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    Subject[PATCH] [GFS2] flush the glock completely in inode_go_sync
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    From: Benjamin Marzinski <bmarzins@redhat.com>

    Fix for bz #231910
    When filemap_fdatawrite() is called on the inode mapping in data=ordered mode,
    it will add the glock to the log. In inode_go_sync(), if you do the
    gfs2_log_flush() before this, after the filemap_fdatawrite() call, the glock
    and its associated data buffers will be on the log again. This means you can
    demote a lock from exclusive, without having it flushed from the log. The
    attached patch simply moves the gfs2_log_flush up to after the
    filemap_fdatawrite() call.

    Originally, I tried moving the gfs2_log_flush to after gfs2_meta_sync(), but
    that caused me to trip the following assert.

    GFS2: fsid=cypher-36:test.0: fatal: assertion "!buffer_busy(bh)" failed
    GFS2: fsid=cypher-36:test.0: function = gfs2_ail_empty_gl, file = fs/gfs2/glops.c, line = 61

    It appears that gfs2_log_flush() puts some of the glocks buffers in the busy
    state and the filemap_fdatawrite() call is necessary to flush them. This makes
    me worry slightly that a related problem could happen because of moving the
    gfs2_log_flush() after the initial filemap_fdatawrite(), but I assume that
    gfs2_ail_empty_gl() would catch that case as well.

    Signed-off-by: Benjamin E. Marzinski <bmarzins@redhat.com>
    Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

    diff --git a/fs/gfs2/glops.c b/fs/gfs2/glops.c
    index 7b82657..777ca46 100644
    --- a/fs/gfs2/glops.c
    +++ b/fs/gfs2/glops.c
    @@ -156,9 +156,9 @@ static void inode_go_sync(struct gfs2_glock *gl)
    ip = NULL;

    if (test_bit(GLF_DIRTY, &gl->gl_flags)) {
    - gfs2_log_flush(gl->gl_sbd, gl);
    if (ip)
    filemap_fdatawrite(ip->i_inode.i_mapping);
    + gfs2_log_flush(gl->gl_sbd, gl);
    gfs2_meta_sync(gl);
    if (ip) {
    struct address_space *mapping = ip->i_inode.i_mapping;
    --
    1.5.1.2
    -
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