node, head);
> + if (hugetlb_should_keep_hwpoison_mapped(folio, mapping))
> + /*
> + * A new raw HWPoison page. Don't return HWPOISON.
> + * Error event will be counted in action_result().
> + */
> + return 0;
> +
> /* the first error event will be counted in action_result(). */
> - if (ret)
> + if (has_hwpoison)
> num_poisoned_pages_inc(page_to_pfn(page));
> } else {
> /*
> @@ -1913,7 +1953,8 @@ static int folio_set_hugetlb_hwpoison(struct folio *folio, struct page *page)
> */
> __folio_free_raw_hwp(folio, false);
> }
> - return ret;
> +
> + return has_hwpoison ? -EHWPOISON : 0;
> }
>
> static unsigned long folio_free_raw_hwp(struct folio *folio, bool move_flag)
> @@ -2002,6 +2043,63 @@ int __get_huge_page_for_hwpoison(unsigned long pfn, int flags,
> return ret;
> }
>
> +static void filemap_offline_hwpoison_folio_hugetlb(struct folio *folio)
> +{
> + int ret;
> + struct llist_node *head;
> + struct raw_hwp_page *curr, *next;
> + struct page *page;
> + unsigned long pfn;
> +
> + /*
> + * Since folio is still in the folio_batch, drop the refcount
> + * elevated by filemap_get_folios.
> + */
> + folio_put_refs(folio, 1);
> + head = llist_del_all(raw_hwp_list_head(folio));
According to me we should wait until your other patch set is approved to
decide if the folio raw_hwp_list
has to be removed from the folio or if is should be left there so that
the recycling of this huge page
works correctly...
> +
> + /*
> + * Release refcounts held by try_memory_failure_hugetlb, one per
> + * HWPoison-ed page in the raw hwp list.
> + */
> + llist_for_each_entry(curr, head, node) {
> + SetPageHWPoison(curr->page);
> + folio_put(folio);
> + }
> +
> + /* Refcount now should be zero and ready to dissolve folio. */
> + ret = dissolve_free_hugetlb_folio(folio);
> + if (ret) {
> + pr_err("failed to dissolve hugetlb folio: %d\n", ret);
> + return;
> + }
> +
> + llist_for_each_entry_safe(curr, next, head, node) {
> + page = curr->page;
> + pfn = page_to_pfn(page);
> + drain_all_pages(page_zone(page));
> + if (!take_page_off_buddy(page))
> + pr_err("%#lx: unable to take off buddy allocator\n", pfn);
> +
> + page_ref_inc(page);
> + kfree(curr);
> + pr_info("%#lx: pending hard offline completed\n", pfn);
> + }
> +}
Let's revisit this above function when an agreement is reached on the
recycling hugetlb pages proposal.
> +
> +void filemap_offline_hwpoison_folio(struct address_space *mapping,
> + struct folio *folio)
> +{
> + WARN_ON_ONCE(!mapping);
> +
> + if (!folio_test_hwpoison(folio))
> + return;
> +
> + /* Pending MFR currently only exist for hugetlb. */
> + if (hugetlb_should_keep_hwpoison_mapped(folio, mapping))
> + filemap_offline_hwpoison_folio_hugetlb(folio);
> +}
> +
> /*
> * Taking refcount of hugetlb pages needs extra care about race conditions
> * with basic operations like hugepage allocation/free/demotion.
HTH
Best regards,
William.
Hi William,
Thanks for your reviews, I should be able to address your comments in v3.
On Tue, Nov 25, 2025 at 2:04 PM William Roche <william.roche@oracle.com> wrote:
>
> Sorry, resending for the non-HTML version.
> --
>
> Hello Jiaqi,
>
> Here is a summary of a few nits in this code:
>
> - Some functions declarations are problematic according to me
> - The parameter testing to activate the feature looks incorrect
> - The function signature change is probably not necessary
> - Maybe we should wait for an agreement on your other proposal:
> [PATCH v1 0/2] Only free healthy pages in high-order HWPoison folio
>
> The last item is not a nit, but as your above proposal may require to
> keep all data of a
> hugetlb folio to recycle it correctly (especially the list of poisoned
> sub-pages), and
> to avoid the race condition with returning poisoned pages to the
> freelist right before
> removing them; you may need to change some aspects of this current code.
>
>
>
>
> On 11/16/25 02:32, Jiaqi Yan wrote:
> > [...]
> > diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> > index 8e63e46b8e1f0..b7733ef5ee917 100644
> > --- a/include/linux/hugetlb.h
> > +++ b/include/linux/hugetlb.h
> > @@ -871,10 +871,17 @@ int dissolve_free_hugetlb_folios(unsigned long start_pfn,
> >
> > #ifdef CONFIG_MEMORY_FAILURE
> > extern void folio_clear_hugetlb_hwpoison(struct folio *folio);
> > +extern bool hugetlb_should_keep_hwpoison_mapped(struct folio *folio,
> > + struct address_space *mapping);
> > #else
> > static inline void folio_clear_hugetlb_hwpoison(struct folio *folio)
> > {
> > }
> > +static inline bool hugetlb_should_keep_hwpoison_mapped(struct folio *folio
> > + struct address_space *mapping)
> > +{
> > + return false;
> > +}
> > #endif
>
> You are conditionally declaring this
> hugetlb_should_keep_hwpoison_mapped() function and implementing
> it into mm/hugetlb.c, but this file can be compiled in both cases
> (CONFIG_MEMORY_FAILURE enabled or not)
> So you either need to have a single consistent declaration with the
> implementation and use something like that:
>
> bool hugetlb_should_keep_hwpoison_mapped(struct folio *folio,
> struct address_space *mapping)
> {
> +#ifdef CONFIG_MEMORY_FAILURE
> if (WARN_ON_ONCE(!folio_test_hugetlb(folio)))
> return false;
>
> @@ -6087,6 +6088,9 @@ bool hugetlb_should_keep_hwpoison_mapped(struct
> folio *folio,
> return false;
>
> return mapping_mf_keep_ue_mapped(mapping);
> +#else
> + return false;
> +#endif
> }
>
> Or keep your double declaration and hide the implementation when
> CONFIG_MEMORY_FAILURE is enabled:
>
> +#ifdef CONFIG_MEMORY_FAILURE
> bool hugetlb_should_keep_hwpoison_mapped(struct folio *folio,
> struct address_space *mapping)
> {
> if (WARN_ON_ONCE(!folio_test_hugetlb(folio)))
> return false;
>
> @@ -6087,6 +6088,9 @@ bool hugetlb_should_keep_hwpoison_mapped(struct
> folio *folio,
> return false;
>
> return mapping_mf_keep_ue_mapped(mapping);
> }
> +#endif
>
Thanks for your suggestions! I think probably I can move the real
hugetlb_should_keep_hwpoison_mapped() implementation to
memory_failure.c, similar to how folio_clear_hugetlb_hwpoison() is
implemented.
>
>
> >
> > #ifdef CONFIG_ARCH_ENABLE_HUGEPAGE_MIGRATION
> > diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
> > index 09b581c1d878d..9ad511aacde7c 100644
> > --- a/include/linux/pagemap.h
> > +++ b/include/linux/pagemap.h
> > @@ -213,6 +213,8 @@ enum mapping_flags {
> > AS_WRITEBACK_MAY_DEADLOCK_ON_RECLAIM = 9,
> > AS_KERNEL_FILE = 10, /* mapping for a fake kernel file that shouldn't
> > account usage to user cgroups */
> > + /* For MFD_MF_KEEP_UE_MAPPED. */
> > + AS_MF_KEEP_UE_MAPPED = 11,
> > /* Bits 16-25 are used for FOLIO_ORDER */
> > AS_FOLIO_ORDER_BITS = 5,
> > AS_FOLIO_ORDER_MIN = 16,
> > @@ -348,6 +350,16 @@ static inline bool mapping_writeback_may_deadlock_on_reclaim(const struct addres
> > return test_bit(AS_WRITEBACK_MAY_DEADLOCK_ON_RECLAIM, &mapping->flags);
> > }
> >
> > +static inline bool mapping_mf_keep_ue_mapped(const struct address_space *mapping)
> > +{
> > + return test_bit(AS_MF_KEEP_UE_MAPPED, &mapping->flags);
> > +}
> > +
> > +static inline void mapping_set_mf_keep_ue_mapped(struct address_space *mapping)
> > +{
> > + set_bit(AS_MF_KEEP_UE_MAPPED, &mapping->flags);
> > +}
> > +
> > static inline gfp_t mapping_gfp_mask(const struct address_space *mapping)
> > {
> > return mapping->gfp_mask;
> > @@ -1274,6 +1286,18 @@ void replace_page_cache_folio(struct folio *old, struct folio *new);
> > void delete_from_page_cache_batch(struct address_space *mapping,
> > struct folio_batch *fbatch);
> > bool filemap_release_folio(struct folio *folio, gfp_t gfp);
> > +#ifdef CONFIG_MEMORY_FAILURE
> > +/*
> > + * Provided by memory failure to offline HWPoison-ed folio managed by memfd.
> > + */
> > +void filemap_offline_hwpoison_folio(struct address_space *mapping,
> > + struct folio *folio);
> > +#else
> > +void filemap_offline_hwpoison_folio(struct address_space *mapping,
> > + struct folio *folio)
> > +{
> > +}
> > +#endif
> > loff_t mapping_seek_hole_data(struct address_space *, loff_t start, loff_t end,
> > int whence);
> >
>
> This filemap_offline_hwpoison_folio() declaration also is problematic in
> the case without
> CONFIG_MEMORY_FAILURE, as we implement a public function
> filemap_offline_hwpoison_folio()
> in all the files including this "pagemap.h" header.
>
> This coud be solved using "static inline" in this second case.
Yep, will do in v3.
>
>
>
> > diff --git a/mm/memfd.c b/mm/memfd.c
> > index 1d109c1acf211..bfdde4cf90500 100644
> > --- a/mm/memfd.c
> > +++ b/mm/memfd.c
> > @@ -313,7 +313,8 @@ long memfd_fcntl(struct file *file, unsigned int cmd, unsigned int arg)
> > #define MFD_NAME_PREFIX_LEN (sizeof(MFD_NAME_PREFIX) - 1)
> > #define MFD_NAME_MAX_LEN (NAME_MAX - MFD_NAME_PREFIX_LEN)
> >
> > -#define MFD_ALL_FLAGS (MFD_CLOEXEC | MFD_ALLOW_SEALING | MFD_HUGETLB | MFD_NOEXEC_SEAL | MFD_EXEC)
> > +#define MFD_ALL_FLAGS (MFD_CLOEXEC | MFD_ALLOW_SEALING | MFD_HUGETLB | \
> > + MFD_NOEXEC_SEAL | MFD_EXEC | MFD_MF_KEEP_UE_MAPPED)
> >
> > static int check_sysctl_memfd_noexec(unsigned int *flags)
> > {
> > @@ -387,6 +388,8 @@ static int sanitize_flags(unsigned int *flags_ptr)
> > if (!(flags & MFD_HUGETLB)) {
> > if (flags & ~MFD_ALL_FLAGS)
> > return -EINVAL;
> > + if (flags & MFD_MF_KEEP_UE_MAPPED)
> > + return -EINVAL;
> > } else {
> > /* Allow huge page size encoding in flags. */
> > if (flags & ~(MFD_ALL_FLAGS |
> > @@ -447,6 +450,16 @@ static struct file *alloc_file(const char *name, unsigned int flags)
> > file->f_mode |= FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE;
> > file->f_flags |= O_LARGEFILE;
> >
> > + /*
> > + * MFD_MF_KEEP_UE_MAPPED can only be specified in memfd_create; no API
> > + * to update it once memfd is created. MFD_MF_KEEP_UE_MAPPED is not
> > + * seal-able.
> > + *
> > + * For now MFD_MF_KEEP_UE_MAPPED is only supported by HugeTLBFS.
> > + */
> > + if (flags & (MFD_HUGETLB | MFD_MF_KEEP_UE_MAPPED))
> > + mapping_set_mf_keep_ue_mapped(file->f_mapping);
> > +
>
> The flags value that we need to have in order to set the "keep" value on
> the address space
> is MFD_MF_KEEP_UE_MAPPED alone, as we already verified that the value is
> only given combined
> to MFD_HUGETLB.
> This is a nit identified by Harry Yoo during our internal conversations.
> Thanks Harry !
Yeah, this is redundant to sanitize_flags(). Will simplify in v3.
>
>
> > if (flags & MFD_NOEXEC_SEAL) {
> > struct inode *inode = file_inode(file);
> >
> > diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> > index 3edebb0cda30b..c5e3e28872797 100644
> > --- a/mm/memory-failure.c
> > +++ b/mm/memory-failure.c
> > @@ -373,11 +373,13 @@ static unsigned long dev_pagemap_mapping_shift(struct vm_area_struct *vma,
> > * Schedule a process for later kill.
> > * Uses GFP_ATOMIC allocations to avoid potential recursions in the VM.
> > */
> > -static void __add_to_kill(struct task_struct *tsk, const struct page *p,
> > +static void __add_to_kill(struct task_struct *tsk, struct page *p,
> > struct vm_area_struct *vma, struct list_head *to_kill,
> > unsigned long addr)
>
> Is there any reason to remove the "const" on the page structure in the
> signature ?
> It looks like you only do that for the new call to page_folio(p), but we
> don't touch the page
>
>
> > {
> > struct to_kill *tk;
> > + struct folio *folio;
>
> You could use a "const" struct folio *folio too.
Yes, will revert the changes to "const" all over the places.
>
>
>
> > + struct address_space *mapping;
> >
> > tk = kmalloc(sizeof(struct to_kill), GFP_ATOMIC);
> > if (!tk) {
> > @@ -388,8 +390,19 @@ static void __add_to_kill(struct task_struct *tsk, const struct page *p,
> > tk->addr = addr;
> > if (is_zone_device_page(p))
> > tk->size_shift = dev_pagemap_mapping_shift(vma, tk->addr);
> > - else
> > - tk->size_shift = folio_shift(page_folio(p));
> > + else {
> > + folio = page_folio(p);
>
> Now with both folio and p being "const", the code should work.
>
>
>
> > + mapping = folio_mapping(folio);
> > + if (mapping && mapping_mf_keep_ue_mapped(mapping))
> > + /*
> > + * Let userspace know the radius of HWPoison is
> > + * the size of raw page; accessing other pages
> > + * inside the folio is still ok.
> > + */
> > + tk->size_shift = PAGE_SHIFT;
> > + else
> > + tk->size_shift = folio_shift(folio);
> > + }
> >
> > /*
> > * Send SIGKILL if "tk->addr == -EFAULT". Also, as
> > @@ -414,7 +427,7 @@ static void __add_to_kill(struct task_struct *tsk, const struct page *p,
> > list_add_tail(&tk->nd, to_kill);
> > }
> >
> > -static void add_to_kill_anon_file(struct task_struct *tsk, const struct page *p,
> > +static void add_to_kill_anon_file(struct task_struct *tsk, struct page *p,
>
> No need to change the signature here too (otherwise you would have
> missed both functions
> add_to_kill_fsdax() and add_to_kill_ksm().
>
>
> > struct vm_area_struct *vma, struct list_head *to_kill,
> > unsigned long addr)
> > {
> > @@ -535,7 +548,7 @@ struct task_struct *task_early_kill(struct task_struct *tsk, int force_early)
> > * Collect processes when the error hit an anonymous page.
> > */
> > static void collect_procs_anon(const struct folio *folio,
> > - const struct page *page, struct list_head *to_kill,
> > + struct page *page, struct list_head *to_kill,
>
> No need to change
>
>
> > int force_early)
> > {
> > struct task_struct *tsk;
> > @@ -573,7 +586,7 @@ static void collect_procs_anon(const struct folio *folio,
> > * Collect processes when the error hit a file mapped page.
> > */
> > static void collect_procs_file(const struct folio *folio,
> > - const struct page *page, struct list_head *to_kill,
> > + struct page *page, struct list_head *to_kill,
> > int force_early)
>
> No need to change
>
> > {
> > struct vm_area_struct *vma;
> > @@ -655,7 +668,7 @@ static void collect_procs_fsdax(const struct page *page,
> > /*
> > * Collect the processes who have the corrupted page mapped to kill.
> > */
> > -static void collect_procs(const struct folio *folio, const struct page *page,
> > +static void collect_procs(const struct folio *folio, struct page *page,
> > struct list_head *tokill, int force_early)
> > {
> > if (!folio->mapping)
> > @@ -1173,6 +1186,13 @@ static int me_huge_page(struct page_state *ps, struct page *p)
> > }
> > }
> >
> > + /*
> > + * MF still needs to holds a refcount for the deferred actions in
> > + * filemap_offline_hwpoison_folio.
> > + */
> > + if (hugetlb_should_keep_hwpoison_mapped(folio, mapping))
> > + return res;
> > +
> > if (has_extra_refcount(ps, p, extra_pins))
> > res = MF_FAILED;
> >
> > @@ -1569,6 +1589,7 @@ static bool hwpoison_user_mappings(struct folio *folio, struct page *p,
> > {
> > LIST_HEAD(tokill);
> > bool unmap_success;
> > + bool keep_mapped;
> > int forcekill;
> > bool mlocked = folio_test_mlocked(folio);
> >
> > @@ -1596,8 +1617,12 @@ static bool hwpoison_user_mappings(struct folio *folio, struct page *p,
> > */
> > collect_procs(folio, p, &tokill, flags & MF_ACTION_REQUIRED);
> >
> > - unmap_success = !unmap_poisoned_folio(folio, pfn, flags & MF_MUST_KILL);
> > - if (!unmap_success)
> > + keep_mapped = hugetlb_should_keep_hwpoison_mapped(folio, folio->mapping);
> > + if (!keep_mapped)
> > + unmap_poisoned_folio(folio, pfn, flags & MF_MUST_KILL);
> > +
> > + unmap_success = !folio_mapped(folio);
> > + if (!keep_mapped && !unmap_success)
> > pr_err("%#lx: failed to unmap page (folio mapcount=%d)\n",
> > pfn, folio_mapcount(folio));
> >
> > @@ -1622,7 +1647,7 @@ static bool hwpoison_user_mappings(struct folio *folio, struct page *p,
> > !unmap_success;
> > kill_procs(&tokill, forcekill, pfn, flags);
> >
> > - return unmap_success;
> > + return unmap_success || keep_mapped;
> > }
> >
> > static int identify_page_state(unsigned long pfn, struct page *p,
> > @@ -1862,6 +1887,13 @@ static unsigned long __folio_free_raw_hwp(struct folio *folio, bool move_flag)
> > unsigned long count = 0;
> >
> > head = llist_del_all(raw_hwp_list_head(folio));
> > + /*
> > + * If filemap_offline_hwpoison_folio_hugetlb is handling this folio,
> > + * it has already taken off the head of the llist.
> > + */
> > + if (head == NULL)
> > + return 0;
> > +
>
> This may not be necessary depending on how we recycle hugetlb pages --
> see below too.
>
> > llist_for_each_entry_safe(p, next, head, node) {
> > if (move_flag)
> > SetPageHWPoison(p->page);
> > @@ -1878,7 +1910,8 @@ static int folio_set_hugetlb_hwpoison(struct folio *folio, struct page *page)
> > struct llist_head *head;
> > struct raw_hwp_page *raw_hwp;
> > struct raw_hwp_page *p;
> > - int ret = folio_test_set_hwpoison(folio) ? -EHWPOISON : 0;
> > + struct address_space *mapping = folio->mapping;
> > + bool has_hwpoison = folio_test_set_hwpoison(folio);
> >
> > /*
> > * Once the hwpoison hugepage has lost reliable raw error info,
> > @@ -1897,8 +1930,15 @@ static int folio_set_hugetlb_hwpoison(struct folio *folio, struct page *page)
> > if (raw_hwp) {
> > raw_hwp->page = page;
> > llist_add(&raw_hwp->node, head);
> > + if (hugetlb_should_keep_hwpoison_mapped(folio, mapping))
> > + /*
> > + * A new raw HWPoison page. Don't return HWPOISON.
> > + * Error event will be counted in action_result().
> > + */
> > + return 0;
> > +
> > /* the first error event will be counted in action_result(). */
> > - if (ret)
> > + if (has_hwpoison)
> > num_poisoned_pages_inc(page_to_pfn(page));
> > } else {
> > /*
> > @@ -1913,7 +1953,8 @@ static int folio_set_hugetlb_hwpoison(struct folio *folio, struct page *page)
> > */
> > __folio_free_raw_hwp(folio, false);
> > }
> > - return ret;
> > +
> > + return has_hwpoison ? -EHWPOISON : 0;
> > }
> >
> > static unsigned long folio_free_raw_hwp(struct folio *folio, bool move_flag)
> > @@ -2002,6 +2043,63 @@ int __get_huge_page_for_hwpoison(unsigned long pfn, int flags,
> > return ret;
> > }
> >
> > +static void filemap_offline_hwpoison_folio_hugetlb(struct folio *folio)
> > +{
> > + int ret;
> > + struct llist_node *head;
> > + struct raw_hwp_page *curr, *next;
> > + struct page *page;
> > + unsigned long pfn;
> > +
> > + /*
> > + * Since folio is still in the folio_batch, drop the refcount
> > + * elevated by filemap_get_folios.
> > + */
> > + folio_put_refs(folio, 1);
> > + head = llist_del_all(raw_hwp_list_head(folio));
>
> According to me we should wait until your other patch set is approved to
> decide if the folio raw_hwp_list
> has to be removed from the folio or if is should be left there so that
> the recycling of this huge page
> works correctly...
>
> > +
> > + /*
> > + * Release refcounts held by try_memory_failure_hugetlb, one per
> > + * HWPoison-ed page in the raw hwp list.
> > + */
> > + llist_for_each_entry(curr, head, node) {
> > + SetPageHWPoison(curr->page);
> > + folio_put(folio);
> > + }
> > +
> > + /* Refcount now should be zero and ready to dissolve folio. */
> > + ret = dissolve_free_hugetlb_folio(folio);
> > + if (ret) {
> > + pr_err("failed to dissolve hugetlb folio: %d\n", ret);
> > + return;
> > + }
> > +
> > + llist_for_each_entry_safe(curr, next, head, node) {
> > + page = curr->page;
> > + pfn = page_to_pfn(page);
> > + drain_all_pages(page_zone(page));
> > + if (!take_page_off_buddy(page))
> > + pr_err("%#lx: unable to take off buddy allocator\n", pfn);
> > +
> > + page_ref_inc(page);
> > + kfree(curr);
> > + pr_info("%#lx: pending hard offline completed\n", pfn);
> > + }
> > +}
>
> Let's revisit this above function when an agreement is reached on the
> recycling hugetlb pages proposal.
From what I can tell, free_has_hwpoisoned() is promising. So in v3 I
will post much simplified filemap_offline_hwpoison_folio_hugetlb(),
assuming dissolve_free_hugetlb_folio() recycles only the healthy
pages.
>
>
>
>
>
> > +
> > +void filemap_offline_hwpoison_folio(struct address_space *mapping,
> > + struct folio *folio)
> > +{
> > + WARN_ON_ONCE(!mapping);
> > +
> > + if (!folio_test_hwpoison(folio))
> > + return;
> > +
> > + /* Pending MFR currently only exist for hugetlb. */
> > + if (hugetlb_should_keep_hwpoison_mapped(folio, mapping))
> > + filemap_offline_hwpoison_folio_hugetlb(folio);
> > +}
> > +
> > /*
> > * Taking refcount of hugetlb pages needs extra care about race conditions
> > * with basic operations like hugepage allocation/free/demotion.
>
>
> HTH
>
> Best regards,
> William.
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