linux-kernel - [PATCH 4.4 30/46] f2fs: do not wait for writeback in write

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Message-Id: <20171019134847.306952519@linuxfoundation.org>
Date:   Thu, 19 Oct 2017 15:49:06 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Chao Yu <yuchao0@...wei.com>,
        Jaegeuk Kim <jaegeuk@...nel.org>,
        Sasha Levin <alexander.levin@...izon.com>
Subject: [PATCH 4.4 30/46] f2fs: do not wait for writeback in write_begin

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jaegeuk Kim <jaegeuk@...nel.org>


[ Upstream commit 86d54795c94532075d862aa0a79f0c981dab4bdd ]

Otherwise we can get livelock like below.

[79880.428136] dbench          D    0 18405  18404 0x00000000
[79880.428139] Call Trace:
[79880.428142]  __schedule+0x219/0x6b0
[79880.428144]  schedule+0x36/0x80
[79880.428147]  schedule_timeout+0x243/0x2e0
[79880.428152]  ? update_sd_lb_stats+0x16b/0x5f0
[79880.428155]  ? ktime_get+0x3c/0xb0
[79880.428157]  io_schedule_timeout+0xa6/0x110
[79880.428161]  __lock_page+0xf7/0x130
[79880.428164]  ? unlock_page+0x30/0x30
[79880.428167]  pagecache_get_page+0x16b/0x250
[79880.428171]  grab_cache_page_write_begin+0x20/0x40
[79880.428182]  f2fs_write_begin+0xa2/0xdb0 [f2fs]
[79880.428192]  ? f2fs_mark_inode_dirty_sync+0x16/0x30 [f2fs]
[79880.428197]  ? kmem_cache_free+0x79/0x200
[79880.428203]  ? __mark_inode_dirty+0x17f/0x360
[79880.428206]  generic_perform_write+0xbb/0x190
[79880.428213]  ? file_update_time+0xa4/0xf0
[79880.428217]  __generic_file_write_iter+0x19b/0x1e0
[79880.428226]  f2fs_file_write_iter+0x9c/0x180 [f2fs]
[79880.428231]  __vfs_write+0xc5/0x140
[79880.428235]  vfs_write+0xb2/0x1b0
[79880.428238]  SyS_write+0x46/0xa0
[79880.428242]  entry_SYSCALL_64_fastpath+0x1e/0xad

Fixes: cae96a5c8ab6 ("f2fs: check io submission more precisely")
Reviewed-by: Chao Yu <yuchao0@...wei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/f2fs/data.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -1416,7 +1416,12 @@ static int f2fs_write_begin(struct file
 			goto fail;
 	}
 repeat:
-	page = grab_cache_page_write_begin(mapping, index, flags);
+	/*
+	 * Do not use grab_cache_page_write_begin() to avoid deadlock due to
+	 * wait_for_stable_page. Will wait that below with our IO control.
+	 */
+	page = pagecache_get_page(mapping, index,
+				FGP_LOCK | FGP_WRITE | FGP_CREAT, GFP_NOFS);
 	if (!page) {
 		err = -ENOMEM;
 		goto fail;