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Subject[PATCH 5.5 105/367] ubifs: Fix deadlock in concurrent bulk-read and writepage
From: Zhihao Cheng <>

commit f5de5b83303e61b1f3fb09bd77ce3ac2d7a475f2 upstream.

In ubifs, concurrent execution of writepage and bulk read on the same file
may cause ABBA deadlock, for example (Reproduce method see Link):

Process A(Bulk-read starts from page4) Process B(write page4 back)
vfs_read wb_workfn or fsync
... ...
generic_file_buffered_read write_cache_pages
ubifs_readpage LOCK(page4)

ubifs_bulk_read ubifs_writepage
LOCK(ui->ui_mutex) ubifs_write_inode

ubifs_do_bulk_read LOCK(ui->ui_mutex)
find_or_create_page(alloc page4) ↑
LOCK(page4) <-- ABBA deadlock occurs!

In order to ensure the serialization execution of bulk read, we can't
remove the big lock 'ui->ui_mutex' in ubifs_bulk_read(). Instead, we
allow ubifs_do_bulk_read() to lock page failed by replacing
find_or_create_page(FGP_LOCK) with
pagecache_get_page(FGP_LOCK | FGP_NOWAIT).

Signed-off-by: Zhihao Cheng <>
Suggested-by: zhangyi (F) <>
Cc: <>
Fixes: 4793e7c5e1c ("UBIFS: add bulk-read facility")
Signed-off-by: Richard Weinberger <>
Signed-off-by: Greg Kroah-Hartman <>

fs/ubifs/file.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

--- a/fs/ubifs/file.c
+++ b/fs/ubifs/file.c
@@ -786,7 +786,9 @@ static int ubifs_do_bulk_read(struct ubi

if (page_offset > end_index)
- page = find_or_create_page(mapping, page_offset, ra_gfp_mask);
+ page = pagecache_get_page(mapping, page_offset,
+ ra_gfp_mask);
if (!page)
if (!PageUptodate(page))

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