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fs/hugetlbfs/inode.c: mm/memory-failure.c: fix hugetlbfs hwpoison han…
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has_extra_refcount() makes the assumption that the page cache adds a ref
count of 1 and subtracts this in the extra_pins case.  Commit a08c719
(mm/filemap: remove hugetlb special casing in filemap.c) modifies
__filemap_add_folio() by calling folio_ref_add(folio, nr); for all cases
(including hugtetlb) where nr is the number of pages in the folio.  We
should adjust the number of references coming from the page cache by
subtracing the number of pages rather than 1.

In hugetlbfs_read_iter(), folio_test_has_hwpoisoned() is testing the wrong
flag as, in the hugetlb case, memory-failure code calls
folio_test_set_hwpoison() to indicate poison.  folio_test_hwpoison() is
the correct function to test for that flag.

After these fixes, the hugetlb hwpoison read selftest passes all cases.

Link: https://lkml.kernel.org/r/20240112180840.367006-1-sidhartha.kumar@oracle.com
Fixes: a08c719 ("mm/filemap: remove hugetlb special casing in filemap.c")
Signed-off-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Closes: https://lore.kernel.org/linux-mm/20230713001833.3778937-1-jiaqiyan@google.com/T/#m8e1469119e5b831bbd05d495f96b842e4a1c5519
Reported-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
Tested-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
Acked-by: Miaohe Lin <linmiaohe@huawei.com>
Acked-by: Muchun Song <muchun.song@linux.dev>
Cc: James Houghton <jthoughton@google.com>
Cc: Jiaqi Yan <jiaqiyan@google.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: <stable@vger.kernel.org>	[6.7+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Sidhartha Kumar authored and Andrew Morton committed Jan 26, 2024
1 parent ab4443f commit 19d3e22
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Showing 2 changed files with 2 additions and 2 deletions.
2 changes: 1 addition & 1 deletion fs/hugetlbfs/inode.c
Original file line number Diff line number Diff line change
Expand Up @@ -340,7 +340,7 @@ static ssize_t hugetlbfs_read_iter(struct kiocb *iocb, struct iov_iter *to)
} else {
folio_unlock(folio);

if (!folio_test_has_hwpoisoned(folio))
if (!folio_test_hwpoison(folio))
want = nr;
else {
/*
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2 changes: 1 addition & 1 deletion mm/memory-failure.c
Original file line number Diff line number Diff line change
Expand Up @@ -982,7 +982,7 @@ static bool has_extra_refcount(struct page_state *ps, struct page *p,
int count = page_count(p) - 1;

if (extra_pins)
count -= 1;
count -= folio_nr_pages(page_folio(p));

if (count > 0) {
pr_err("%#lx: %s still referenced by %d users\n",
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