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mm/filemap: fix find_lock_entries hang on 32-bit THP 

No problem on 64-bit, or without huge pages, but xfstests generic/308
hung uninterruptibly on 32-bit huge tmpfs.

Since commit 0cc3b0ec23 ("Clarify (and fix) in 4.13 MAX_LFS_FILESIZE
macros"), MAX_LFS_FILESIZE is only a PAGE_SIZE away from wrapping 32-bit
xa_index to 0, so the new find_lock_entries() has to be extra careful
when handling a THP.

Link: https://lkml.kernel.org/r/alpine.LSU.2.11.2104211735430.3299@eggly.anvils
Fixes: 5c211ba29d ("mm: add and use find_lock_entries")
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: William Kucharski <william.kucharski@oracle.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Jan Kara <jack@suse.cz>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Yang Shi <yang.shi@linux.alibaba.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Hugh Dickins 2021-04-23 14:28:57 -07:00 committed by Linus Torvalds
parent 2896900e22
commit 2d11e73815
1 changed files with 8 additions and 2 deletions
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10
mm/filemap.c
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@ -1969,8 +1969,14 @@ unsigned find_lock_entries(struct address_space *mapping, pgoff_t start,
put:
put_page(page);
next:
if (!xa_is_value(page) && PageTransHuge(page))
xas_set(&xas, page->index + thp_nr_pages(page));
if (!xa_is_value(page) && PageTransHuge(page)) {
unsigned int nr_pages = thp_nr_pages(page);
/* Final THP may cross MAX_LFS_FILESIZE on 32-bit */
xas_set(&xas, page->index + nr_pages);
if (xas.xa_index < nr_pages)
break;
}
}
rcu_read_unlock();