+ fs-hugetlbfs-inodec-mm-memory-failurec-fix-hugetlbfs-hwpoison-handling.patch added to mm-hotfixes-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: fs/hugetlbfs/inode.c: mm/memory-failure.c: fix hugetlbfs hwpoison handling
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     fs-hugetlbfs-inodec-mm-memory-failurec-fix-hugetlbfs-hwpoison-handling.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/fs-hugetlbfs-inodec-mm-memory-failurec-fix-hugetlbfs-hwpoison-handling.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Subject: fs/hugetlbfs/inode.c: mm/memory-failure.c: fix hugetlbfs hwpoison handling
Date: Fri, 12 Jan 2024 10:08:40 -0800

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 a08c7193e4f1
(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: a08c7193e4f1 ("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>
Cc: James Houghton <jthoughton@google.com>
Cc: Jiaqi Yan <jiaqiyan@google.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: <stable@vger.kernel.org>	[6.7+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/hugetlbfs/inode.c |    2 +-
 mm/memory-failure.c  |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

--- a/fs/hugetlbfs/inode.c~fs-hugetlbfs-inodec-mm-memory-failurec-fix-hugetlbfs-hwpoison-handling
+++ a/fs/hugetlbfs/inode.c
@@ -340,7 +340,7 @@ static ssize_t hugetlbfs_read_iter(struc
 		} else {
 			folio_unlock(folio);
 
-			if (!folio_test_has_hwpoisoned(folio))
+			if (!folio_test_hwpoison(folio))
 				want = nr;
 			else {
 				/*
--- a/mm/memory-failure.c~fs-hugetlbfs-inodec-mm-memory-failurec-fix-hugetlbfs-hwpoison-handling
+++ a/mm/memory-failure.c
@@ -982,7 +982,7 @@ static bool has_extra_refcount(struct pa
 	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",
_

Patches currently in -mm which might be from sidhartha.kumar@oracle.com are

fs-hugetlbfs-inodec-mm-memory-failurec-fix-hugetlbfs-hwpoison-handling.patch
maple_tree-fix-comment-describing-mas_node_count_gfp.patch