+ mm-filemap-fix-find_lock_entries-hang-on-32-bit-thp.patch added to -mm tree

[akpm@linux-foundation.org]

The patch titled
     Subject: mm/filemap: fix find_lock_entries hang on 32-bit THP
has been added to the -mm tree.  Its filename is
     mm-filemap-fix-find_lock_entries-hang-on-32-bit-thp.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mm-filemap-fix-find_lock_entries-hang-on-32-bit-thp.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-filemap-fix-find_lock_entries-hang-on-32-bit-thp.patch

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------------------------------------------------------
From: Hugh Dickins <hughd@google.com>
Subject: 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 4.13's 0cc3b0ec23ce ("Clarify
(and fix) 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: 5c211ba29deb ("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>
---

 mm/filemap.c |   10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

--- a/mm/filemap.c~mm-filemap-fix-find_lock_entries-hang-on-32-bit-thp
+++ a/mm/filemap.c
@@ -1969,8 +1969,14 @@ unlock:
 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();
 
_

Patches currently in -mm which might be from hughd@google.com are

mm-filemap-fix-find_lock_entries-hang-on-32-bit-thp.patch
mm-filemap-fix-mapping_seek_hole_data-on-thp-32-bit.patch
mm-restore-node-stat-checking-in-proc-sys-vm-stat_refresh.patch
mm-no-more-einval-from-proc-sys-vm-stat_refresh.patch
mm-proc-sys-vm-stat_refresh-skip-checking-known-negative-stats.patch
mm-proc-sys-vm-stat_refresh-stop-checking-monotonic-numa-stats.patch