Patchwork [3.5.y.z,extended,stable] Patch "ext4: do not try to write superblock on ro remount w/o" has been added to staging queue

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Submitter Herton Ronaldo Krzesinski
Date Jan. 10, 2013, 9:02 p.m.
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Download mbox | patch
Permalink /patch/211151/
State New
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Herton Ronaldo Krzesinski - Jan. 10, 2013, 9:02 p.m.
This is a note to let you know that I have just added a patch titled

    ext4: do not try to write superblock on ro remount w/o

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see



From d3749db7fb1267de2851c88eca4f2be1cfcd2dae Mon Sep 17 00:00:00 2001
From: Michael Tokarev <>
Date: Tue, 25 Dec 2012 14:08:16 -0500
Subject: [PATCH] ext4: do not try to write superblock on ro remount w/o

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);