Patchwork [171/222] ext4: do not try to write superblock on ro remount w/o journal

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Submitter Herton Ronaldo Krzesinski
Date Jan. 16, 2013, 3:56 p.m.
Message ID <>
Download mbox | patch
Permalink /patch/212748/
State New
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Herton Ronaldo Krzesinski - Jan. 16, 2013, 3:56 p.m. -stable review patch.  If anyone has any objections, please let me know.


From: Michael Tokarev <>

commit d096ad0f79a782935d2e06ae8fb235e8c5397775 upstream.

When a journal-less ext4 filesystem is mounted on a read-only block
device (blockdev --setro will do), each remount (for other, unrelated,
flags, like suid=>nosuid etc) results in a series of scary messages
from kernel telling about I/O errors on the device.

This is becauese of the following code ext4_remount():

       if (sbi->s_journal == NULL)
                ext4_commit_super(sb, 1);

at the end of remount procedure, which forces writing (flushing) of
a superblock regardless whenever it is dirty or not, if the filesystem
is readonly or not, and whenever the device itself is readonly or not.

We only need call ext4_commit_super when the file system had been
previously mounted read/write.

Thanks to Eric Sandeen for help in diagnosing this issue.

Signed-off-By: Michael Tokarev <>
Signed-off-by: "Theodore Ts'o" <>
Signed-off-by: Herton Ronaldo Krzesinski <>
 fs/ext4/super.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)


diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index b045207..5be2105 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -4686,7 +4686,7 @@  static int ext4_remount(struct super_block *sb, int *flags, char *data)
-	if (sbi->s_journal == NULL)
+	if (sbi->s_journal == NULL && !(old_sb_flags & MS_RDONLY))
 		ext4_commit_super(sb, 1);