gfs2: allow journal replay to hold sd_log_flush_lock

Before this patch, journal replays could stomp on log flushes
and each other because both log flushes and journal replays used
the same sd_log_bio. Function gfs2_log_flush prevents other log
flushes from interfering by taking the sd_log_flush_lock rwsem
during the flush. However, it does not protect against journal
replays. This patch allows the journal replay to take the same
sd_log_flush_lock rwsem so use of the sd_log_bio is not stomped.

Signed-off-by: Bob Peterson <rpeterso@redhat.com>

diff --git a/fs/gfs2/recovery.c b/fs/gfs2/recovery.c
index 8cc26be..21fc44b 100644 (file)
--- a/fs/gfs2/recovery.c
+++ b/fs/gfs2/recovery.c
@@ -398,6 +398,10 @@ void gfs2_recover_func(struct work_struct *work)
                fs_info(sdp, "jid=%u: Replaying journal...0x%x to 0x%x\n",
                        jd->jd_jid, head.lh_tail, head.lh_blkno);
 
+               /* We take the sd_log_flush_lock here primarily to prevent log
+                * flushes and simultaneous journal replays from stomping on
+                * each other wrt sd_log_bio. */
+               down_write(&sdp->sd_log_flush_lock);
                for (pass = 0; pass < 2; pass++) {
                        lops_before_scan(jd, &head, pass);
                        error = foreach_descriptor(jd, head.lh_tail,
@@ -408,6 +412,7 @@ void gfs2_recover_func(struct work_struct *work)
                }
 
                clean_journal(jd, &head);
+               up_write(&sdp->sd_log_flush_lock);
 
                gfs2_glock_dq_uninit(&thaw_gh);
                t_rep = ktime_get();