On 2026/5/13 23:39, Breno Leitao wrote:
> get_any_page() collapses three different failure modes into a single
> -EIO return:
>
> * the put_page race in the !count_increased path;
> * the HWPoisonHandlable() rejection that bounces out of
> __get_hwpoison_page() with -EBUSY and exhausts shake_page() retries;
> * the HWPoisonHandlable() rejection that goes through the
> count_increased / put_page / shake_page retry loop.
>
> The first is transient (the page is racing with the allocator). The
> second can be either transient (a userspace folio briefly off LRU
> during migration/compaction) or stable (slab/vmalloc/page-table/
> kernel-stack pages). The third describes a stable kernel-owned page
> that the count_increased=true caller already held a reference on.
>
> Distinguish them on the return path: keep -EIO for both the put_page
> race and the -EBUSY-after-retries branch (shake_page() cannot drag a
> folio back from active migration, so we cannot prove the page is
> permanently kernel-owned from there), keep -EBUSY for the allocation
> race (unchanged), and return -ENOTRECOVERABLE only from the
> count_increased-true HWPoisonHandlable() rejection that exhausts its
> retries -- the caller's reference is structural evidence that the
> page is owned by the kernel.
>
> Extend the unhandlable-page pr_err() to fire for either errno and
> update the get_hwpoison_page() kerneldoc.
>
> memory_failure() still folds every negative return into
> MF_MSG_GET_HWPOISON via its existing "else if (res < 0)" branch, so
> this patch is a no-op for users of memory_failure() and only changes
> the errno that soft_offline_page() can propagate to its callers. A
> follow-up wires the new return code through memory_failure() and
> reports MF_MSG_KERNEL for the unrecoverable cases.
>
> Suggested-by: David Hildenbrand <[email protected]>
> Signed-off-by: Breno Leitao <[email protected]>
> ---
> mm/memory-failure.c | 18 +++++++++++++++---
> 1 file changed, 15 insertions(+), 3 deletions(-)
>
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 49bcfbd04d213..bae883df3ccb2 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1408,6 +1408,15 @@ static int get_any_page(struct page *p, unsigned long
> flags)
> shake_page(p);
> goto try_again;
> }
> + /*
> + * Return -EIO rather than -ENOTRECOVERABLE: this
> + * branch is also reached for pages that are merely
> + * off-LRU transiently (e.g. a folio in the middle
> + * of migration or compaction), which shake_page()
> + * cannot drag back. The caller cannot prove the
> + * page is permanently kernel-owned from here, so
> + * keep it on the recoverable errno.
> + */
> ret = -EIO;
> goto out;
> }
> @@ -1427,10 +1436,10 @@ static int get_any_page(struct page *p, unsigned long
> flags)
> goto try_again;
> }
> put_page(p);
> - ret = -EIO;
> + ret = -ENOTRECOVERABLE;
Theoretically, pages that are merely off-LRU transiently as you commented above
could
reach here too? Or am I miss something?
Thanks.
.
> }
> out:
> - if (ret == -EIO)
> + if (ret == -EIO || ret == -ENOTRECOVERABLE)
> pr_err("%#lx: unhandlable page.\n", page_to_pfn(p));
>
> return ret;
> @@ -1487,7 +1496,10 @@ static int __get_unpoison_page(struct page *page)
> * -EIO for pages on which we can not handle memory errors,
> * -EBUSY when get_hwpoison_page() has raced with page lifecycle
> * operations like allocation and free,
> - * -EHWPOISON when the page is hwpoisoned and taken off from buddy.
> + * -EHWPOISON when the page is hwpoisoned and taken off from buddy,
> + * -ENOTRECOVERABLE for stable kernel-owned pages the handler
> + * cannot recover (PG_reserved, slab, vmalloc, page tables,
> + * kernel stacks, and similar non-LRU/non-buddy pages).
> */
> static int get_hwpoison_page(struct page *p, unsigned long flags)
> {
>
