GFS2: Clean up log flush header writing

We already send both a pre and post flush to the block device
when writing a journal header. There is no need to wait for
the previous I/O specifically when we do this, unless we've
turned "barriers" off.

As a side effect, this also cleans up the code path for flushing
the journal and makes it more readable.

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

1 files changed, 66 insertions, 65 deletions

diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index 2b9f0d9b1b28..4752eadc7f6e 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -491,66 +491,8 @@ static void log_pull_tail(struct gfs2_sbd *sdp, unsigned int new_tail)
         sdp->sd_log_tail = new_tail;
 }
 
-/**
- * log_write_header - Get and initialize a journal header buffer
- * @sdp: The GFS2 superblock
- *
- * Returns: the initialized log buffer descriptor
- */
 
-static void log_write_header(struct gfs2_sbd *sdp, u32 flags, int pull)
-{
-        u64 blkno = gfs2_log_bmap(sdp, sdp->sd_log_flush_head);
-        struct buffer_head *bh;
-        struct gfs2_log_header *lh;
-        unsigned int tail;
-        u32 hash;
-
-        bh = sb_getblk(sdp->sd_vfs, blkno);
-        lock_buffer(bh);
-        memset(bh->b_data, 0, bh->b_size);
-        set_buffer_uptodate(bh);
-        clear_buffer_dirty(bh);
-
-        gfs2_ail1_empty(sdp);
-        tail = current_tail(sdp);
-
-        lh = (struct gfs2_log_header *)bh->b_data;
-        memset(lh, 0, sizeof(struct gfs2_log_header));
-        lh->lh_header.mh_magic = cpu_to_be32(GFS2_MAGIC);
-        lh->lh_header.mh_type = cpu_to_be32(GFS2_METATYPE_LH);
-        lh->lh_header.__pad0 = cpu_to_be64(0);
-        lh->lh_header.mh_format = cpu_to_be32(GFS2_FORMAT_LH);
-        lh->lh_header.mh_jid = cpu_to_be32(sdp->sd_jdesc->jd_jid);
-        lh->lh_sequence = cpu_to_be64(sdp->sd_log_sequence++);
-        lh->lh_flags = cpu_to_be32(flags);
-        lh->lh_tail = cpu_to_be32(tail);
-        lh->lh_blkno = cpu_to_be32(sdp->sd_log_flush_head);
-        hash = gfs2_disk_hash(bh->b_data, sizeof(struct gfs2_log_header));
-        lh->lh_hash = cpu_to_be32(hash);
-
-        bh->b_end_io = end_buffer_write_sync;
-        get_bh(bh);
-        if (test_bit(SDF_NOBARRIERS, &sdp->sd_flags))
-                submit_bh(WRITE_SYNC | REQ_META | REQ_PRIO, bh);
-        else
-                submit_bh(WRITE_FLUSH_FUA | REQ_META, bh);
-        wait_on_buffer(bh);
-
-        if (!buffer_uptodate(bh))
-                gfs2_io_error_bh(sdp, bh);
-        brelse(bh);
-
-        if (sdp->sd_log_tail != tail)
-                log_pull_tail(sdp, tail);
-        else
-                gfs2_assert_withdraw(sdp, !pull);
-
-        sdp->sd_log_idle = (tail == sdp->sd_log_flush_head);
-        gfs2_log_incr_head(sdp);
-}
-
-static void log_flush_commit(struct gfs2_sbd *sdp)
+static void log_flush_wait(struct gfs2_sbd *sdp)
 {
         DEFINE_WAIT(wait);
 
@@ -563,8 +505,6 @@ static void log_flush_commit(struct gfs2_sbd *sdp)
                 } while(atomic_read(&sdp->sd_log_in_flight));
                 finish_wait(&sdp->sd_log_flush_wait, &wait);
         }
-
-        log_write_header(sdp, 0, 0);
 }
 
 static int bd_cmp(void *priv, struct list_head *a, struct list_head *b)
@@ -634,6 +574,68 @@ static void gfs2_ordered_wait(struct gfs2_sbd *sdp)
 }
 
 /**
+ * log_write_header - Get and initialize a journal header buffer
+ * @sdp: The GFS2 superblock
+ *
+ * Returns: the initialized log buffer descriptor
+ */
+
+static void log_write_header(struct gfs2_sbd *sdp, u32 flags, int pull)
+{
+        u64 blkno = gfs2_log_bmap(sdp, sdp->sd_log_flush_head);
+        struct buffer_head *bh;
+        struct gfs2_log_header *lh;
+        unsigned int tail;
+        u32 hash;
+
+        bh = sb_getblk(sdp->sd_vfs, blkno);
+        lock_buffer(bh);
+        memset(bh->b_data, 0, bh->b_size);
+        set_buffer_uptodate(bh);
+        clear_buffer_dirty(bh);
+
+        gfs2_ail1_empty(sdp);
+        tail = current_tail(sdp);
+
+        lh = (struct gfs2_log_header *)bh->b_data;
+        memset(lh, 0, sizeof(struct gfs2_log_header));
+        lh->lh_header.mh_magic = cpu_to_be32(GFS2_MAGIC);
+        lh->lh_header.mh_type = cpu_to_be32(GFS2_METATYPE_LH);
+        lh->lh_header.__pad0 = cpu_to_be64(0);
+        lh->lh_header.mh_format = cpu_to_be32(GFS2_FORMAT_LH);
+        lh->lh_header.mh_jid = cpu_to_be32(sdp->sd_jdesc->jd_jid);
+        lh->lh_sequence = cpu_to_be64(sdp->sd_log_sequence++);
+        lh->lh_flags = cpu_to_be32(flags);
+        lh->lh_tail = cpu_to_be32(tail);
+        lh->lh_blkno = cpu_to_be32(sdp->sd_log_flush_head);
+        hash = gfs2_disk_hash(bh->b_data, sizeof(struct gfs2_log_header));
+        lh->lh_hash = cpu_to_be32(hash);
+
+        bh->b_end_io = end_buffer_write_sync;
+        get_bh(bh);
+        if (test_bit(SDF_NOBARRIERS, &sdp->sd_flags)) {
+                gfs2_ordered_wait(sdp);
+                log_flush_wait(sdp);
+                submit_bh(WRITE_SYNC | REQ_META | REQ_PRIO, bh);
+        } else {
+                submit_bh(WRITE_FLUSH_FUA | REQ_META, bh);
+        }
+        wait_on_buffer(bh);
+
+        if (!buffer_uptodate(bh))
+                gfs2_io_error_bh(sdp, bh);
+        brelse(bh);
+
+        if (sdp->sd_log_tail != tail)
+                log_pull_tail(sdp, tail);
+        else
+                gfs2_assert_withdraw(sdp, !pull);
+
+        sdp->sd_log_idle = (tail == sdp->sd_log_flush_head);
+        gfs2_log_incr_head(sdp);
+}
+
+/**
  * gfs2_log_flush - flush incore transaction(s)
  * @sdp: the filesystem
  * @gl: The glock structure to flush.  If NULL, flush the whole incore log
@@ -676,11 +678,10 @@ void gfs2_log_flush(struct gfs2_sbd *sdp, struct gfs2_glock *gl)
 
         gfs2_ordered_write(sdp);
         lops_before_commit(sdp);
-        gfs2_ordered_wait(sdp);
 
-        if (sdp->sd_log_head != sdp->sd_log_flush_head)
-                log_flush_commit(sdp);
-        else if (sdp->sd_log_tail != current_tail(sdp) && !sdp->sd_log_idle){
+        if (sdp->sd_log_head != sdp->sd_log_flush_head) {
+                log_write_header(sdp, 0, 0);
+        } else if (sdp->sd_log_tail != current_tail(sdp) && !sdp->sd_log_idle){
                 gfs2_log_lock(sdp);
                 atomic_dec(&sdp->sd_log_blks_free); /* Adjust for unreserved buffer */
                 trace_gfs2_log_blocks(sdp, -1);