On Wed, May 13, 2026 at 08:39:33AM -0700, 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;
> }
> 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).
Did you test this patch series? I don't see how we ever get to
-ENOTRECOVERABLE there ...
Even with MF_COUNT_INCREASED, the first pass does:
if (flags & MF_COUNT_INCREASED)
count_increased = true;
[...]
if (PageHuge(p) || HWPoisonHandlable(p, flags)) {
ret = 1;
} else {
if (pass++ < GET_PAGE_MAX_RETRY_NUM) { <-
put_page(p);
shake_page(p);
count_increased = false;
goto try_again; <-
}
put_page(p);
ret = -ENOTRECOVERABLE;
}
Then we come back with count_increased=false:
try_again:
if (!count_increased) {
ret = __get_hwpoison_page(p, flags); <-
if (!ret) {
[...]
} else if (ret == -EBUSY) { <-
[...]
ret = -EIO;
goto out; <-
}
}
For slab/vmalloc/page-table pages, __get_hwpoison_page() returns -EBUSY:
if (!HWPoisonHandlable(&folio->page, flags))
return -EBUSY;
so they still seem to end up as -EIO ... Am I missing something?
> */
> static int get_hwpoison_page(struct page *p, unsigned long flags)
> {
>
>--
>2.53.0-Meta
>
>
