From: Andrew Ruder <andrew.ruder@elecsyscorp.com>
Date: Thu, 30 Jan 2014 15:26:54 +0000 (-0600)
Subject: fs/super.c: sync ro remount after blocking writers
X-Git-Tag: firefly_0821_release~176^2~4488^2~3
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=807612db2f9940b9fa6deaef054eb16d51bd3e00;p=firefly-linux-kernel-4.4.55.git

fs/super.c: sync ro remount after blocking writers

Move sync_filesystem() after sb_prepare_remount_readonly().  If writers
sneak in anywhere from sync_filesystem() to sb_prepare_remount_readonly()
it can cause inodes to be dirtied and writeback to occur well after
sys_mount() has completely successfully.

This was spotted by corrupted ubifs filesystems on reboot, but appears
that it can cause issues with any filesystem using writeback.

Cc: Artem Bityutskiy <dedekind1@gmail.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
CC: Richard Weinberger <richard@nod.at>
Co-authored-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Andrew Ruder <andrew.ruder@elecsyscorp.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---

diff --git a/fs/super.c b/fs/super.c
index cecd780e0f44..80d5cf2ca765 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -703,7 +703,6 @@ int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
 	if (flags & MS_RDONLY)
 		acct_auto_close(sb);
 	shrink_dcache_sb(sb);
-	sync_filesystem(sb);
 
 	remount_ro = (flags & MS_RDONLY) && !(sb->s_flags & MS_RDONLY);
 
@@ -720,6 +719,8 @@ int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
 		}
 	}
 
+	sync_filesystem(sb);
+
 	if (sb->s_op->remount_fs) {
 		retval = sb->s_op->remount_fs(sb, &flags, data);
 		if (retval) {