linux-ext4 - + ext3-wait-on-all-pending-commits-in-ext3_sync

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Message-Id: <200811031934.mA3JYJ5c023221@imap1.linux-foundation.org>
Date:	Mon, 03 Nov 2008 11:34:17 -0800
From:	akpm@...ux-foundation.org
To:	mm-commits@...r.kernel.org
Cc:	ajones@...erbed.com, linux-ext4@...r.kernel.org,
	sandeen@...hat.com, stable@...nel.org
Subject: + ext3-wait-on-all-pending-commits-in-ext3_sync_fs.patch added to -mm tree


The patch titled
     ext3: wait on all pending commits in ext3_sync_fs
has been added to the -mm tree.  Its filename is
     ext3-wait-on-all-pending-commits-in-ext3_sync_fs.patch

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*** Remember to use Documentation/SubmitChecklist when testing your code ***

See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find
out what to do about this

The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/

------------------------------------------------------
Subject: ext3: wait on all pending commits in ext3_sync_fs
From: Arthur Jones <ajones@...erbed.com>

In ext3_sync_fs, we only wait for a commit to finish if we started it, but
there may be one already in progress which will not be synced.

In the case of a data=ordered umount with pending long symlinks which are
delayed due to a long list of other I/O on the backing block device, this
causes the buffer associated with the long symlinks to not be moved to the
inode dirty list in the second phase of fsync_super.  Then, before they
can be dirtied again, kjournald exits, seeing the UMOUNT flag and the
dirty pages are never written to the backing block device, causing long
symlink corruption and exposing new or previously freed block data to
userspace.

This can be reproduced with a script created
by Eric Sandeen <sandeen@...hat.com>:

	#!/bin/bash

	umount /mnt/test2
	mount /dev/sdb4 /mnt/test2
	rm -f /mnt/test2/*
	dd if=/dev/zero of=/mnt/test2/bigfile bs=1M count=512
	touch
	/mnt/test2/thisisveryveryveryveryveryveryveryveryveryveryveryveryveryveryveryverylongfilename
	ln -s
	/mnt/test2/thisisveryveryveryveryveryveryveryveryveryveryveryveryveryveryveryverylongfilename
	/mnt/test2/link
	umount /mnt/test2
	mount /dev/sdb4 /mnt/test2
	ls /mnt/test2/
	umount /mnt/test2

To ensure all commits are synced, we flush all journal commits now when
sync_fs'ing ext3.

Signed-off-by: Arthur Jones <ajones@...erbed.com>
Eric Sandeen <sandeen@...hat.com>
Cc: <linux-ext4@...r.kernel.org>
Cc: <stable@...nel.org>		[2.6.everything]
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
---

 fs/ext3/super.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff -puN fs/ext3/super.c~ext3-wait-on-all-pending-commits-in-ext3_sync_fs fs/ext3/super.c
--- a/fs/ext3/super.c~ext3-wait-on-all-pending-commits-in-ext3_sync_fs
+++ a/fs/ext3/super.c
@@ -2396,7 +2396,13 @@ static int ext3_sync_fs(struct super_blo
 	if (journal_start_commit(EXT3_SB(sb)->s_journal, &target)) {
 		if (wait)
 			log_wait_commit(EXT3_SB(sb)->s_journal, target);
-	}
+	} else if (wait)
+		/*
+		 * We may have a commit in progress, clear it out
+		 * before we go on...
+		 */
+		ext3_force_commit(sb);
+
 	return 0;
 }
 
_

Patches currently in -mm which might be from ajones@...erbed.com are

ext3-wait-on-all-pending-commits-in-ext3_sync_fs.patch
forcedeth-power-down-phy-when-interface-is-down.patch

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