This patch completely moves the old userfaultfd core to use the new
vm_uffd_ops API. After this change, existing file systems will start to
use the new API for userfault operations.
When at it, moving vma_can_userfault() into mm/userfaultfd.c instead,
because it's getting too big. It's only used in slow paths so it shouldn't
be an issue.
This will also remove quite some hard-coded checks for either shmem or
hugetlbfs. Now all the old checks should still work but with vm_uffd_ops.
Note that anonymous memory will still need to be processed separately
because it doesn't have vm_ops at all.
Signed-off-by: Peter Xu <peterx@redhat.com>
---
include/linux/shmem_fs.h | 14 -----
include/linux/userfaultfd_k.h | 46 ++++----------
mm/shmem.c | 2 +-
mm/userfaultfd.c | 115 +++++++++++++++++++++++++---------
4 files changed, 101 insertions(+), 76 deletions(-)
diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h
index 6d0f9c599ff7..2f5b7b295cf6 100644
--- a/include/linux/shmem_fs.h
+++ b/include/linux/shmem_fs.h
@@ -195,20 +195,6 @@ static inline pgoff_t shmem_fallocend(struct inode *inode, pgoff_t eof)
extern bool shmem_charge(struct inode *inode, long pages);
extern void shmem_uncharge(struct inode *inode, long pages);
-#ifdef CONFIG_USERFAULTFD
-#ifdef CONFIG_SHMEM
-extern int shmem_mfill_atomic_pte(pmd_t *dst_pmd,
- struct vm_area_struct *dst_vma,
- unsigned long dst_addr,
- unsigned long src_addr,
- uffd_flags_t flags,
- struct folio **foliop);
-#else /* !CONFIG_SHMEM */
-#define shmem_mfill_atomic_pte(dst_pmd, dst_vma, dst_addr, \
- src_addr, flags, foliop) ({ BUG(); 0; })
-#endif /* CONFIG_SHMEM */
-#endif /* CONFIG_USERFAULTFD */
-
/*
* Used space is stored as unsigned 64-bit value in bytes but
* quota core supports only signed 64-bit values so use that
diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h
index e79c724b3b95..4e56ad423a4a 100644
--- a/include/linux/userfaultfd_k.h
+++ b/include/linux/userfaultfd_k.h
@@ -85,9 +85,14 @@ extern vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason);
#define MFILL_ATOMIC_FLAG(nr) ((__force uffd_flags_t) MFILL_ATOMIC_BIT(nr))
#define MFILL_ATOMIC_MODE_MASK ((__force uffd_flags_t) (MFILL_ATOMIC_BIT(0) - 1))
+static inline enum mfill_atomic_mode uffd_flags_get_mode(uffd_flags_t flags)
+{
+ return (enum mfill_atomic_mode)(flags & MFILL_ATOMIC_MODE_MASK);
+}
+
static inline bool uffd_flags_mode_is(uffd_flags_t flags, enum mfill_atomic_mode expected)
{
- return (flags & MFILL_ATOMIC_MODE_MASK) == ((__force uffd_flags_t) expected);
+ return uffd_flags_get_mode(flags) == expected;
}
static inline uffd_flags_t uffd_flags_set_mode(uffd_flags_t flags, enum mfill_atomic_mode mode)
@@ -196,41 +201,16 @@ static inline bool userfaultfd_armed(struct vm_area_struct *vma)
return vma->vm_flags & __VM_UFFD_FLAGS;
}
-static inline bool vma_can_userfault(struct vm_area_struct *vma,
- unsigned long vm_flags,
- bool wp_async)
+static inline const vm_uffd_ops *vma_get_uffd_ops(struct vm_area_struct *vma)
{
- vm_flags &= __VM_UFFD_FLAGS;
-
- if (vma->vm_flags & VM_DROPPABLE)
- return false;
-
- if ((vm_flags & VM_UFFD_MINOR) &&
- (!is_vm_hugetlb_page(vma) && !vma_is_shmem(vma)))
- return false;
-
- /*
- * If wp async enabled, and WP is the only mode enabled, allow any
- * memory type.
- */
- if (wp_async && (vm_flags == VM_UFFD_WP))
- return true;
-
-#ifndef CONFIG_PTE_MARKER_UFFD_WP
- /*
- * If user requested uffd-wp but not enabled pte markers for
- * uffd-wp, then shmem & hugetlbfs are not supported but only
- * anonymous.
- */
- if ((vm_flags & VM_UFFD_WP) && !vma_is_anonymous(vma))
- return false;
-#endif
-
- /* By default, allow any of anon|shmem|hugetlb */
- return vma_is_anonymous(vma) || is_vm_hugetlb_page(vma) ||
- vma_is_shmem(vma);
+ if (vma->vm_ops && vma->vm_ops->userfaultfd_ops)
+ return vma->vm_ops->userfaultfd_ops;
+ return NULL;
}
+bool vma_can_userfault(struct vm_area_struct *vma,
+ unsigned long vm_flags, bool wp_async);
+
static inline bool vma_has_uffd_without_event_remap(struct vm_area_struct *vma)
{
struct userfaultfd_ctx *uffd_ctx = vma->vm_userfaultfd_ctx.ctx;
diff --git a/mm/shmem.c b/mm/shmem.c
index bd0a29000318..4d71fc7be358 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -3158,7 +3158,7 @@ static int shmem_uffd_get_folio(struct inode *inode, pgoff_t pgoff,
return shmem_get_folio(inode, pgoff, 0, folio, SGP_NOALLOC);
}
-int shmem_mfill_atomic_pte(pmd_t *dst_pmd,
+static int shmem_mfill_atomic_pte(pmd_t *dst_pmd,
struct vm_area_struct *dst_vma,
unsigned long dst_addr,
unsigned long src_addr,
diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index 879505c6996f..61783ff2d335 100644
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -14,12 +14,48 @@
#include <linux/userfaultfd_k.h>
#include <linux/mmu_notifier.h>
#include <linux/hugetlb.h>
-#include <linux/shmem_fs.h>
#include <asm/tlbflush.h>
#include <asm/tlb.h>
#include "internal.h"
#include "swap.h"
+bool vma_can_userfault(struct vm_area_struct *vma,
+ unsigned long vm_flags, bool wp_async)
+{
+ unsigned long supported;
+
+ if (vma->vm_flags & VM_DROPPABLE)
+ return false;
+
+ vm_flags &= __VM_UFFD_FLAGS;
+
+#ifndef CONFIG_PTE_MARKER_UFFD_WP
+ /*
+ * If user requested uffd-wp but not enabled pte markers for
+ * uffd-wp, then any file system (like shmem or hugetlbfs) are not
+ * supported but only anonymous.
+ */
+ if ((vm_flags & VM_UFFD_WP) && !vma_is_anonymous(vma))
+ return false;
+#endif
+ /*
+ * If wp async enabled, and WP is the only mode enabled, allow any
+ * memory type.
+ */
+ if (wp_async && (vm_flags == VM_UFFD_WP))
+ return true;
+
+ if (vma_is_anonymous(vma))
+ /* Anonymous has no page cache, MINOR not supported */
+ supported = VM_UFFD_MISSING | VM_UFFD_WP;
+ else if (vma_get_uffd_ops(vma))
+ supported = vma_get_uffd_ops(vma)->uffd_features;
+ else
+ return false;
+
+ return !(vm_flags & (~supported));
+}
+
static __always_inline
bool validate_dst_vma(struct vm_area_struct *dst_vma, unsigned long dst_end)
{
@@ -384,11 +420,15 @@ static int mfill_atomic_pte_continue(pmd_t *dst_pmd,
{
struct inode *inode = file_inode(dst_vma->vm_file);
pgoff_t pgoff = linear_page_index(dst_vma, dst_addr);
+ const vm_uffd_ops *uffd_ops = vma_get_uffd_ops(dst_vma);
struct folio *folio;
struct page *page;
int ret;
- ret = shmem_get_folio(inode, pgoff, 0, &folio, SGP_NOALLOC);
+ if (WARN_ON_ONCE(!uffd_ops || !uffd_ops->uffd_get_folio))
+ return -EINVAL;
+
+ ret = uffd_ops->uffd_get_folio(inode, pgoff, &folio);
/* Our caller expects us to return -EFAULT if we failed to find folio */
if (ret == -ENOENT)
ret = -EFAULT;
@@ -504,18 +544,6 @@ static __always_inline ssize_t mfill_atomic_hugetlb(
u32 hash;
struct address_space *mapping;
- /*
- * There is no default zero huge page for all huge page sizes as
- * supported by hugetlb. A PMD_SIZE huge pages may exist as used
- * by THP. Since we can not reliably insert a zero page, this
- * feature is not supported.
- */
- if (uffd_flags_mode_is(flags, MFILL_ATOMIC_ZEROPAGE)) {
- up_read(&ctx->map_changing_lock);
- uffd_mfill_unlock(dst_vma);
- return -EINVAL;
- }
-
src_addr = src_start;
dst_addr = dst_start;
copied = 0;
@@ -686,14 +714,55 @@ static __always_inline ssize_t mfill_atomic_pte(pmd_t *dst_pmd,
err = mfill_atomic_pte_zeropage(dst_pmd,
dst_vma, dst_addr);
} else {
- err = shmem_mfill_atomic_pte(dst_pmd, dst_vma,
- dst_addr, src_addr,
- flags, foliop);
+ const vm_uffd_ops *uffd_ops = vma_get_uffd_ops(dst_vma);
+
+ if (WARN_ON_ONCE(!uffd_ops || !uffd_ops->uffd_copy)) {
+ err = -EINVAL;
+ } else {
+ err = uffd_ops->uffd_copy(dst_pmd, dst_vma,
+ dst_addr, src_addr,
+ flags, foliop);
+ }
}
return err;
}
+static inline bool
+vma_uffd_ops_supported(struct vm_area_struct *vma, uffd_flags_t flags)
+{
+ enum mfill_atomic_mode mode = uffd_flags_get_mode(flags);
+ const vm_uffd_ops *uffd_ops;
+ unsigned long uffd_ioctls;
+
+ if ((flags & MFILL_ATOMIC_WP) && !(vma->vm_flags & VM_UFFD_WP))
+ return false;
+
+ /* Anonymous supports everything except CONTINUE */
+ if (vma_is_anonymous(vma))
+ return mode != MFILL_ATOMIC_CONTINUE;
+
+ uffd_ops = vma_get_uffd_ops(vma);
+ if (!uffd_ops)
+ return false;
+
+ uffd_ioctls = uffd_ops->uffd_ioctls;
+ switch (mode) {
+ case MFILL_ATOMIC_COPY:
+ return uffd_ioctls & BIT(_UFFDIO_COPY);
+ case MFILL_ATOMIC_ZEROPAGE:
+ return uffd_ioctls & BIT(_UFFDIO_ZEROPAGE);
+ case MFILL_ATOMIC_CONTINUE:
+ if (!(vma->vm_flags & VM_SHARED))
+ return false;
+ return uffd_ioctls & BIT(_UFFDIO_CONTINUE);
+ case MFILL_ATOMIC_POISON:
+ return uffd_ioctls & BIT(_UFFDIO_POISON);
+ default:
+ return false;
+ }
+}
+
static __always_inline ssize_t mfill_atomic(struct userfaultfd_ctx *ctx,
unsigned long dst_start,
unsigned long src_start,
@@ -752,11 +821,7 @@ static __always_inline ssize_t mfill_atomic(struct userfaultfd_ctx *ctx,
dst_vma->vm_flags & VM_SHARED))
goto out_unlock;
- /*
- * validate 'mode' now that we know the dst_vma: don't allow
- * a wrprotect copy if the userfaultfd didn't register as WP.
- */
- if ((flags & MFILL_ATOMIC_WP) && !(dst_vma->vm_flags & VM_UFFD_WP))
+ if (!vma_uffd_ops_supported(dst_vma, flags))
goto out_unlock;
/*
@@ -766,12 +831,6 @@ static __always_inline ssize_t mfill_atomic(struct userfaultfd_ctx *ctx,
return mfill_atomic_hugetlb(ctx, dst_vma, dst_start,
src_start, len, flags);
- if (!vma_is_anonymous(dst_vma) && !vma_is_shmem(dst_vma))
- goto out_unlock;
- if (!vma_is_shmem(dst_vma) &&
- uffd_flags_mode_is(flags, MFILL_ATOMIC_CONTINUE))
- goto out_unlock;
-
while (src_addr < src_start + len) {
pmd_t dst_pmdval;
--
2.49.0On Fri, Jun 20, 2025 at 12:04 PM Peter Xu <peterx@redhat.com> wrote:
>
> This patch completely moves the old userfaultfd core to use the new
> vm_uffd_ops API. After this change, existing file systems will start to
> use the new API for userfault operations.
>
> When at it, moving vma_can_userfault() into mm/userfaultfd.c instead,
> because it's getting too big. It's only used in slow paths so it shouldn't
> be an issue.
>
> This will also remove quite some hard-coded checks for either shmem or
> hugetlbfs. Now all the old checks should still work but with vm_uffd_ops.
>
> Note that anonymous memory will still need to be processed separately
> because it doesn't have vm_ops at all.
>
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
> include/linux/shmem_fs.h | 14 -----
> include/linux/userfaultfd_k.h | 46 ++++----------
> mm/shmem.c | 2 +-
> mm/userfaultfd.c | 115 +++++++++++++++++++++++++---------
> 4 files changed, 101 insertions(+), 76 deletions(-)
>
> diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h
> index 6d0f9c599ff7..2f5b7b295cf6 100644
> --- a/include/linux/shmem_fs.h
> +++ b/include/linux/shmem_fs.h
> @@ -195,20 +195,6 @@ static inline pgoff_t shmem_fallocend(struct inode *inode, pgoff_t eof)
> extern bool shmem_charge(struct inode *inode, long pages);
> extern void shmem_uncharge(struct inode *inode, long pages);
>
> -#ifdef CONFIG_USERFAULTFD
> -#ifdef CONFIG_SHMEM
> -extern int shmem_mfill_atomic_pte(pmd_t *dst_pmd,
> - struct vm_area_struct *dst_vma,
> - unsigned long dst_addr,
> - unsigned long src_addr,
> - uffd_flags_t flags,
> - struct folio **foliop);
> -#else /* !CONFIG_SHMEM */
> -#define shmem_mfill_atomic_pte(dst_pmd, dst_vma, dst_addr, \
> - src_addr, flags, foliop) ({ BUG(); 0; })
> -#endif /* CONFIG_SHMEM */
> -#endif /* CONFIG_USERFAULTFD */
> -
> /*
> * Used space is stored as unsigned 64-bit value in bytes but
> * quota core supports only signed 64-bit values so use that
> diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h
> index e79c724b3b95..4e56ad423a4a 100644
> --- a/include/linux/userfaultfd_k.h
> +++ b/include/linux/userfaultfd_k.h
> @@ -85,9 +85,14 @@ extern vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason);
> #define MFILL_ATOMIC_FLAG(nr) ((__force uffd_flags_t) MFILL_ATOMIC_BIT(nr))
> #define MFILL_ATOMIC_MODE_MASK ((__force uffd_flags_t) (MFILL_ATOMIC_BIT(0) - 1))
>
> +static inline enum mfill_atomic_mode uffd_flags_get_mode(uffd_flags_t flags)
> +{
> + return (enum mfill_atomic_mode)(flags & MFILL_ATOMIC_MODE_MASK);
> +}
> +
> static inline bool uffd_flags_mode_is(uffd_flags_t flags, enum mfill_atomic_mode expected)
> {
> - return (flags & MFILL_ATOMIC_MODE_MASK) == ((__force uffd_flags_t) expected);
> + return uffd_flags_get_mode(flags) == expected;
> }
>
> static inline uffd_flags_t uffd_flags_set_mode(uffd_flags_t flags, enum mfill_atomic_mode mode)
> @@ -196,41 +201,16 @@ static inline bool userfaultfd_armed(struct vm_area_struct *vma)
> return vma->vm_flags & __VM_UFFD_FLAGS;
> }
>
> -static inline bool vma_can_userfault(struct vm_area_struct *vma,
> - unsigned long vm_flags,
> - bool wp_async)
> +static inline const vm_uffd_ops *vma_get_uffd_ops(struct vm_area_struct *vma)
> {
> - vm_flags &= __VM_UFFD_FLAGS;
> -
> - if (vma->vm_flags & VM_DROPPABLE)
> - return false;
> -
> - if ((vm_flags & VM_UFFD_MINOR) &&
> - (!is_vm_hugetlb_page(vma) && !vma_is_shmem(vma)))
> - return false;
> -
> - /*
> - * If wp async enabled, and WP is the only mode enabled, allow any
> - * memory type.
> - */
> - if (wp_async && (vm_flags == VM_UFFD_WP))
> - return true;
> -
> -#ifndef CONFIG_PTE_MARKER_UFFD_WP
> - /*
> - * If user requested uffd-wp but not enabled pte markers for
> - * uffd-wp, then shmem & hugetlbfs are not supported but only
> - * anonymous.
> - */
> - if ((vm_flags & VM_UFFD_WP) && !vma_is_anonymous(vma))
> - return false;
> -#endif
Hi Peter,
Thanks for this cleanup!
It looks like the above two checks, the wp-async one and the PTE
marker check, have been reordered in this patch. Does this result in a
functional difference?
The rest of this series looks fine to me. :)
> -
> - /* By default, allow any of anon|shmem|hugetlb */
> - return vma_is_anonymous(vma) || is_vm_hugetlb_page(vma) ||
> - vma_is_shmem(vma);
> + if (vma->vm_ops && vma->vm_ops->userfaultfd_ops)
> + return vma->vm_ops->userfaultfd_ops;
> + return NULL;
> }
>
> +bool vma_can_userfault(struct vm_area_struct *vma,
> + unsigned long vm_flags, bool wp_async);
> +
> static inline bool vma_has_uffd_without_event_remap(struct vm_area_struct *vma)
> {
> struct userfaultfd_ctx *uffd_ctx = vma->vm_userfaultfd_ctx.ctx;
> diff --git a/mm/shmem.c b/mm/shmem.c
> index bd0a29000318..4d71fc7be358 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -3158,7 +3158,7 @@ static int shmem_uffd_get_folio(struct inode *inode, pgoff_t pgoff,
> return shmem_get_folio(inode, pgoff, 0, folio, SGP_NOALLOC);
> }
>
> -int shmem_mfill_atomic_pte(pmd_t *dst_pmd,
> +static int shmem_mfill_atomic_pte(pmd_t *dst_pmd,
> struct vm_area_struct *dst_vma,
> unsigned long dst_addr,
> unsigned long src_addr,
> diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
> index 879505c6996f..61783ff2d335 100644
> --- a/mm/userfaultfd.c
> +++ b/mm/userfaultfd.c
> @@ -14,12 +14,48 @@
> #include <linux/userfaultfd_k.h>
> #include <linux/mmu_notifier.h>
> #include <linux/hugetlb.h>
> -#include <linux/shmem_fs.h>
> #include <asm/tlbflush.h>
> #include <asm/tlb.h>
> #include "internal.h"
> #include "swap.h"
>
> +bool vma_can_userfault(struct vm_area_struct *vma,
> + unsigned long vm_flags, bool wp_async)
> +{
> + unsigned long supported;
> +
> + if (vma->vm_flags & VM_DROPPABLE)
> + return false;
> +
> + vm_flags &= __VM_UFFD_FLAGS;
> +
> +#ifndef CONFIG_PTE_MARKER_UFFD_WP
> + /*
> + * If user requested uffd-wp but not enabled pte markers for
> + * uffd-wp, then any file system (like shmem or hugetlbfs) are not
> + * supported but only anonymous.
> + */
> + if ((vm_flags & VM_UFFD_WP) && !vma_is_anonymous(vma))
> + return false;
> +#endif
> + /*
> + * If wp async enabled, and WP is the only mode enabled, allow any
> + * memory type.
> + */
> + if (wp_async && (vm_flags == VM_UFFD_WP))
> + return true;
> +
> + if (vma_is_anonymous(vma))
> + /* Anonymous has no page cache, MINOR not supported */
> + supported = VM_UFFD_MISSING | VM_UFFD_WP;
> + else if (vma_get_uffd_ops(vma))
> + supported = vma_get_uffd_ops(vma)->uffd_features;
> + else
> + return false;
> +
> + return !(vm_flags & (~supported));
> +}
> +
> static __always_inline
> bool validate_dst_vma(struct vm_area_struct *dst_vma, unsigned long dst_end)
> {
> @@ -384,11 +420,15 @@ static int mfill_atomic_pte_continue(pmd_t *dst_pmd,
> {
> struct inode *inode = file_inode(dst_vma->vm_file);
> pgoff_t pgoff = linear_page_index(dst_vma, dst_addr);
> + const vm_uffd_ops *uffd_ops = vma_get_uffd_ops(dst_vma);
> struct folio *folio;
> struct page *page;
> int ret;
>
> - ret = shmem_get_folio(inode, pgoff, 0, &folio, SGP_NOALLOC);
> + if (WARN_ON_ONCE(!uffd_ops || !uffd_ops->uffd_get_folio))
> + return -EINVAL;
> +
> + ret = uffd_ops->uffd_get_folio(inode, pgoff, &folio);
> /* Our caller expects us to return -EFAULT if we failed to find folio */
> if (ret == -ENOENT)
> ret = -EFAULT;
> @@ -504,18 +544,6 @@ static __always_inline ssize_t mfill_atomic_hugetlb(
> u32 hash;
> struct address_space *mapping;
>
> - /*
> - * There is no default zero huge page for all huge page sizes as
> - * supported by hugetlb. A PMD_SIZE huge pages may exist as used
> - * by THP. Since we can not reliably insert a zero page, this
> - * feature is not supported.
> - */
> - if (uffd_flags_mode_is(flags, MFILL_ATOMIC_ZEROPAGE)) {
> - up_read(&ctx->map_changing_lock);
> - uffd_mfill_unlock(dst_vma);
> - return -EINVAL;
> - }
> -
> src_addr = src_start;
> dst_addr = dst_start;
> copied = 0;
> @@ -686,14 +714,55 @@ static __always_inline ssize_t mfill_atomic_pte(pmd_t *dst_pmd,
> err = mfill_atomic_pte_zeropage(dst_pmd,
> dst_vma, dst_addr);
> } else {
> - err = shmem_mfill_atomic_pte(dst_pmd, dst_vma,
> - dst_addr, src_addr,
> - flags, foliop);
> + const vm_uffd_ops *uffd_ops = vma_get_uffd_ops(dst_vma);
> +
> + if (WARN_ON_ONCE(!uffd_ops || !uffd_ops->uffd_copy)) {
> + err = -EINVAL;
> + } else {
> + err = uffd_ops->uffd_copy(dst_pmd, dst_vma,
> + dst_addr, src_addr,
> + flags, foliop);
> + }
> }
>
> return err;
> }
>
> +static inline bool
> +vma_uffd_ops_supported(struct vm_area_struct *vma, uffd_flags_t flags)
> +{
> + enum mfill_atomic_mode mode = uffd_flags_get_mode(flags);
> + const vm_uffd_ops *uffd_ops;
> + unsigned long uffd_ioctls;
> +
> + if ((flags & MFILL_ATOMIC_WP) && !(vma->vm_flags & VM_UFFD_WP))
> + return false;
> +
> + /* Anonymous supports everything except CONTINUE */
> + if (vma_is_anonymous(vma))
> + return mode != MFILL_ATOMIC_CONTINUE;
> +
> + uffd_ops = vma_get_uffd_ops(vma);
> + if (!uffd_ops)
> + return false;
> +
> + uffd_ioctls = uffd_ops->uffd_ioctls;
> + switch (mode) {
> + case MFILL_ATOMIC_COPY:
> + return uffd_ioctls & BIT(_UFFDIO_COPY);
> + case MFILL_ATOMIC_ZEROPAGE:
> + return uffd_ioctls & BIT(_UFFDIO_ZEROPAGE);
> + case MFILL_ATOMIC_CONTINUE:
> + if (!(vma->vm_flags & VM_SHARED))
> + return false;
> + return uffd_ioctls & BIT(_UFFDIO_CONTINUE);
> + case MFILL_ATOMIC_POISON:
> + return uffd_ioctls & BIT(_UFFDIO_POISON);
> + default:
> + return false;
> + }
> +}
> +
> static __always_inline ssize_t mfill_atomic(struct userfaultfd_ctx *ctx,
> unsigned long dst_start,
> unsigned long src_start,
> @@ -752,11 +821,7 @@ static __always_inline ssize_t mfill_atomic(struct userfaultfd_ctx *ctx,
> dst_vma->vm_flags & VM_SHARED))
> goto out_unlock;
>
> - /*
> - * validate 'mode' now that we know the dst_vma: don't allow
> - * a wrprotect copy if the userfaultfd didn't register as WP.
> - */
> - if ((flags & MFILL_ATOMIC_WP) && !(dst_vma->vm_flags & VM_UFFD_WP))
> + if (!vma_uffd_ops_supported(dst_vma, flags))
> goto out_unlock;
>
> /*
> @@ -766,12 +831,6 @@ static __always_inline ssize_t mfill_atomic(struct userfaultfd_ctx *ctx,
> return mfill_atomic_hugetlb(ctx, dst_vma, dst_start,
> src_start, len, flags);
>
> - if (!vma_is_anonymous(dst_vma) && !vma_is_shmem(dst_vma))
> - goto out_unlock;
> - if (!vma_is_shmem(dst_vma) &&
> - uffd_flags_mode_is(flags, MFILL_ATOMIC_CONTINUE))
> - goto out_unlock;
> -
> while (src_addr < src_start + len) {
> pmd_t dst_pmdval;
>
> --
> 2.49.0
>
On Wed, Jun 25, 2025 at 01:31:49PM -0700, James Houghton wrote:
> > -static inline bool vma_can_userfault(struct vm_area_struct *vma,
> > - unsigned long vm_flags,
> > - bool wp_async)
> > +static inline const vm_uffd_ops *vma_get_uffd_ops(struct vm_area_struct *vma)
> > {
> > - vm_flags &= __VM_UFFD_FLAGS;
> > -
> > - if (vma->vm_flags & VM_DROPPABLE)
> > - return false;
> > -
> > - if ((vm_flags & VM_UFFD_MINOR) &&
> > - (!is_vm_hugetlb_page(vma) && !vma_is_shmem(vma)))
> > - return false;
> > -
> > - /*
> > - * If wp async enabled, and WP is the only mode enabled, allow any
> > - * memory type.
> > - */
> > - if (wp_async && (vm_flags == VM_UFFD_WP))
> > - return true;
> > -
> > -#ifndef CONFIG_PTE_MARKER_UFFD_WP
> > - /*
> > - * If user requested uffd-wp but not enabled pte markers for
> > - * uffd-wp, then shmem & hugetlbfs are not supported but only
> > - * anonymous.
> > - */
> > - if ((vm_flags & VM_UFFD_WP) && !vma_is_anonymous(vma))
> > - return false;
> > -#endif
>
> Hi Peter,
>
> Thanks for this cleanup!
>
> It looks like the above two checks, the wp-async one and the PTE
> marker check, have been reordered in this patch. Does this result in a
> functional difference?
>
> The rest of this series looks fine to me. :)
Thanks for the very careful review, James!
Yes that's a small tweak I did when moving. I don't expect to have any
functional change. Maybe I should at least mention that in the commit log.
Here I did the movement because fundamentally wp_async depends on the pte
markers, so it may be slightly more intuitive to check pte markers first,
rejecting any form of file wr-protect traps. Otherwise it may looks like
we could return the true for wp_async==true too early. In reality IIUC it
can't happen.
For example, currently userfaultfd_api() has:
#ifndef CONFIG_PTE_MARKER_UFFD_WP
uffdio_api.features &= ~UFFD_FEATURE_WP_HUGETLBFS_SHMEM;
uffdio_api.features &= ~UFFD_FEATURE_WP_UNPOPULATED;
uffdio_api.features &= ~UFFD_FEATURE_WP_ASYNC;
#endif
So when wp_async can be true above, pte markers must be compiled.. IOW,
above code clip should work identically with below lines:
#ifdef CONFIG_PTE_MARKER_UFFD_WP
if (wp_async && (vm_flags == VM_UFFD_WP))
return true;
#endif
#ifndef CONFIG_PTE_MARKER_UFFD_WP
if ((vm_flags & VM_UFFD_WP) && !vma_is_anonymous(vma))
return false;
#endif
Then it means both chunks of code cannot be compiled together. The order
shouldn't matter.
But maybe I should just move it back as before, to save the explain and
confusions. Let me know if you have any preference.
Thanks,
--
Peter Xu
On Wed, Jun 25, 2025 at 2:21 PM Peter Xu <peterx@redhat.com> wrote:
>
> On Wed, Jun 25, 2025 at 01:31:49PM -0700, James Houghton wrote:
> > > -static inline bool vma_can_userfault(struct vm_area_struct *vma,
> > > - unsigned long vm_flags,
> > > - bool wp_async)
> > > +static inline const vm_uffd_ops *vma_get_uffd_ops(struct vm_area_struct *vma)
> > > {
> > > - vm_flags &= __VM_UFFD_FLAGS;
> > > -
> > > - if (vma->vm_flags & VM_DROPPABLE)
> > > - return false;
> > > -
> > > - if ((vm_flags & VM_UFFD_MINOR) &&
> > > - (!is_vm_hugetlb_page(vma) && !vma_is_shmem(vma)))
> > > - return false;
> > > -
> > > - /*
> > > - * If wp async enabled, and WP is the only mode enabled, allow any
> > > - * memory type.
> > > - */
> > > - if (wp_async && (vm_flags == VM_UFFD_WP))
> > > - return true;
> > > -
> > > -#ifndef CONFIG_PTE_MARKER_UFFD_WP
> > > - /*
> > > - * If user requested uffd-wp but not enabled pte markers for
> > > - * uffd-wp, then shmem & hugetlbfs are not supported but only
> > > - * anonymous.
> > > - */
> > > - if ((vm_flags & VM_UFFD_WP) && !vma_is_anonymous(vma))
> > > - return false;
> > > -#endif
> >
> > Hi Peter,
> >
> > Thanks for this cleanup!
> >
> > It looks like the above two checks, the wp-async one and the PTE
> > marker check, have been reordered in this patch. Does this result in a
> > functional difference?
> >
> > The rest of this series looks fine to me. :)
>
> Thanks for the very careful review, James!
>
> Yes that's a small tweak I did when moving. I don't expect to have any
> functional change. Maybe I should at least mention that in the commit log.
Yeah if you could leave a small explanation, like what you have below,
in the commit log, that would be good. :)
>
> Here I did the movement because fundamentally wp_async depends on the pte
> markers, so it may be slightly more intuitive to check pte markers first,
> rejecting any form of file wr-protect traps. Otherwise it may looks like
> we could return the true for wp_async==true too early. In reality IIUC it
> can't happen.
>
> For example, currently userfaultfd_api() has:
>
> #ifndef CONFIG_PTE_MARKER_UFFD_WP
> uffdio_api.features &= ~UFFD_FEATURE_WP_HUGETLBFS_SHMEM;
> uffdio_api.features &= ~UFFD_FEATURE_WP_UNPOPULATED;
> uffdio_api.features &= ~UFFD_FEATURE_WP_ASYNC;
> #endif
Ah, I see, thanks!
> So when wp_async can be true above, pte markers must be compiled.. IOW,
> above code clip should work identically with below lines:
>
> #ifdef CONFIG_PTE_MARKER_UFFD_WP
> if (wp_async && (vm_flags == VM_UFFD_WP))
> return true;
> #endif
>
> #ifndef CONFIG_PTE_MARKER_UFFD_WP
> if ((vm_flags & VM_UFFD_WP) && !vma_is_anonymous(vma))
> return false;
> #endif
>
> Then it means both chunks of code cannot be compiled together. The order
> shouldn't matter.
>
> But maybe I should just move it back as before, to save the explain and
> confusions. Let me know if you have any preference.
Feel free to leave this patch as it is, that's fine. Thanks for the
explanation. :)
If you'd like, feel free to add:
Reviewed-by: James Houghton <jthoughton@google.com>
Hi Peter,
kernel test robot noticed the following build warnings:
[auto build test WARNING on next-20250620]
[cannot apply to akpm-mm/mm-everything linus/master v6.16-rc2 v6.16-rc1 v6.15 v6.16-rc2]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Peter-Xu/mm-Introduce-vm_uffd_ops-API/20250621-030557
base: next-20250620
patch link: https://lore.kernel.org/r/20250620190342.1780170-5-peterx%40redhat.com
patch subject: [PATCH 4/4] mm: Apply vm_uffd_ops API to core mm
config: i386-randconfig-061-20250622 (https://download.01.org/0day-ci/archive/20250623/202506230216.JVgQj2Si-lkp@intel.com/config)
compiler: gcc-11 (Debian 11.3.0-12) 11.3.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250623/202506230216.JVgQj2Si-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202506230216.JVgQj2Si-lkp@intel.com/
sparse warnings: (new ones prefixed by >>)
mm/shmem.c: note: in included file (through include/linux/shmem_fs.h):
>> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
--
mm/hugetlb.c:669:12: sparse: sparse: context imbalance in 'allocate_file_region_entries' - wrong count at exit
mm/hugetlb.c:740:13: sparse: sparse: context imbalance in 'region_add' - wrong count at exit
mm/hugetlb.c:807:13: sparse: sparse: context imbalance in 'region_chg' - wrong count at exit
mm/hugetlb.c:5798:20: sparse: sparse: context imbalance in 'move_huge_pte' - different lock contexts for basic block
mm/hugetlb.c: note: in included file:
include/linux/mm.h:1391:22: sparse: sparse: context imbalance in 'hugetlb_wp' - unexpected unlock
mm/hugetlb.c: note: in included file (through include/linux/hugetlb.h, include/linux/migrate.h):
>> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
>> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
--
mm/userfaultfd.c:270:9: sparse: sparse: context imbalance in 'mfill_atomic_install_pte' - different lock contexts for basic block
mm/userfaultfd.c:412:9: sparse: sparse: context imbalance in 'mfill_atomic_pte_zeropage' - different lock contexts for basic block
mm/userfaultfd.c:498:9: sparse: sparse: context imbalance in 'mfill_atomic_pte_poison' - different lock contexts for basic block
mm/userfaultfd.c: note: in included file:
>> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
>> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
>> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
>> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
>> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
>> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
>> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
>> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
>> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
>> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
>> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
>> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
>> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
>> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
>> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
>> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
>> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
>> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
>> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
>> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
mm/userfaultfd.c: note: in included file (through include/linux/rbtree.h, include/linux/mm_types.h, include/linux/mmzone.h, ...):
include/linux/rcupdate.h:871:25: sparse: sparse: context imbalance in 'move_pages_pte' - unexpected unlock
vim +90 include/linux/userfaultfd_k.h
87
88 static inline enum mfill_atomic_mode uffd_flags_get_mode(uffd_flags_t flags)
89 {
> 90 return (enum mfill_atomic_mode)(flags & MFILL_ATOMIC_MODE_MASK);
91 }
92
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
On Mon, Jun 23, 2025 at 03:09:13AM +0800, kernel test robot wrote:
> Hi Peter,
>
> kernel test robot noticed the following build warnings:
>
> [auto build test WARNING on next-20250620]
> [cannot apply to akpm-mm/mm-everything linus/master v6.16-rc2 v6.16-rc1 v6.15 v6.16-rc2]
> [If your patch is applied to the wrong git tree, kindly drop us a note.
> And when submitting patch, we suggest to use '--base' as documented in
> https://git-scm.com/docs/git-format-patch#_base_tree_information]
>
> url: https://github.com/intel-lab-lkp/linux/commits/Peter-Xu/mm-Introduce-vm_uffd_ops-API/20250621-030557
> base: next-20250620
> patch link: https://lore.kernel.org/r/20250620190342.1780170-5-peterx%40redhat.com
> patch subject: [PATCH 4/4] mm: Apply vm_uffd_ops API to core mm
> config: i386-randconfig-061-20250622 (https://download.01.org/0day-ci/archive/20250623/202506230216.JVgQj2Si-lkp@intel.com/config)
> compiler: gcc-11 (Debian 11.3.0-12) 11.3.0
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250623/202506230216.JVgQj2Si-lkp@intel.com/reproduce)
>
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202506230216.JVgQj2Si-lkp@intel.com/
>
> sparse warnings: (new ones prefixed by >>)
> mm/shmem.c: note: in included file (through include/linux/shmem_fs.h):
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> --
> mm/hugetlb.c:669:12: sparse: sparse: context imbalance in 'allocate_file_region_entries' - wrong count at exit
> mm/hugetlb.c:740:13: sparse: sparse: context imbalance in 'region_add' - wrong count at exit
> mm/hugetlb.c:807:13: sparse: sparse: context imbalance in 'region_chg' - wrong count at exit
> mm/hugetlb.c:5798:20: sparse: sparse: context imbalance in 'move_huge_pte' - different lock contexts for basic block
> mm/hugetlb.c: note: in included file:
> include/linux/mm.h:1391:22: sparse: sparse: context imbalance in 'hugetlb_wp' - unexpected unlock
> mm/hugetlb.c: note: in included file (through include/linux/hugetlb.h, include/linux/migrate.h):
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> --
> mm/userfaultfd.c:270:9: sparse: sparse: context imbalance in 'mfill_atomic_install_pte' - different lock contexts for basic block
> mm/userfaultfd.c:412:9: sparse: sparse: context imbalance in 'mfill_atomic_pte_zeropage' - different lock contexts for basic block
> mm/userfaultfd.c:498:9: sparse: sparse: context imbalance in 'mfill_atomic_pte_poison' - different lock contexts for basic block
> mm/userfaultfd.c: note: in included file:
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> mm/userfaultfd.c: note: in included file (through include/linux/rbtree.h, include/linux/mm_types.h, include/linux/mmzone.h, ...):
> include/linux/rcupdate.h:871:25: sparse: sparse: context imbalance in 'move_pages_pte' - unexpected unlock
>
> vim +90 include/linux/userfaultfd_k.h
>
> 87
> 88 static inline enum mfill_atomic_mode uffd_flags_get_mode(uffd_flags_t flags)
> 89 {
> > 90 return (enum mfill_atomic_mode)(flags & MFILL_ATOMIC_MODE_MASK);
> 91 }
> 92
Sigh.. I thought the cast would helped to tell sparse on this. Looks like
I need __force..
I'll squash below change when repost:
diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h
index 6064f9542d5b..6c5ca68204dd 100644
--- a/include/linux/userfaultfd_k.h
+++ b/include/linux/userfaultfd_k.h
@@ -87,7 +87,7 @@ extern vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason);
static inline enum mfill_atomic_mode uffd_flags_get_mode(uffd_flags_t flags)
{
- return (enum mfill_atomic_mode)(flags & MFILL_ATOMIC_MODE_MASK);
+ return (__force enum mfill_atomic_mode)(flags & MFILL_ATOMIC_MODE_MASK);
}
static inline bool uffd_flags_mode_is(uffd_flags_t flags, enum mfill_atomic_mode expected)
--
Peter Xu
© 2016 - 2025 Red Hat, Inc.