• Jan Kara's avatar
    jbd: fix return value of journal_start_commit() · 8fe4cd0d
    Jan Kara authored
    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: default avatarJan Kara <jack@suse.cz>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    8fe4cd0d
journal.c 53 KB