Large block size (LBS) folios cannot be split to order-0 folios but
min_order_for_folio(). Current split fails directly, but that is not
optimal. Split the folio to min_order_for_folio(), so that, after split,
only the folio containing the poisoned page becomes unusable instead.
For soft offline, do not split the large folio if its min_order_for_folio()
is not 0. Since the folio is still accessible from userspace and premature
split might lead to potential performance loss.
Suggested-by: Jane Chu <jane.chu@oracle.com>
Signed-off-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
---
mm/memory-failure.c | 31 +++++++++++++++++++++++++++----
1 file changed, 27 insertions(+), 4 deletions(-)
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index f698df156bf8..acc35c881547 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1656,12 +1656,13 @@ static int identify_page_state(unsigned long pfn, struct page *p,
* there is still more to do, hence the page refcount we took earlier
* is still needed.
*/
-static int try_to_split_thp_page(struct page *page, bool release)
+static int try_to_split_thp_page(struct page *page, unsigned int new_order,
+ bool release)
{
int ret;
lock_page(page);
- ret = split_huge_page(page);
+ ret = split_huge_page_to_order(page, new_order);
unlock_page(page);
if (ret && release)
@@ -2280,6 +2281,9 @@ int memory_failure(unsigned long pfn, int flags)
folio_unlock(folio);
if (folio_test_large(folio)) {
+ const int new_order = min_order_for_split(folio);
+ int err;
+
/*
* The flag must be set after the refcount is bumped
* otherwise it may race with THP split.
@@ -2294,7 +2298,16 @@ int memory_failure(unsigned long pfn, int flags)
* page is a valid handlable page.
*/
folio_set_has_hwpoisoned(folio);
- if (try_to_split_thp_page(p, false) < 0) {
+ err = try_to_split_thp_page(p, new_order, /* release= */ false);
+ /*
+ * If splitting a folio to order-0 fails, kill the process.
+ * Split the folio regardless to minimize unusable pages.
+ * Because the memory failure code cannot handle large
+ * folios, this split is always treated as if it failed.
+ */
+ if (err || new_order) {
+ /* get folio again in case the original one is split */
+ folio = page_folio(p);
res = -EHWPOISON;
kill_procs_now(p, pfn, flags, folio);
put_page(p);
@@ -2621,7 +2634,17 @@ static int soft_offline_in_use_page(struct page *page)
};
if (!huge && folio_test_large(folio)) {
- if (try_to_split_thp_page(page, true)) {
+ const int new_order = min_order_for_split(folio);
+
+ /*
+ * If new_order (target split order) is not 0, do not split the
+ * folio at all to retain the still accessible large folio.
+ * NOTE: if minimizing the number of soft offline pages is
+ * preferred, split it to non-zero new_order like it is done in
+ * memory_failure().
+ */
+ if (new_order || try_to_split_thp_page(page, /* new_order= */ 0,
+ /* release= */ true)) {
pr_info("%#lx: thp split failed\n", pfn);
return -EBUSY;
}
--
2.43.0On 30.10.25 02:40, Zi Yan wrote: > Large block size (LBS) folios cannot be split to order-0 folios but > min_order_for_folio(). Current split fails directly, but that is not > optimal. Split the folio to min_order_for_folio(), so that, after split, > only the folio containing the poisoned page becomes unusable instead. > > For soft offline, do not split the large folio if its min_order_for_folio() > is not 0. Since the folio is still accessible from userspace and premature > split might lead to potential performance loss. > > Suggested-by: Jane Chu <jane.chu@oracle.com> > Signed-off-by: Zi Yan <ziy@nvidia.com> > Reviewed-by: Luis Chamberlain <mcgrof@kernel.org> > Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> > --- Acked-by: David Hildenbrand <david@redhat.com> -- Cheers David / dhildenb
On Wed, Oct 29, 2025 at 09:40:19PM -0400, Zi Yan wrote: >Large block size (LBS) folios cannot be split to order-0 folios but >min_order_for_folio(). Current split fails directly, but that is not >optimal. Split the folio to min_order_for_folio(), so that, after split, >only the folio containing the poisoned page becomes unusable instead. > >For soft offline, do not split the large folio if its min_order_for_folio() >is not 0. Since the folio is still accessible from userspace and premature >split might lead to potential performance loss. > >Suggested-by: Jane Chu <jane.chu@oracle.com> >Signed-off-by: Zi Yan <ziy@nvidia.com> >Reviewed-by: Luis Chamberlain <mcgrof@kernel.org> >Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Looks reasonable. Reviewed-by: Wei Yang <richard.weiyang@gmail.com> -- Wei Yang Help you, Help me
On 2025/10/30 9:40, Zi Yan wrote: > Large block size (LBS) folios cannot be split to order-0 folios but > min_order_for_folio(). Current split fails directly, but that is not > optimal. Split the folio to min_order_for_folio(), so that, after split, > only the folio containing the poisoned page becomes unusable instead. > > For soft offline, do not split the large folio if its min_order_for_folio() > is not 0. Since the folio is still accessible from userspace and premature > split might lead to potential performance loss. > > Suggested-by: Jane Chu <jane.chu@oracle.com> > Signed-off-by: Zi Yan <ziy@nvidia.com> > Reviewed-by: Luis Chamberlain <mcgrof@kernel.org> > Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Reviewed-by: Miaohe Lin <linmiaohe@huawei.com> Thanks. .
On Thu, Oct 30, 2025 at 9:40 AM Zi Yan <ziy@nvidia.com> wrote:
>
> Large block size (LBS) folios cannot be split to order-0 folios but
> min_order_for_folio(). Current split fails directly, but that is not
> optimal. Split the folio to min_order_for_folio(), so that, after split,
> only the folio containing the poisoned page becomes unusable instead.
>
> For soft offline, do not split the large folio if its min_order_for_folio()
> is not 0. Since the folio is still accessible from userspace and premature
> split might lead to potential performance loss.
>
> Suggested-by: Jane Chu <jane.chu@oracle.com>
> Signed-off-by: Zi Yan <ziy@nvidia.com>
> Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Barry Song <baohua@kernel.org>
> ---
> mm/memory-failure.c | 31 +++++++++++++++++++++++++++----
> 1 file changed, 27 insertions(+), 4 deletions(-)
>
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index f698df156bf8..acc35c881547 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
...
> @@ -2294,7 +2298,16 @@ int memory_failure(unsigned long pfn, int flags)
> * page is a valid handlable page.
> */
> folio_set_has_hwpoisoned(folio);
> - if (try_to_split_thp_page(p, false) < 0) {
> + err = try_to_split_thp_page(p, new_order, /* release= */ false);
> + /*
> + * If splitting a folio to order-0 fails, kill the process.
> + * Split the folio regardless to minimize unusable pages.
> + * Because the memory failure code cannot handle large
> + * folios, this split is always treated as if it failed.
> + */
> + if (err || new_order) {
> + /* get folio again in case the original one is split */
> + folio = page_folio(p);
It’s a bit hard to follow that we implicitly use p to get its original
folio for splitting in try_to_split_thp_page(), and then again use p to
get its new folio for kill_procs_now(). It might be more readable to move
try_to_split_thp_page() into a helper like try_to_split_folio(folio, …),
so it’s explicit that we’re splitting a folio rather than a page?
Thanks
Barry
On 2025/10/30 09:40, Zi Yan wrote:
> Large block size (LBS) folios cannot be split to order-0 folios but
> min_order_for_folio(). Current split fails directly, but that is not
> optimal. Split the folio to min_order_for_folio(), so that, after split,
> only the folio containing the poisoned page becomes unusable instead.
>
> For soft offline, do not split the large folio if its min_order_for_folio()
> is not 0. Since the folio is still accessible from userspace and premature
> split might lead to potential performance loss.
>
> Suggested-by: Jane Chu <jane.chu@oracle.com>
> Signed-off-by: Zi Yan <ziy@nvidia.com>
> Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
> ---
LGTM! Feel free to add:
Reviewed-by: Lance Yang <lance.yang@linux.dev>
> mm/memory-failure.c | 31 +++++++++++++++++++++++++++----
> 1 file changed, 27 insertions(+), 4 deletions(-)
>
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index f698df156bf8..acc35c881547 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1656,12 +1656,13 @@ static int identify_page_state(unsigned long pfn, struct page *p,
> * there is still more to do, hence the page refcount we took earlier
> * is still needed.
> */
> -static int try_to_split_thp_page(struct page *page, bool release)
> +static int try_to_split_thp_page(struct page *page, unsigned int new_order,
> + bool release)
> {
> int ret;
>
> lock_page(page);
> - ret = split_huge_page(page);
> + ret = split_huge_page_to_order(page, new_order);
> unlock_page(page);
>
> if (ret && release)
> @@ -2280,6 +2281,9 @@ int memory_failure(unsigned long pfn, int flags)
> folio_unlock(folio);
>
> if (folio_test_large(folio)) {
> + const int new_order = min_order_for_split(folio);
> + int err;
> +
> /*
> * The flag must be set after the refcount is bumped
> * otherwise it may race with THP split.
> @@ -2294,7 +2298,16 @@ int memory_failure(unsigned long pfn, int flags)
> * page is a valid handlable page.
> */
> folio_set_has_hwpoisoned(folio);
> - if (try_to_split_thp_page(p, false) < 0) {
> + err = try_to_split_thp_page(p, new_order, /* release= */ false);
> + /*
> + * If splitting a folio to order-0 fails, kill the process.
> + * Split the folio regardless to minimize unusable pages.
> + * Because the memory failure code cannot handle large
> + * folios, this split is always treated as if it failed.
> + */
> + if (err || new_order) {
> + /* get folio again in case the original one is split */
> + folio = page_folio(p);
> res = -EHWPOISON;
> kill_procs_now(p, pfn, flags, folio);
> put_page(p);
> @@ -2621,7 +2634,17 @@ static int soft_offline_in_use_page(struct page *page)
> };
>
> if (!huge && folio_test_large(folio)) {
> - if (try_to_split_thp_page(page, true)) {
> + const int new_order = min_order_for_split(folio);
> +
> + /*
> + * If new_order (target split order) is not 0, do not split the
> + * folio at all to retain the still accessible large folio.
> + * NOTE: if minimizing the number of soft offline pages is
> + * preferred, split it to non-zero new_order like it is done in
> + * memory_failure().
> + */
> + if (new_order || try_to_split_thp_page(page, /* new_order= */ 0,
> + /* release= */ true)) {
> pr_info("%#lx: thp split failed\n", pfn);
> return -EBUSY;
> }
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