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    Subject[PATCH 50/58] [GFS2] Fix assert in log code
    Date
    From: Steven Whitehouse <swhiteho@redhat.com>

    Although the values were all being calculated correctly, there was a
    race in the assert due to the way it was using atomic variables. This
    changes the value we assert on so that we get the same effect by testing
    a different variable. This prevents the assert triggering when it shouldn't.

    Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

    diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
    index 40c51bf..6e6a104 100644
    --- a/fs/gfs2/log.c
    +++ b/fs/gfs2/log.c
    @@ -749,7 +749,7 @@ void __gfs2_log_flush(struct gfs2_sbd *sdp, struct gfs2_glock *gl)
    static void log_refund(struct gfs2_sbd *sdp, struct gfs2_trans *tr)
    {
    unsigned int reserved;
    - unsigned int old;
    + unsigned int unused;

    gfs2_log_lock(sdp);

    @@ -761,14 +761,11 @@ static void log_refund(struct gfs2_sbd *sdp, struct gfs2_trans *tr)
    sdp->sd_log_commited_revoke += tr->tr_num_revoke - tr->tr_num_revoke_rm;
    gfs2_assert_withdraw(sdp, ((int)sdp->sd_log_commited_revoke) >= 0);
    reserved = calc_reserved(sdp);
    - old = atomic_read(&sdp->sd_log_blks_free);
    - atomic_add(tr->tr_reserved - (reserved - sdp->sd_log_blks_reserved),
    - &sdp->sd_log_blks_free);
    -
    - gfs2_assert_withdraw(sdp, atomic_read(&sdp->sd_log_blks_free) >= old);
    + unused = sdp->sd_log_blks_reserved - reserved + tr->tr_reserved;
    + gfs2_assert_withdraw(sdp, unused >= 0);
    + atomic_add(unused, &sdp->sd_log_blks_free);
    gfs2_assert_withdraw(sdp, atomic_read(&sdp->sd_log_blks_free) <=
    sdp->sd_jdesc->jd_blocks);
    -
    sdp->sd_log_blks_reserved = reserved;

    gfs2_log_unlock(sdp);
    --
    1.5.1.2


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