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Subject[PATCH 11/12] GFS2: Clean up log flush header writing
Date
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>

diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index 2b9f0d9..4752ead 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);
--
1.7.4


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