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Message-Id: <20200227132212.943520725@linuxfoundation.org>
Date: Thu, 27 Feb 2020 14:35:23 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, Zhihao Cheng <chengzhihao1@...wei.com>,
"zhangyi (F)" <yi.zhang@...wei.com>, Stable@...r.kernel.org,
Richard Weinberger <richard@....at>
Subject: [PATCH 4.4 007/113] ubifs: Fix deadlock in concurrent bulk-read and writepage
From: Zhihao Cheng <chengzhihao1@...wei.com>
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 <chengzhihao1@...wei.com>
Suggested-by: zhangyi (F) <yi.zhang@...wei.com>
Cc: <Stable@...r.kernel.org>
Fixes: 4793e7c5e1c ("UBIFS: add bulk-read facility")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=206153
Signed-off-by: Richard Weinberger <richard@....at>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
fs/ubifs/file.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
--- a/fs/ubifs/file.c
+++ b/fs/ubifs/file.c
@@ -782,8 +782,9 @@ static int ubifs_do_bulk_read(struct ubi
if (page_offset > end_index)
break;
- page = find_or_create_page(mapping, page_offset,
- GFP_NOFS | __GFP_COLD);
+ page = pagecache_get_page(mapping, page_offset,
+ FGP_LOCK|FGP_ACCESSED|FGP_CREAT|FGP_NOWAIT,
+ GFP_NOFS | __GFP_COLD);
if (!page)
break;
if (!PageUptodate(page))
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