linux-sg2042/fs/jbd
Jan Kara 8fe4cd0dc5 jbd: fix return value of journal_start_commit()
journal_start_commit() returns 1 if either a transaction is committing or
the function has queued a transaction commit.  But it returns 0 if we
raced with somebody queueing the transaction commit as well.  This
resulted in ext3_sync_fs() not functioning correctly (description from
Arthur Jones): 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@redhat.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/

This patch fixes journal_start_commit() to always return 1 when there's
a transaction committing or queued for commit.

Cc: Eric Sandeen <sandeen@redhat.com>
Cc: Mike Snitzer <snitzer@gmail.com>
Cc: <linux-ext4@vger.kernel.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-02-11 14:25:35 -08:00
..
Kconfig fs/Kconfig: move ext2, ext3, ext4, JBD, JBD2 out 2008-10-20 11:43:59 -07:00
Makefile Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
checkpoint.c jbd: don't give up looking for space so easily in __log_wait_for_space 2008-11-06 22:37:59 -05:00
commit.c jbd: improve fsync batching 2009-01-08 08:31:00 -08:00
journal.c jbd: fix return value of journal_start_commit() 2009-02-11 14:25:35 -08:00
recovery.c jbd: fix error handling for checkpoint io 2008-10-23 08:55:01 -07:00
revoke.c jbd: tidy up revoke cache initialisation and destruction 2008-07-25 10:53:32 -07:00
transaction.c jbd: remove excess kernel-doc notation 2009-01-08 08:31:01 -08:00