[Cluster-devel] [PATCH] GFS2: aggressively issue revokes in gfs2_log_flush

[Benjamin Marzinski]

This patch looks at all the outstanding blocks in all the transactions
on the log, and moves the completed ones to the ail2 list.  Then it
issues revokes for these blocks.  This will hopefully speed things up
in situations where there is a lot of contention for glocks, especially
if they are acquired serially.

revoke_lo_before_commit will issue at most one log block's full of these
preemptive revokes. The amount of reserved log space that
gfs2_log_reserve() ignores has been incremented to allow for this extra
block.

Signed-off-by: Benjamin Marzinski <bmarzins at redhat.com>
---
 fs/gfs2/log.c  |   74 +++++++++++++++++++++++++++++++++++++++++++++++++++++----
 fs/gfs2/log.h  |    1 
 fs/gfs2/lops.c |    1 
 3 files changed, 72 insertions(+), 4 deletions(-)

Index: gfs2-3.0-nmw-130611/fs/gfs2/log.c
===================================================================
--- gfs2-3.0-nmw-130611.orig/fs/gfs2/log.c
+++ gfs2-3.0-nmw-130611/fs/gfs2/log.c
@@ -211,15 +211,16 @@ static void gfs2_ail1_empty_one(struct g
 static int gfs2_ail1_empty(struct gfs2_sbd *sdp)
 {
 	struct gfs2_trans *tr, *s;
+	int oldest_tr = 1;
 	int ret;
 
 	spin_lock(&sdp->sd_ail_lock);
 	list_for_each_entry_safe_reverse(tr, s, &sdp->sd_ail1_list, tr_list) {
 		gfs2_ail1_empty_one(sdp, tr);
-		if (list_empty(&tr->tr_ail1_list))
+		if (list_empty(&tr->tr_ail1_list) && oldest_tr)
 			list_move(&tr->tr_list, &sdp->sd_ail2_list);
 		else
-			break;
+			oldest_tr = 0;
 	}
 	ret = list_empty(&sdp->sd_ail1_list);
 	spin_unlock(&sdp->sd_ail_lock);
@@ -317,7 +318,7 @@ static void ail2_empty(struct gfs2_sbd *
 
 int gfs2_log_reserve(struct gfs2_sbd *sdp, unsigned int blks)
 {
-	unsigned reserved_blks = 6 * (4096 / sdp->sd_vfs->s_blocksize);
+	unsigned reserved_blks = 7 * (4096 / sdp->sd_vfs->s_blocksize);
 	unsigned wanted = blks + reserved_blks;
 	DEFINE_WAIT(wait);
 	int did_wait = 0;
@@ -545,6 +546,72 @@ void gfs2_ordered_del_inode(struct gfs2_
 	spin_unlock(&sdp->sd_ordered_lock);
 }
 
+void write_revokes(struct gfs2_sbd *sdp)
+{
+	struct gfs2_trans *tr;
+	struct gfs2_bufdata *bd, *tmp;
+	struct buffer_head *bh;
+	struct gfs2_glock *gl;
+	int have_revokes = 0;
+	int max_revokes = (sdp->sd_sb.sb_bsize - sizeof(struct gfs2_log_descriptor)) / sizeof(u64);
+
+	gfs2_ail1_empty(sdp);
+	spin_lock(&sdp->sd_ail_lock);
+	list_for_each_entry(tr, &sdp->sd_ail1_list, tr_list) {
+		list_for_each_entry(bd, &tr->tr_ail2_list, bd_ail_st_list) {
+			if (list_empty(&bd->bd_list)) {
+				have_revokes = 1;
+				goto done;
+			}
+		}
+	}
+done:
+	spin_unlock(&sdp->sd_ail_lock);
+	if (have_revokes == 0)
+		return;
+	while (sdp->sd_log_num_revoke > max_revokes)
+		max_revokes += (sdp->sd_sb.sb_bsize - sizeof(struct gfs2_meta_header)) / sizeof(u64);
+	max_revokes -= sdp->sd_log_num_revoke;
+	if (!sdp->sd_log_num_revoke) {
+		atomic_dec(&sdp->sd_log_blks_free);
+		/* If no blocks have been reserved, we need to also
+		 * reserve a block for the header */
+		if (!sdp->sd_log_blks_reserved)
+			atomic_dec(&sdp->sd_log_blks_free);
+	}
+	gfs2_log_lock(sdp);
+	spin_lock(&sdp->sd_ail_lock);
+	list_for_each_entry(tr, &sdp->sd_ail1_list, tr_list) {
+		list_for_each_entry_safe(bd, tmp, &tr->tr_ail2_list, bd_ail_st_list) {
+			if (max_revokes == 0)
+				goto out_of_blocks;
+			if (!list_empty(&bd->bd_list))
+				continue;
+			gl = bd->bd_gl;
+			bh = bd->bd_bh;
+			bd->bd_blkno = bh->b_blocknr;
+			bh->b_private = NULL;
+			gfs2_remove_from_ail(bd);
+			bd->bd_bh = NULL;
+			bd->bd_ops = &gfs2_revoke_lops;
+			sdp->sd_log_num_revoke++;
+			atomic_inc(&gl->gl_revokes);
+			set_bit(GLF_LFLUSH, &gl->gl_flags);
+			list_add_tail(&bd->bd_list, &sdp->sd_log_le_revoke);
+			max_revokes--;
+		}
+	}
+out_of_blocks:
+	spin_unlock(&sdp->sd_ail_lock);
+	gfs2_log_unlock(sdp);
+
+	if (!sdp->sd_log_num_revoke) {
+		atomic_inc(&sdp->sd_log_blks_free);
+		if (!sdp->sd_log_blks_reserved)
+			atomic_inc(&sdp->sd_log_blks_free);
+	}
+}
+
 /**
  * log_write_header - Get and initialize a journal header buffer
  * @sdp: The GFS2 superblock
@@ -562,7 +629,6 @@ static void log_write_header(struct gfs2
 	lh = page_address(page);
 	clear_page(lh);
 
-	gfs2_ail1_empty(sdp);
 	tail = current_tail(sdp);
 
 	lh->lh_header.mh_magic = cpu_to_be32(GFS2_MAGIC);
Index: gfs2-3.0-nmw-130611/fs/gfs2/log.h
===================================================================
--- gfs2-3.0-nmw-130611.orig/fs/gfs2/log.h
+++ gfs2-3.0-nmw-130611/fs/gfs2/log.h
@@ -72,5 +72,6 @@ extern void gfs2_ail1_flush(struct gfs2_
 extern void gfs2_log_shutdown(struct gfs2_sbd *sdp);
 extern void gfs2_meta_syncfs(struct gfs2_sbd *sdp);
 extern int gfs2_logd(void *data);
+extern void write_revokes(struct gfs2_sbd *sdp);
 
 #endif /* __LOG_DOT_H__ */
Index: gfs2-3.0-nmw-130611/fs/gfs2/lops.c
===================================================================
--- gfs2-3.0-nmw-130611.orig/fs/gfs2/lops.c
+++ gfs2-3.0-nmw-130611/fs/gfs2/lops.c
@@ -606,6 +606,7 @@ static void revoke_lo_before_commit(stru
 	struct page *page;
 	unsigned int length;
 
+	write_revokes(sdp);
 	if (!sdp->sd_log_num_revoke)
 		return;