[lkml]   [2012]   [Mar]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: [PATCH v1 0/9] do not use s_dirt in ext4
    On Thu, 2012-03-22 at 11:33 +0100, Jan Kara wrote:
    > Then we have ext4_mark_super_dirty() call from 4 places - I forgot about
    > these originally... I kind of miss their purpose. Originally they were used
    > so that we write total number of free blocks and inodes in the superblock
    > but when we do not maintain them in the journal mode I don't see a reason
    > to periodically sync them in no-journal mode. Ted, what is the purpose of
    > these calls?

    I do not understand what's the fundamental difference between journal
    and non-journal mode. Why when we do have the journal we do not mark the
    super-block as dirty in many places (e.g., in 'ext4_file_open()' - if we
    do have the journal, when do we make sure we save the mount point path

    May be it has something to do with behaving like the ext2 driver when
    mounting ext2-formatted media with the the ext4 driver?

    Jan, since Ted did not answer, may be you can figure out the reasons
    from this commit message, which actually introduced the
    'ext4_mark_super_dirty()' function?

    commit a0375156ca1041574b5d47cc7e32f10b891151b0
    Author: Theodore Ts'o <>
    Date: Fri Jun 11 23:14:04 2010 -0400

    ext4: Clean up s_dirt handling

    We don't need to set s_dirt in most of the ext4 code when journaling
    is enabled. In ext3/4 some of the summary statistics for # of free
    inodes, blocks, and directories are calculated from the per-block
    group statistics when the file system is mounted or unmounted. As a
    result the superblock doesn't have to be updated, either via the
    journal or by setting s_dirt. There are a few exceptions, most
    notably when resizing the file system, where the superblock needs to
    be modified --- and in that case it should be done as a journalled
    operation if possible, and s_dirt set only in no-journal mode.

    This patch will optimize out some unneeded disk writes when using ext4
    with a journal.

    Signed-off-by: "Theodore Ts'o" <>

    Best Regards,
    Artem Bityutskiy
    [unhandled content-type:application/pgp-signature]
     \ /
      Last update: 2012-03-27 15:29    [W:0.022 / U:107.844 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site