[Cluster-devel] [PATCH v3 00/20] Some log space management cleanups

[Cluster-devel] [PATCH v3 00/20] Some log space management cleanups

[Andreas Gruenbacher]

Hello,

here's another update on the log log space management cleanup.  The
changes are mostly in the topmost patch ("gfs2: Per-revoke accounting in
transactions"), which still had several bugs in v2.  Please review.

Thanks,
Andreas

Andreas Gruenbacher (20):
  gfs2: Un-obfuscate function jdesc_find_i
  gfs2: Simplify the buf_limit and databuf_limit definitions
  gfs2: Minor gfs2_write_revokes cleanups
  gfs2: Some documentation updates
  gfs2: Minor debugging improvement
  gfs2: Rename gfs2_{write => flush}_revokes
  gfs2: Clean up ail2_empty
  gfs2: Get rid of on-stack transactions
  gfs2: Get rid of sd_reserving_log
  gfs2: Move lock flush locking to gfs2_trans_{begin,end}
  gfs2: Don't wait for journal flush in clean_journal
  gfs2: Clean up gfs2_log_reserve
  gfs2: Use a tighter bound in gfs2_trans_begin
  gfs2: Get rid of current_tail()
  gfs2: Move function gfs2_ail_empty_tr
  gfs2: No revokes for transactions at the tail of the log
  gfs2: Remove sd_log_committed_revoke
  gfs2: Remove sd_log_blks_reserved
  gfs2: Rework the log space allocation logic
  gfs2: Per-revoke accounting in transactions

 fs/gfs2/glops.c      |  37 +--
 fs/gfs2/incore.h     |  13 +-
 fs/gfs2/log.c        | 545 +++++++++++++++++++++++++------------------
 fs/gfs2/log.h        |  20 +-
 fs/gfs2/lops.c       |   3 +-
 fs/gfs2/lops.h       |  17 +-
 fs/gfs2/ops_fstype.c |   9 +-
 fs/gfs2/super.c      |  25 +-
 fs/gfs2/trans.c      |  89 ++++---
 fs/gfs2/trans.h      |   2 +
 10 files changed, 426 insertions(+), 334 deletions(-)

-- 
2.26.2

[Cluster-devel] [PATCH v3 01/20] gfs2: Un-obfuscate function jdesc_find_i

[Andreas Gruenbacher]

Clean up this function to show that it is trivial.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
 fs/gfs2/super.c | 13 +++----------
 1 file changed, 3 insertions(+), 10 deletions(-)

diff --git a/fs/gfs2/super.c b/fs/gfs2/super.c
index 2f56acc41c04..ed7a829e9ffe 100644
--- a/fs/gfs2/super.c
+++ b/fs/gfs2/super.c
@@ -81,19 +81,12 @@ void gfs2_jindex_free(struct gfs2_sbd *sdp)
 static struct gfs2_jdesc *jdesc_find_i(struct list_head *head, unsigned int jid)
 {
 	struct gfs2_jdesc *jd;
-	int found = 0;
 
 	list_for_each_entry(jd, head, jd_list) {
-		if (jd->jd_jid == jid) {
-			found = 1;
-			break;
-		}
+		if (jd->jd_jid == jid)
+			return jd;
 	}
-
-	if (!found)
-		jd = NULL;
-
-	return jd;
+	return NULL;
 }
 
 struct gfs2_jdesc *gfs2_jdesc_find(struct gfs2_sbd *sdp, unsigned int jid)
-- 
2.26.2

[Cluster-devel] [PATCH v3 02/20] gfs2: Simplify the buf_limit and databuf_limit definitions

[Andreas Gruenbacher]

The BUF_OFFSET and DATABUF_OFFSET definitions are only used in buf_limit
and databuf_limit, respectively, and the rounding done in those
definitions is immediately wiped out by dividing by the element size.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
 fs/gfs2/lops.h | 17 ++---------------
 1 file changed, 2 insertions(+), 15 deletions(-)

diff --git a/fs/gfs2/lops.h b/fs/gfs2/lops.h
index fbdbb08dcec6..3fca5bf239d3 100644
--- a/fs/gfs2/lops.h
+++ b/fs/gfs2/lops.h
@@ -10,13 +10,6 @@
 #include <linux/list.h>
 #include "incore.h"
 
-#define BUF_OFFSET \
-	((sizeof(struct gfs2_log_descriptor) + sizeof(__be64) - 1) & \
-	 ~(sizeof(__be64) - 1))
-#define DATABUF_OFFSET \
-	((sizeof(struct gfs2_log_descriptor) + (2 * sizeof(__be64) - 1)) & \
-	 ~(2 * sizeof(__be64) - 1))
-
 extern const struct gfs2_log_operations *gfs2_log_ops[];
 extern void gfs2_log_incr_head(struct gfs2_sbd *sdp);
 extern u64 gfs2_log_bmap(struct gfs2_jdesc *jd, unsigned int lbn);
@@ -29,18 +22,12 @@ extern int gfs2_find_jhead(struct gfs2_jdesc *jd,
 			   struct gfs2_log_header_host *head, bool keep_cache);
 static inline unsigned int buf_limit(struct gfs2_sbd *sdp)
 {
-	unsigned int limit;
-
-	limit = (sdp->sd_sb.sb_bsize - BUF_OFFSET) / sizeof(__be64);
-	return limit;
+	return sdp->sd_ldptrs;
 }
 
 static inline unsigned int databuf_limit(struct gfs2_sbd *sdp)
 {
-	unsigned int limit;
-
-	limit = (sdp->sd_sb.sb_bsize - DATABUF_OFFSET) / (2 * sizeof(__be64));
-	return limit;
+	return sdp->sd_ldptrs / 2;
 }
 
 static inline void lops_before_commit(struct gfs2_sbd *sdp,
-- 
2.26.2

[Cluster-devel] [PATCH v3 03/20] gfs2: Minor gfs2_write_revokes cleanups

[Andreas Gruenbacher]

Clean up the computations in gfs2_write_revokes (no change in functionality).

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
 fs/gfs2/log.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index 2e9314091c81..ccce17fe605f 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -712,11 +712,13 @@ void gfs2_glock_remove_revoke(struct gfs2_glock *gl)
 void gfs2_write_revokes(struct gfs2_sbd *sdp)
 {
 	/* number of revokes we still have room for */
-	int max_revokes = (sdp->sd_sb.sb_bsize - sizeof(struct gfs2_log_descriptor)) / sizeof(u64);
+	unsigned int max_revokes;
 
 	gfs2_log_lock(sdp);
-	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_ldptrs;
+	if (sdp->sd_log_num_revoke > sdp->sd_ldptrs)
+		max_revokes += roundup(sdp->sd_log_num_revoke - sdp->sd_ldptrs,
+				       sdp->sd_inptrs);
 	max_revokes -= sdp->sd_log_num_revoke;
 	if (!sdp->sd_log_num_revoke) {
 		atomic_dec(&sdp->sd_log_blks_free);
-- 
2.26.2

[Cluster-devel] [PATCH v3 04/20] gfs2: Some documentation updates

[Andreas Gruenbacher]

The calc_reserved description claims that buf_limit is 502 (on 4k
filesystems), but it is actually 503.  Fix / clarify the entire
description.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
 fs/gfs2/log.c | 24 +++++++++++-------------
 1 file changed, 11 insertions(+), 13 deletions(-)

diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index ccce17fe605f..12e8280f0806 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -50,10 +50,12 @@ unsigned int gfs2_struct2blk(struct gfs2_sbd *sdp, unsigned int nstruct)
 	unsigned int blks;
 	unsigned int first, second;
 
+	/* The initial struct gfs2_log_descriptor block */
 	blks = 1;
 	first = sdp->sd_ldptrs;
 
 	if (nstruct > first) {
+		/* Subsequent struct gfs2_meta_header blocks */
 		second = sdp->sd_inptrs;
 		blks += DIV_ROUND_UP(nstruct - first, second);
 	}
@@ -507,24 +509,20 @@ static inline unsigned int log_distance(struct gfs2_sbd *sdp, unsigned int newer
 }
 
 /**
- * calc_reserved - Calculate the number of blocks to reserve when
- *                 refunding a transaction's unused buffers.
+ * calc_reserved - Calculate the number of blocks to keep reserved
  * @sdp: The GFS2 superblock
  *
  * This is complex.  We need to reserve room for all our currently used
- * metadata buffers (e.g. normal file I/O rewriting file time stamps) and 
- * all our journaled data buffers for journaled files (e.g. files in the 
+ * metadata blocks (e.g. normal file I/O rewriting file time stamps) and
+ * all our journaled data blocks for journaled files (e.g. files in the
  * meta_fs like rindex, or files for which chattr +j was done.)
- * If we don't reserve enough space, gfs2_log_refund and gfs2_log_flush
- * will count it as free space (sd_log_blks_free) and corruption will follow.
+ * If we don't reserve enough space, corruption will follow.
  *
- * We can have metadata bufs and jdata bufs in the same journal.  So each
- * type gets its own log header, for which we need to reserve a block.
- * In fact, each type has the potential for needing more than one header 
- * in cases where we have more buffers than will fit on a journal page.
+ * We can have metadata blocks and jdata blocks in the same journal.  Each
+ * type gets its own log descriptor, for which we need to reserve a block.
+ * In fact, each type has the potential for needing more than one log descriptor
+ * in cases where we have more blocks than will fit in a log descriptor.
  * Metadata journal entries take up half the space of journaled buffer entries.
- * Thus, metadata entries have buf_limit (502) and journaled buffers have
- * databuf_limit (251) before they cause a wrap around.
  *
  * Also, we need to reserve blocks for revoke journal entries and one for an
  * overall header for the lot.
@@ -1008,7 +1006,7 @@ void gfs2_log_flush(struct gfs2_sbd *sdp, struct gfs2_glock *gl, u32 flags)
 	if (sdp->sd_log_head != sdp->sd_log_flush_head) {
 		log_flush_wait(sdp);
 		log_write_header(sdp, flags);
-	} else if (sdp->sd_log_tail != current_tail(sdp) && !sdp->sd_log_idle){
+	} else if (sdp->sd_log_tail != current_tail(sdp) && !sdp->sd_log_idle) {
 		atomic_dec(&sdp->sd_log_blks_free); /* Adjust for unreserved buffer */
 		trace_gfs2_log_blocks(sdp, -1);
 		log_write_header(sdp, flags);
-- 
2.26.2

[Cluster-devel] [PATCH v3 05/20] gfs2: Minor debugging improvement

[Andreas Gruenbacher]

Split the assert in gfs2_trans_end into two parts.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
 fs/gfs2/trans.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/gfs2/trans.c b/fs/gfs2/trans.c
index 6d4bf7ea7b3b..7705f04621f4 100644
--- a/fs/gfs2/trans.c
+++ b/fs/gfs2/trans.c
@@ -109,8 +109,8 @@ void gfs2_trans_end(struct gfs2_sbd *sdp)
 	nbuf -= tr->tr_num_buf_rm;
 	nbuf -= tr->tr_num_databuf_rm;
 
-	if (gfs2_assert_withdraw(sdp, (nbuf <= tr->tr_blocks) &&
-				       (tr->tr_num_revoke <= tr->tr_revokes)))
+	if (gfs2_assert_withdraw(sdp, nbuf <= tr->tr_blocks) ||
+	    gfs2_assert_withdraw(sdp, tr->tr_num_revoke <= tr->tr_revokes))
 		gfs2_print_trans(sdp, tr);
 
 	gfs2_log_commit(sdp, tr);
-- 
2.26.2

[Cluster-devel] [PATCH v3 06/20] gfs2: Rename gfs2_{write => flush}_revokes

[Andreas Gruenbacher]

Function gfs2_write_revokes doesn't actually write any revokes; instead, it
adds revokes to the system transaction during a flush.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
 fs/gfs2/log.c  | 4 ++--
 fs/gfs2/log.h  | 2 +-
 fs/gfs2/lops.c | 2 +-
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index 12e8280f0806..7375c007bde5 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -696,7 +696,7 @@ void gfs2_glock_remove_revoke(struct gfs2_glock *gl)
 }
 
 /**
- * gfs2_write_revokes - Add as many revokes to the system transaction as we can
+ * gfs2_flush_revokes - Add as many revokes to the system transaction as we can
  * @sdp: The GFS2 superblock
  *
  * Our usual strategy is to defer writing revokes as much as we can in the hope
@@ -707,7 +707,7 @@ void gfs2_glock_remove_revoke(struct gfs2_glock *gl)
  * been written back.  This will basically come at no cost now, and will save
  * us from having to keep track of those blocks on the AIL2 list later.
  */
-void gfs2_write_revokes(struct gfs2_sbd *sdp)
+void gfs2_flush_revokes(struct gfs2_sbd *sdp)
 {
 	/* number of revokes we still have room for */
 	unsigned int max_revokes;
diff --git a/fs/gfs2/log.h b/fs/gfs2/log.h
index 79f97290146e..a9cdbc990edf 100644
--- a/fs/gfs2/log.h
+++ b/fs/gfs2/log.h
@@ -78,6 +78,6 @@ extern void log_flush_wait(struct gfs2_sbd *sdp);
 extern int gfs2_logd(void *data);
 extern void gfs2_add_revoke(struct gfs2_sbd *sdp, struct gfs2_bufdata *bd);
 extern void gfs2_glock_remove_revoke(struct gfs2_glock *gl);
-extern void gfs2_write_revokes(struct gfs2_sbd *sdp);
+extern void gfs2_flush_revokes(struct gfs2_sbd *sdp);
 
 #endif /* __LOG_DOT_H__ */
diff --git a/fs/gfs2/lops.c b/fs/gfs2/lops.c
index 3922b26264f5..8658ebbcb4a9 100644
--- a/fs/gfs2/lops.c
+++ b/fs/gfs2/lops.c
@@ -845,7 +845,7 @@ static void revoke_lo_before_commit(struct gfs2_sbd *sdp, struct gfs2_trans *tr)
 	struct page *page;
 	unsigned int length;
 
-	gfs2_write_revokes(sdp);
+	gfs2_flush_revokes(sdp);
 	if (!sdp->sd_log_num_revoke)
 		return;
 
-- 
2.26.2

[Cluster-devel] [PATCH v3 07/20] gfs2: Clean up ail2_empty

[Andreas Gruenbacher]

Clean up the logic in ail2_empty (no functional change).

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
 fs/gfs2/log.c | 38 +++++++++++++++++++++-----------------
 1 file changed, 21 insertions(+), 17 deletions(-)

diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index 7375c007bde5..e4dc23a24569 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -367,29 +367,33 @@ static void gfs2_ail_empty_tr(struct gfs2_sbd *sdp, struct gfs2_trans *tr,
 	}
 }
 
+static void __ail2_empty(struct gfs2_sbd *sdp, struct gfs2_trans *tr)
+{
+	gfs2_ail_empty_tr(sdp, tr, &tr->tr_ail2_list);
+	list_del(&tr->tr_list);
+	gfs2_assert_warn(sdp, list_empty(&tr->tr_ail1_list));
+	gfs2_assert_warn(sdp, list_empty(&tr->tr_ail2_list));
+	gfs2_trans_free(sdp, tr);
+}
+
 static void ail2_empty(struct gfs2_sbd *sdp, unsigned int new_tail)
 {
-	struct gfs2_trans *tr, *safe;
+	struct list_head *ail2_list = &sdp->sd_ail2_list;
 	unsigned int old_tail = sdp->sd_log_tail;
-	int wrap = (new_tail < old_tail);
-	int a, b, rm;
+	struct gfs2_trans *tr, *safe;
 
 	spin_lock(&sdp->sd_ail_lock);
-
-	list_for_each_entry_safe(tr, safe, &sdp->sd_ail2_list, tr_list) {
-		a = (old_tail <= tr->tr_first);
-		b = (tr->tr_first < new_tail);
-		rm = (wrap) ? (a || b) : (a && b);
-		if (!rm)
-			continue;
-
-		gfs2_ail_empty_tr(sdp, tr, &tr->tr_ail2_list);
-		list_del(&tr->tr_list);
-		gfs2_assert_warn(sdp, list_empty(&tr->tr_ail1_list));
-		gfs2_assert_warn(sdp, list_empty(&tr->tr_ail2_list));
-		gfs2_trans_free(sdp, tr);
+	if (old_tail <= new_tail) {
+		list_for_each_entry_safe(tr, safe, ail2_list, tr_list) {
+			if (old_tail <= tr->tr_first && tr->tr_first < new_tail)
+				__ail2_empty(sdp, tr);
+		}
+	} else {
+		list_for_each_entry_safe(tr, safe, ail2_list, tr_list) {
+			if (old_tail <= tr->tr_first || tr->tr_first < new_tail)
+				__ail2_empty(sdp, tr);
+		}
 	}
-
 	spin_unlock(&sdp->sd_ail_lock);
 }
 
-- 
2.26.2

[Cluster-devel] [PATCH v3 08/20] gfs2: Get rid of on-stack transactions

[Andreas Gruenbacher]

On-stack transactions were introduced to work around a transaction glock
deadlock in gfs2_trans_begin in commit d8348de06f70 ("GFS2: Fix deadlock
on journal flush").  Subsequently, transaction glocks were eliminated in
favor of the more efficient freeze glocks in commit 24972557b12c ("GFS2:
remove transaction glock") without also removing the on-stack
transactions.

It has now turned out that committing on-stack transactions
significantly complicates journal free space accounting when no system
transaction (sdp->sd_log_tr) is active at the time.  It doesn't seem
that on-stack transactions provide a significant benefit beyond their
original purpose (as an optimization), so remove them to allow fixing
the journal free space accounting in a reasonable way in a subsequent
patch.

FIXME: Can we better handle a gfs2_trans_begin failure in gfs2_ail_empty_gl?
If we skip the __gfs2_ail_flush, we'll just end up with leftover items on
gl_ail_list.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
 fs/gfs2/glops.c  | 29 +++++++----------------------
 fs/gfs2/incore.h |  1 -
 fs/gfs2/log.c    |  1 -
 fs/gfs2/trans.c  | 25 +++++++++++++------------
 fs/gfs2/trans.h  |  2 ++
 5 files changed, 22 insertions(+), 36 deletions(-)

diff --git a/fs/gfs2/glops.c b/fs/gfs2/glops.c
index 3faa421568b0..853e590ccc15 100644
--- a/fs/gfs2/glops.c
+++ b/fs/gfs2/glops.c
@@ -84,18 +84,11 @@ static void __gfs2_ail_flush(struct gfs2_glock *gl, bool fsync,
 
 static int gfs2_ail_empty_gl(struct gfs2_glock *gl)
 {
+	unsigned int revokes = atomic_read(&gl->gl_ail_count);
 	struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
-	struct gfs2_trans tr;
 	int ret;
 
-	memset(&tr, 0, sizeof(tr));
-	INIT_LIST_HEAD(&tr.tr_buf);
-	INIT_LIST_HEAD(&tr.tr_databuf);
-	INIT_LIST_HEAD(&tr.tr_ail1_list);
-	INIT_LIST_HEAD(&tr.tr_ail2_list);
-	tr.tr_revokes = atomic_read(&gl->gl_ail_count);
-
-	if (!tr.tr_revokes) {
+	if (!revokes) {
 		bool have_revokes;
 		bool log_in_flight;
 
@@ -122,20 +115,12 @@ static int gfs2_ail_empty_gl(struct gfs2_glock *gl)
 		return 0;
 	}
 
-	/* A shortened, inline version of gfs2_trans_begin()
-         * tr->alloced is not set since the transaction structure is
-         * on the stack */
-	tr.tr_reserved = 1 + gfs2_struct2blk(sdp, tr.tr_revokes);
-	tr.tr_ip = _RET_IP_;
-	ret = gfs2_log_reserve(sdp, tr.tr_reserved);
-	if (ret < 0)
-		return ret;
-	WARN_ON_ONCE(current->journal_info);
-	current->journal_info = &tr;
-
-	__gfs2_ail_flush(gl, 0, tr.tr_revokes);
-
+	ret = __gfs2_trans_begin(sdp, 0, revokes, GFP_NOFS | __GFP_NOFAIL);
+	if (ret)
+		goto flush;
+	__gfs2_ail_flush(gl, 0, revokes);
 	gfs2_trans_end(sdp);
+
 flush:
 	gfs2_log_flush(sdp, NULL, GFS2_LOG_HEAD_FLUSH_NORMAL |
 		       GFS2_LFC_AIL_EMPTY_GL);
diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
index 8e1ab8ed4abc..958810e533ad 100644
--- a/fs/gfs2/incore.h
+++ b/fs/gfs2/incore.h
@@ -490,7 +490,6 @@ struct gfs2_quota_data {
 enum {
 	TR_TOUCHED = 1,
 	TR_ATTACHED = 2,
-	TR_ALLOCED = 3,
 };
 
 struct gfs2_trans {
diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index e4dc23a24569..721d2d7f0efd 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -1114,7 +1114,6 @@ static void log_refund(struct gfs2_sbd *sdp, struct gfs2_trans *tr)
 	if (sdp->sd_log_tr) {
 		gfs2_merge_trans(sdp, tr);
 	} else if (tr->tr_num_buf_new || tr->tr_num_databuf_new) {
-		gfs2_assert_withdraw(sdp, test_bit(TR_ALLOCED, &tr->tr_flags));
 		sdp->sd_log_tr = tr;
 		set_bit(TR_ATTACHED, &tr->tr_flags);
 	}
diff --git a/fs/gfs2/trans.c b/fs/gfs2/trans.c
index 7705f04621f4..4f461ab37ced 100644
--- a/fs/gfs2/trans.c
+++ b/fs/gfs2/trans.c
@@ -37,8 +37,8 @@ static void gfs2_print_trans(struct gfs2_sbd *sdp, const struct gfs2_trans *tr)
 		tr->tr_num_revoke, tr->tr_num_revoke_rm);
 }
 
-int gfs2_trans_begin(struct gfs2_sbd *sdp, unsigned int blocks,
-		     unsigned int revokes)
+int __gfs2_trans_begin(struct gfs2_sbd *sdp, unsigned int blocks,
+		       unsigned int revokes, gfp_t gfp_mask)
 {
 	struct gfs2_trans *tr;
 	int error;
@@ -52,7 +52,7 @@ int gfs2_trans_begin(struct gfs2_sbd *sdp, unsigned int blocks,
 	if (!test_bit(SDF_JOURNAL_LIVE, &sdp->sd_flags))
 		return -EROFS;
 
-	tr = kmem_cache_zalloc(gfs2_trans_cachep, GFP_NOFS);
+	tr = kmem_cache_zalloc(gfs2_trans_cachep, gfp_mask);
 	if (!tr)
 		return -ENOMEM;
 
@@ -60,7 +60,6 @@ int gfs2_trans_begin(struct gfs2_sbd *sdp, unsigned int blocks,
 	tr->tr_blocks = blocks;
 	tr->tr_revokes = revokes;
 	tr->tr_reserved = 1;
-	set_bit(TR_ALLOCED, &tr->tr_flags);
 	if (blocks)
 		tr->tr_reserved += 6 + blocks;
 	if (revokes)
@@ -88,20 +87,23 @@ int gfs2_trans_begin(struct gfs2_sbd *sdp, unsigned int blocks,
 	return error;
 }
 
+int gfs2_trans_begin(struct gfs2_sbd *sdp, unsigned int blocks,
+		     unsigned int revokes)
+{
+	return __gfs2_trans_begin(sdp, blocks, revokes, GFP_NOFS);
+}
+
 void gfs2_trans_end(struct gfs2_sbd *sdp)
 {
 	struct gfs2_trans *tr = current->journal_info;
 	s64 nbuf;
-	int alloced = test_bit(TR_ALLOCED, &tr->tr_flags);
 
 	current->journal_info = NULL;
 
 	if (!test_bit(TR_TOUCHED, &tr->tr_flags)) {
 		gfs2_log_release(sdp, tr->tr_reserved);
-		if (alloced) {
-			gfs2_trans_free(sdp, tr);
-			sb_end_intwrite(sdp->sd_vfs);
-		}
+		gfs2_trans_free(sdp, tr);
+		sb_end_intwrite(sdp->sd_vfs);
 		return;
 	}
 
@@ -114,15 +116,14 @@ void gfs2_trans_end(struct gfs2_sbd *sdp)
 		gfs2_print_trans(sdp, tr);
 
 	gfs2_log_commit(sdp, tr);
-	if (alloced && !test_bit(TR_ATTACHED, &tr->tr_flags))
+	if (!test_bit(TR_ATTACHED, &tr->tr_flags))
 		gfs2_trans_free(sdp, tr);
 	up_read(&sdp->sd_log_flush_lock);
 
 	if (sdp->sd_vfs->s_flags & SB_SYNCHRONOUS)
 		gfs2_log_flush(sdp, NULL, GFS2_LOG_HEAD_FLUSH_NORMAL |
 			       GFS2_LFC_TRANS_END);
-	if (alloced)
-		sb_end_intwrite(sdp->sd_vfs);
+	sb_end_intwrite(sdp->sd_vfs);
 }
 
 static struct gfs2_bufdata *gfs2_alloc_bufdata(struct gfs2_glock *gl,
diff --git a/fs/gfs2/trans.h b/fs/gfs2/trans.h
index 83199ce5a5c5..9c732a5f28bf 100644
--- a/fs/gfs2/trans.h
+++ b/fs/gfs2/trans.h
@@ -34,6 +34,8 @@ static inline unsigned int gfs2_rg_blocks(const struct gfs2_inode *ip, unsigned
 	return rgd->rd_length;
 }
 
+extern int __gfs2_trans_begin(struct gfs2_sbd *sdp, unsigned int blocks,
+			      unsigned int revokes, gfp_t gfp_mask);
 extern int gfs2_trans_begin(struct gfs2_sbd *sdp, unsigned int blocks,
 			    unsigned int revokes);
 
-- 
2.26.2

[Cluster-devel] [PATCH v3 08/20] gfs2: Get rid of on-stack transactions

[Steven Whitehouse]

Hi,

On 27/01/2021 21:07, Andreas Gruenbacher wrote:
> On-stack transactions were introduced to work around a transaction glock
> deadlock in gfs2_trans_begin in commit d8348de06f70 ("GFS2: Fix deadlock
> on journal flush").  Subsequently, transaction glocks were eliminated in
> favor of the more efficient freeze glocks in commit 24972557b12c ("GFS2:
> remove transaction glock") without also removing the on-stack
> transactions.
>
> It has now turned out that committing on-stack transactions
> significantly complicates journal free space accounting when no system
> transaction (sdp->sd_log_tr) is active at the time.  It doesn't seem
> that on-stack transactions provide a significant benefit beyond their
> original purpose (as an optimization), so remove them to allow fixing
> the journal free space accounting in a reasonable way in a subsequent
> patch.
>
> FIXME: Can we better handle a gfs2_trans_begin failure in gfs2_ail_empty_gl?
> If we skip the __gfs2_ail_flush, we'll just end up with leftover items on
> gl_ail_list.

The reason for the on-stack allocation is to avoid the GFP_NOFAIL 
allocation here. Please don't add it back, we have gradually been 
working to eliminate those. Thoes allocations may not fail, but they 
might also take a long enough time that it would make little difference 
if they did. So perhaps we need to look at another solution?

Steve.


>
> Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
> ---
>   fs/gfs2/glops.c  | 29 +++++++----------------------
>   fs/gfs2/incore.h |  1 -
>   fs/gfs2/log.c    |  1 -
>   fs/gfs2/trans.c  | 25 +++++++++++++------------
>   fs/gfs2/trans.h  |  2 ++
>   5 files changed, 22 insertions(+), 36 deletions(-)
>
> diff --git a/fs/gfs2/glops.c b/fs/gfs2/glops.c
> index 3faa421568b0..853e590ccc15 100644
> --- a/fs/gfs2/glops.c
> +++ b/fs/gfs2/glops.c
> @@ -84,18 +84,11 @@ static void __gfs2_ail_flush(struct gfs2_glock *gl, bool fsync,
>   
>   static int gfs2_ail_empty_gl(struct gfs2_glock *gl)
>   {
> +	unsigned int revokes = atomic_read(&gl->gl_ail_count);
>   	struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
> -	struct gfs2_trans tr;
>   	int ret;
>   
> -	memset(&tr, 0, sizeof(tr));
> -	INIT_LIST_HEAD(&tr.tr_buf);
> -	INIT_LIST_HEAD(&tr.tr_databuf);
> -	INIT_LIST_HEAD(&tr.tr_ail1_list);
> -	INIT_LIST_HEAD(&tr.tr_ail2_list);
> -	tr.tr_revokes = atomic_read(&gl->gl_ail_count);
> -
> -	if (!tr.tr_revokes) {
> +	if (!revokes) {
>   		bool have_revokes;
>   		bool log_in_flight;
>   
> @@ -122,20 +115,12 @@ static int gfs2_ail_empty_gl(struct gfs2_glock *gl)
>   		return 0;
>   	}
>   
> -	/* A shortened, inline version of gfs2_trans_begin()
> -         * tr->alloced is not set since the transaction structure is
> -         * on the stack */
> -	tr.tr_reserved = 1 + gfs2_struct2blk(sdp, tr.tr_revokes);
> -	tr.tr_ip = _RET_IP_;
> -	ret = gfs2_log_reserve(sdp, tr.tr_reserved);
> -	if (ret < 0)
> -		return ret;
> -	WARN_ON_ONCE(current->journal_info);
> -	current->journal_info = &tr;
> -
> -	__gfs2_ail_flush(gl, 0, tr.tr_revokes);
> -
> +	ret = __gfs2_trans_begin(sdp, 0, revokes, GFP_NOFS | __GFP_NOFAIL);
> +	if (ret)
> +		goto flush;
> +	__gfs2_ail_flush(gl, 0, revokes);
>   	gfs2_trans_end(sdp);
> +
>   flush:
>   	gfs2_log_flush(sdp, NULL, GFS2_LOG_HEAD_FLUSH_NORMAL |
>   		       GFS2_LFC_AIL_EMPTY_GL);
> diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
> index 8e1ab8ed4abc..958810e533ad 100644
> --- a/fs/gfs2/incore.h
> +++ b/fs/gfs2/incore.h
> @@ -490,7 +490,6 @@ struct gfs2_quota_data {
>   enum {
>   	TR_TOUCHED = 1,
>   	TR_ATTACHED = 2,
> -	TR_ALLOCED = 3,
>   };
>   
>   struct gfs2_trans {
> diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
> index e4dc23a24569..721d2d7f0efd 100644
> --- a/fs/gfs2/log.c
> +++ b/fs/gfs2/log.c
> @@ -1114,7 +1114,6 @@ static void log_refund(struct gfs2_sbd *sdp, struct gfs2_trans *tr)
>   	if (sdp->sd_log_tr) {
>   		gfs2_merge_trans(sdp, tr);
>   	} else if (tr->tr_num_buf_new || tr->tr_num_databuf_new) {
> -		gfs2_assert_withdraw(sdp, test_bit(TR_ALLOCED, &tr->tr_flags));
>   		sdp->sd_log_tr = tr;
>   		set_bit(TR_ATTACHED, &tr->tr_flags);
>   	}
> diff --git a/fs/gfs2/trans.c b/fs/gfs2/trans.c
> index 7705f04621f4..4f461ab37ced 100644
> --- a/fs/gfs2/trans.c
> +++ b/fs/gfs2/trans.c
> @@ -37,8 +37,8 @@ static void gfs2_print_trans(struct gfs2_sbd *sdp, const struct gfs2_trans *tr)
>   		tr->tr_num_revoke, tr->tr_num_revoke_rm);
>   }
>   
> -int gfs2_trans_begin(struct gfs2_sbd *sdp, unsigned int blocks,
> -		     unsigned int revokes)
> +int __gfs2_trans_begin(struct gfs2_sbd *sdp, unsigned int blocks,
> +		       unsigned int revokes, gfp_t gfp_mask)
>   {
>   	struct gfs2_trans *tr;
>   	int error;
> @@ -52,7 +52,7 @@ int gfs2_trans_begin(struct gfs2_sbd *sdp, unsigned int blocks,
>   	if (!test_bit(SDF_JOURNAL_LIVE, &sdp->sd_flags))
>   		return -EROFS;
>   
> -	tr = kmem_cache_zalloc(gfs2_trans_cachep, GFP_NOFS);
> +	tr = kmem_cache_zalloc(gfs2_trans_cachep, gfp_mask);
>   	if (!tr)
>   		return -ENOMEM;
>   
> @@ -60,7 +60,6 @@ int gfs2_trans_begin(struct gfs2_sbd *sdp, unsigned int blocks,
>   	tr->tr_blocks = blocks;
>   	tr->tr_revokes = revokes;
>   	tr->tr_reserved = 1;
> -	set_bit(TR_ALLOCED, &tr->tr_flags);
>   	if (blocks)
>   		tr->tr_reserved += 6 + blocks;
>   	if (revokes)
> @@ -88,20 +87,23 @@ int gfs2_trans_begin(struct gfs2_sbd *sdp, unsigned int blocks,
>   	return error;
>   }
>   
> +int gfs2_trans_begin(struct gfs2_sbd *sdp, unsigned int blocks,
> +		     unsigned int revokes)
> +{
> +	return __gfs2_trans_begin(sdp, blocks, revokes, GFP_NOFS);
> +}
> +
>   void gfs2_trans_end(struct gfs2_sbd *sdp)
>   {
>   	struct gfs2_trans *tr = current->journal_info;
>   	s64 nbuf;
> -	int alloced = test_bit(TR_ALLOCED, &tr->tr_flags);
>   
>   	current->journal_info = NULL;
>   
>   	if (!test_bit(TR_TOUCHED, &tr->tr_flags)) {
>   		gfs2_log_release(sdp, tr->tr_reserved);
> -		if (alloced) {
> -			gfs2_trans_free(sdp, tr);
> -			sb_end_intwrite(sdp->sd_vfs);
> -		}
> +		gfs2_trans_free(sdp, tr);
> +		sb_end_intwrite(sdp->sd_vfs);
>   		return;
>   	}
>   
> @@ -114,15 +116,14 @@ void gfs2_trans_end(struct gfs2_sbd *sdp)
>   		gfs2_print_trans(sdp, tr);
>   
>   	gfs2_log_commit(sdp, tr);
> -	if (alloced && !test_bit(TR_ATTACHED, &tr->tr_flags))
> +	if (!test_bit(TR_ATTACHED, &tr->tr_flags))
>   		gfs2_trans_free(sdp, tr);
>   	up_read(&sdp->sd_log_flush_lock);
>   
>   	if (sdp->sd_vfs->s_flags & SB_SYNCHRONOUS)
>   		gfs2_log_flush(sdp, NULL, GFS2_LOG_HEAD_FLUSH_NORMAL |
>   			       GFS2_LFC_TRANS_END);
> -	if (alloced)
> -		sb_end_intwrite(sdp->sd_vfs);
> +	sb_end_intwrite(sdp->sd_vfs);
>   }
>   
>   static struct gfs2_bufdata *gfs2_alloc_bufdata(struct gfs2_glock *gl,
> diff --git a/fs/gfs2/trans.h b/fs/gfs2/trans.h
> index 83199ce5a5c5..9c732a5f28bf 100644
> --- a/fs/gfs2/trans.h
> +++ b/fs/gfs2/trans.h
> @@ -34,6 +34,8 @@ static inline unsigned int gfs2_rg_blocks(const struct gfs2_inode *ip, unsigned
>   	return rgd->rd_length;
>   }
>   
> +extern int __gfs2_trans_begin(struct gfs2_sbd *sdp, unsigned int blocks,
> +			      unsigned int revokes, gfp_t gfp_mask);
>   extern int gfs2_trans_begin(struct gfs2_sbd *sdp, unsigned int blocks,
>   			    unsigned int revokes);
>   

[Cluster-devel] [PATCH v3 09/20] gfs2: Get rid of sd_reserving_log

[Andreas Gruenbacher]

This counter and the associated wait queue are only used so that
gfs2_make_fs_ro can efficiently wait for all pending log space
allocations to fail after setting the filesystem to read-only.  This
comes at the cost of waking up that wait queue very frequently.

Instead, when gfs2_log_reserve fails because the filesystem has become
read-only, Wake up sd_log_waitq.  In gfs2_make_fs_ro, set the file
system read-only and then wait until all the log space has been
released.  Give up and report the problem after a while.  With that,
sd_reserving_log and sd_reserving_log_wait can be removed.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
 fs/gfs2/incore.h     |  3 ---
 fs/gfs2/log.c        | 17 ++++++++++-------
 fs/gfs2/log.h        |  1 +
 fs/gfs2/ops_fstype.c |  2 --
 fs/gfs2/super.c      | 12 ++++++------
 fs/gfs2/trans.c      |  5 ++++-
 6 files changed, 21 insertions(+), 19 deletions(-)

diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
index 958810e533ad..c155fd39bc98 100644
--- a/fs/gfs2/incore.h
+++ b/fs/gfs2/incore.h
@@ -848,9 +848,6 @@ struct gfs2_sbd {
 	int sd_log_error; /* First log error */
 	wait_queue_head_t sd_withdraw_wait;
 
-	atomic_t sd_reserving_log;
-	wait_queue_head_t sd_reserving_log_wait;
-
 	unsigned int sd_log_flush_head;
 
 	spinlock_t sd_ail_lock;
diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index 721d2d7f0efd..2e84ba153cdf 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -397,6 +397,15 @@ static void ail2_empty(struct gfs2_sbd *sdp, unsigned int new_tail)
 	spin_unlock(&sdp->sd_ail_lock);
 }
 
+/**
+ * gfs2_log_is_empty - Check if the log is empty
+ * @sdp: The GFS2 superblock
+ */
+
+bool gfs2_log_is_empty(struct gfs2_sbd *sdp) {
+	return atomic_read(&sdp->sd_log_blks_free) == sdp->sd_jdesc->jd_blocks;
+}
+
 /**
  * gfs2_log_release - Release a given number of log blocks
  * @sdp: The GFS2 superblock
@@ -461,13 +470,9 @@ int gfs2_log_reserve(struct gfs2_sbd *sdp, unsigned int blks)
 		} while(free_blocks <= wanted);
 		finish_wait(&sdp->sd_log_waitq, &wait);
 	}
-	atomic_inc(&sdp->sd_reserving_log);
 	if (atomic_cmpxchg(&sdp->sd_log_blks_free, free_blocks,
-				free_blocks - blks) != free_blocks) {
-		if (atomic_dec_and_test(&sdp->sd_reserving_log))
-			wake_up(&sdp->sd_reserving_log_wait);
+				free_blocks - blks) != free_blocks)
 		goto retry;
-	}
 	atomic_sub(blks, &sdp->sd_log_blks_needed);
 	trace_gfs2_log_blocks(sdp, -blks);
 
@@ -483,8 +488,6 @@ int gfs2_log_reserve(struct gfs2_sbd *sdp, unsigned int blks)
 		gfs2_log_release(sdp, blks);
 		ret = -EROFS;
 	}
-	if (atomic_dec_and_test(&sdp->sd_reserving_log))
-		wake_up(&sdp->sd_reserving_log_wait);
 	return ret;
 }
 
diff --git a/fs/gfs2/log.h b/fs/gfs2/log.h
index a9cdbc990edf..16efbe614279 100644
--- a/fs/gfs2/log.h
+++ b/fs/gfs2/log.h
@@ -64,6 +64,7 @@ static inline void gfs2_ordered_add_inode(struct gfs2_inode *ip)
 extern void gfs2_ordered_del_inode(struct gfs2_inode *ip);
 extern unsigned int gfs2_struct2blk(struct gfs2_sbd *sdp, unsigned int nstruct);
 extern void gfs2_remove_from_ail(struct gfs2_bufdata *bd);
+extern bool gfs2_log_is_empty(struct gfs2_sbd *sdp);
 extern void gfs2_log_release(struct gfs2_sbd *sdp, unsigned int blks);
 extern int gfs2_log_reserve(struct gfs2_sbd *sdp, unsigned int blks);
 extern void gfs2_write_log_header(struct gfs2_sbd *sdp, struct gfs2_jdesc *jd,
diff --git a/fs/gfs2/ops_fstype.c b/fs/gfs2/ops_fstype.c
index 61fce59cb4d3..986dc2ebebf0 100644
--- a/fs/gfs2/ops_fstype.c
+++ b/fs/gfs2/ops_fstype.c
@@ -136,8 +136,6 @@ static struct gfs2_sbd *init_sbd(struct super_block *sb)
 
 	init_rwsem(&sdp->sd_log_flush_lock);
 	atomic_set(&sdp->sd_log_in_flight, 0);
-	atomic_set(&sdp->sd_reserving_log, 0);
-	init_waitqueue_head(&sdp->sd_reserving_log_wait);
 	init_waitqueue_head(&sdp->sd_log_flush_wait);
 	atomic_set(&sdp->sd_freeze_state, SFS_UNFROZEN);
 	mutex_init(&sdp->sd_freeze_mutex);
diff --git a/fs/gfs2/super.c b/fs/gfs2/super.c
index ed7a829e9ffe..f188277f7d48 100644
--- a/fs/gfs2/super.c
+++ b/fs/gfs2/super.c
@@ -645,13 +645,13 @@ int gfs2_make_fs_ro(struct gfs2_sbd *sdp)
 
 		gfs2_log_flush(sdp, NULL, GFS2_LOG_HEAD_FLUSH_SHUTDOWN |
 			       GFS2_LFC_MAKE_FS_RO);
-		wait_event(sdp->sd_reserving_log_wait,
-			   atomic_read(&sdp->sd_reserving_log) == 0);
-		gfs2_assert_warn(sdp, atomic_read(&sdp->sd_log_blks_free) ==
-				 sdp->sd_jdesc->jd_blocks);
+		wait_event_timeout(sdp->sd_log_waitq,
+				   gfs2_log_is_empty(sdp),
+				   HZ * 5);
+		gfs2_assert_warn(sdp, gfs2_log_is_empty(sdp));
 	} else {
-		wait_event_timeout(sdp->sd_reserving_log_wait,
-				   atomic_read(&sdp->sd_reserving_log) == 0,
+		wait_event_timeout(sdp->sd_log_waitq,
+				   gfs2_log_is_empty(sdp),
 				   HZ * 5);
 	}
 	if (gfs2_holder_initialized(&freeze_gh))
diff --git a/fs/gfs2/trans.c b/fs/gfs2/trans.c
index 4f461ab37ced..e33cb8da056a 100644
--- a/fs/gfs2/trans.c
+++ b/fs/gfs2/trans.c
@@ -73,8 +73,11 @@ int __gfs2_trans_begin(struct gfs2_sbd *sdp, unsigned int blocks,
 	sb_start_intwrite(sdp->sd_vfs);
 
 	error = gfs2_log_reserve(sdp, tr->tr_reserved);
-	if (error)
+	if (error) {
+		if (error == -EROFS)
+			wake_up(&sdp->sd_log_waitq);
 		goto fail;
+	}
 
 	current->journal_info = tr;
 
-- 
2.26.2

[Cluster-devel] [PATCH v3 10/20] gfs2: Move lock flush locking to gfs2_trans_{begin, end}

[Andreas Gruenbacher]

Move the read locking of sd_log_flush_lock from gfs2_log_reserve to
gfs2_trans_begin, and its unlocking from gfs2_log_release to
gfs2_trans_end.  Use gfs2_log_release in two places in which it was open
coded before.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
 fs/gfs2/log.c   | 28 +++-------------------------
 fs/gfs2/log.h   |  2 +-
 fs/gfs2/trans.c | 23 ++++++++++++++++-------
 3 files changed, 20 insertions(+), 33 deletions(-)

diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index 2e84ba153cdf..2e74137322bd 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -420,7 +420,6 @@ void gfs2_log_release(struct gfs2_sbd *sdp, unsigned int blks)
 	trace_gfs2_log_blocks(sdp, blks);
 	gfs2_assert_withdraw(sdp, atomic_read(&sdp->sd_log_blks_free) <=
 				  sdp->sd_jdesc->jd_blocks);
-	up_read(&sdp->sd_log_flush_lock);
 }
 
 /**
@@ -439,22 +438,16 @@ void gfs2_log_release(struct gfs2_sbd *sdp, unsigned int blks)
  * with queued waiters, we use an exclusive wait. This means that when we
  * get woken with enough journal space to get our reservation, we need to
  * wake the next waiter on the list.
- *
- * Returns: errno
  */
 
-int gfs2_log_reserve(struct gfs2_sbd *sdp, unsigned int blks)
+void gfs2_log_reserve(struct gfs2_sbd *sdp, unsigned int blks)
 {
-	int ret = 0;
 	unsigned reserved_blks = 7 * (4096 / sdp->sd_vfs->s_blocksize);
 	unsigned wanted = blks + reserved_blks;
 	DEFINE_WAIT(wait);
 	int did_wait = 0;
 	unsigned int free_blocks;
 
-	if (gfs2_assert_warn(sdp, blks) ||
-	    gfs2_assert_warn(sdp, blks <= sdp->sd_jdesc->jd_blocks))
-		return -EINVAL;
 	atomic_add(blks, &sdp->sd_log_blks_needed);
 retry:
 	free_blocks = atomic_read(&sdp->sd_log_blks_free);
@@ -482,13 +475,6 @@ int gfs2_log_reserve(struct gfs2_sbd *sdp, unsigned int blks)
 	 */
 	if (unlikely(did_wait))
 		wake_up(&sdp->sd_log_waitq);
-
-	down_read(&sdp->sd_log_flush_lock);
-	if (unlikely(!test_bit(SDF_JOURNAL_LIVE, &sdp->sd_flags))) {
-		gfs2_log_release(sdp, blks);
-		ret = -EROFS;
-	}
-	return ret;
 }
 
 /**
@@ -585,12 +571,7 @@ static void log_pull_tail(struct gfs2_sbd *sdp, unsigned int new_tail)
 	unsigned int dist = log_distance(sdp, new_tail, sdp->sd_log_tail);
 
 	ail2_empty(sdp, new_tail);
-
-	atomic_add(dist, &sdp->sd_log_blks_free);
-	trace_gfs2_log_blocks(sdp, dist);
-	gfs2_assert_withdraw(sdp, atomic_read(&sdp->sd_log_blks_free) <=
-			     sdp->sd_jdesc->jd_blocks);
-
+	gfs2_log_release(sdp, dist);
 	sdp->sd_log_tail = new_tail;
 }
 
@@ -1126,10 +1107,7 @@ static void log_refund(struct gfs2_sbd *sdp, struct gfs2_trans *tr)
 	maxres = sdp->sd_log_blks_reserved + tr->tr_reserved;
 	gfs2_assert_withdraw(sdp, maxres >= reserved);
 	unused = maxres - reserved;
-	atomic_add(unused, &sdp->sd_log_blks_free);
-	trace_gfs2_log_blocks(sdp, unused);
-	gfs2_assert_withdraw(sdp, atomic_read(&sdp->sd_log_blks_free) <=
-			     sdp->sd_jdesc->jd_blocks);
+	gfs2_log_release(sdp, unused);
 	sdp->sd_log_blks_reserved = reserved;
 
 	gfs2_log_unlock(sdp);
diff --git a/fs/gfs2/log.h b/fs/gfs2/log.h
index 16efbe614279..cbc097ca9244 100644
--- a/fs/gfs2/log.h
+++ b/fs/gfs2/log.h
@@ -66,7 +66,7 @@ extern unsigned int gfs2_struct2blk(struct gfs2_sbd *sdp, unsigned int nstruct);
 extern void gfs2_remove_from_ail(struct gfs2_bufdata *bd);
 extern bool gfs2_log_is_empty(struct gfs2_sbd *sdp);
 extern void gfs2_log_release(struct gfs2_sbd *sdp, unsigned int blks);
-extern int gfs2_log_reserve(struct gfs2_sbd *sdp, unsigned int blks);
+extern void gfs2_log_reserve(struct gfs2_sbd *sdp, unsigned int blks);
 extern void gfs2_write_log_header(struct gfs2_sbd *sdp, struct gfs2_jdesc *jd,
 				  u64 seq, u32 tail, u32 lblock, u32 flags,
 				  int op_flags);
diff --git a/fs/gfs2/trans.c b/fs/gfs2/trans.c
index e33cb8da056a..c9d8247ffa19 100644
--- a/fs/gfs2/trans.c
+++ b/fs/gfs2/trans.c
@@ -70,12 +70,22 @@ int __gfs2_trans_begin(struct gfs2_sbd *sdp, unsigned int blocks,
 	INIT_LIST_HEAD(&tr->tr_ail1_list);
 	INIT_LIST_HEAD(&tr->tr_ail2_list);
 
+	if (gfs2_assert_warn(sdp, tr->tr_reserved <= sdp->sd_jdesc->jd_blocks)) {
+		error = -EINVAL;
+		goto fail;
+	}
+
 	sb_start_intwrite(sdp->sd_vfs);
 
-	error = gfs2_log_reserve(sdp, tr->tr_reserved);
-	if (error) {
-		if (error == -EROFS)
-			wake_up(&sdp->sd_log_waitq);
+	gfs2_log_reserve(sdp, tr->tr_reserved);
+
+	down_read(&sdp->sd_log_flush_lock);
+	if (unlikely(!test_bit(SDF_JOURNAL_LIVE, &sdp->sd_flags))) {
+		gfs2_log_release(sdp, tr->tr_reserved);
+		up_read(&sdp->sd_log_flush_lock);
+		sb_end_intwrite(sdp->sd_vfs);
+		wake_up(&sdp->sd_log_waitq);
+		error = -EROFS;
 		goto fail;
 	}
 
@@ -84,9 +94,7 @@ int __gfs2_trans_begin(struct gfs2_sbd *sdp, unsigned int blocks,
 	return 0;
 
 fail:
-	sb_end_intwrite(sdp->sd_vfs);
 	kmem_cache_free(gfs2_trans_cachep, tr);
-
 	return error;
 }
 
@@ -105,8 +113,9 @@ void gfs2_trans_end(struct gfs2_sbd *sdp)
 
 	if (!test_bit(TR_TOUCHED, &tr->tr_flags)) {
 		gfs2_log_release(sdp, tr->tr_reserved);
-		gfs2_trans_free(sdp, tr);
+		up_read(&sdp->sd_log_flush_lock);
 		sb_end_intwrite(sdp->sd_vfs);
+		gfs2_trans_free(sdp, tr);
 		return;
 	}
 
-- 
2.26.2

[Cluster-devel] [PATCH v3 11/20] gfs2: Don't wait for journal flush in clean_journal

[Andreas Gruenbacher]

Commit 588bff95c94e added gfs2_write_log_header() and started using it in
clean_journal(), with an additional call to log_flush_wait() at the end of
gfs2_write_log_header() which is unnecessary for clean_journal().  Move
that call out of gfs2_write_log_header() to restore the previous behavior.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
 fs/gfs2/log.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index 2e74137322bd..4a2b121b34d0 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -757,7 +757,7 @@ void gfs2_write_log_header(struct gfs2_sbd *sdp, struct gfs2_jdesc *jd,
 	u64 dblock;
 
 	if (gfs2_withdrawn(sdp))
-		goto out;
+		return;
 
 	page = mempool_alloc(gfs2_page_pool, GFP_NOIO);
 	lh = page_address(page);
@@ -812,8 +812,6 @@ void gfs2_write_log_header(struct gfs2_sbd *sdp, struct gfs2_jdesc *jd,
 
 	gfs2_log_write(sdp, page, sb->s_blocksize, 0, dblock);
 	gfs2_log_submit_bio(&sdp->sd_log_bio, REQ_OP_WRITE | op_flags);
-out:
-	log_flush_wait(sdp);
 }
 
 /**
@@ -842,6 +840,7 @@ static void log_write_header(struct gfs2_sbd *sdp, u32 flags)
 	gfs2_write_log_header(sdp, sdp->sd_jdesc, sdp->sd_log_sequence++, tail,
 			      sdp->sd_log_flush_head, flags, op_flags);
 	gfs2_log_incr_head(sdp);
+	log_flush_wait(sdp);
 
 	if (sdp->sd_log_tail != tail)
 		log_pull_tail(sdp, tail);
-- 
2.26.2

[Cluster-devel] [PATCH v3 12/20] gfs2: Clean up gfs2_log_reserve

[Andreas Gruenbacher]

Wake up log waiters in gfs2_log_release when log space has actually become
available.  This is a much better place for the wakeup than gfs2_logd.

Check if enough log space is immeditely available before anything else.  If
there isn't, use io_wait_event to wait instead of open-coding it.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
 fs/gfs2/log.c   | 58 +++++++++++++++++++++----------------------------
 fs/gfs2/trans.c |  3 +--
 2 files changed, 26 insertions(+), 35 deletions(-)

diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index 4a2b121b34d0..24a292065b9c 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -415,11 +415,12 @@ bool gfs2_log_is_empty(struct gfs2_sbd *sdp) {
 
 void gfs2_log_release(struct gfs2_sbd *sdp, unsigned int blks)
 {
-
 	atomic_add(blks, &sdp->sd_log_blks_free);
 	trace_gfs2_log_blocks(sdp, blks);
 	gfs2_assert_withdraw(sdp, atomic_read(&sdp->sd_log_blks_free) <=
 				  sdp->sd_jdesc->jd_blocks);
+	if (atomic_read(&sdp->sd_log_blks_needed))
+		wake_up(&sdp->sd_log_waitq);
 }
 
 /**
@@ -444,36 +445,33 @@ void gfs2_log_reserve(struct gfs2_sbd *sdp, unsigned int blks)
 {
 	unsigned reserved_blks = 7 * (4096 / sdp->sd_vfs->s_blocksize);
 	unsigned wanted = blks + reserved_blks;
-	DEFINE_WAIT(wait);
-	int did_wait = 0;
 	unsigned int free_blocks;
 
-	atomic_add(blks, &sdp->sd_log_blks_needed);
-retry:
 	free_blocks = atomic_read(&sdp->sd_log_blks_free);
-	if (unlikely(free_blocks <= wanted)) {
-		do {
-			prepare_to_wait_exclusive(&sdp->sd_log_waitq, &wait,
-					TASK_UNINTERRUPTIBLE);
+	while (free_blocks >= wanted) {
+		if (atomic_try_cmpxchg(&sdp->sd_log_blks_free, &free_blocks,
+				       free_blocks - blks))
+			return;
+	}
+
+	atomic_add(blks, &sdp->sd_log_blks_needed);
+	for (;;) {
+		if (current != sdp->sd_logd_process)
 			wake_up(&sdp->sd_logd_waitq);
-			did_wait = 1;
-			if (atomic_read(&sdp->sd_log_blks_free) <= wanted)
-				io_schedule();
-			free_blocks = atomic_read(&sdp->sd_log_blks_free);
-		} while(free_blocks <= wanted);
-		finish_wait(&sdp->sd_log_waitq, &wait);
+		io_wait_event(sdp->sd_log_waitq,
+			(free_blocks = atomic_read(&sdp->sd_log_blks_free),
+			 free_blocks >= wanted));
+		do {
+			if (atomic_try_cmpxchg(&sdp->sd_log_blks_free,
+					       &free_blocks,
+					       free_blocks - blks))
+				goto reserved;
+		} while (free_blocks >= wanted);
 	}
-	if (atomic_cmpxchg(&sdp->sd_log_blks_free, free_blocks,
-				free_blocks - blks) != free_blocks)
-		goto retry;
-	atomic_sub(blks, &sdp->sd_log_blks_needed);
-	trace_gfs2_log_blocks(sdp, -blks);
 
-	/*
-	 * If we waited, then so might others, wake them up _after_ we get
-	 * our share of the log.
-	 */
-	if (unlikely(did_wait))
+reserved:
+	trace_gfs2_log_blocks(sdp, -blks);
+	if (atomic_sub_return(blks, &sdp->sd_log_blks_needed))
 		wake_up(&sdp->sd_log_waitq);
 }
 
@@ -1106,7 +1104,8 @@ static void log_refund(struct gfs2_sbd *sdp, struct gfs2_trans *tr)
 	maxres = sdp->sd_log_blks_reserved + tr->tr_reserved;
 	gfs2_assert_withdraw(sdp, maxres >= reserved);
 	unused = maxres - reserved;
-	gfs2_log_release(sdp, unused);
+	if (unused)
+		gfs2_log_release(sdp, unused);
 	sdp->sd_log_blks_reserved = reserved;
 
 	gfs2_log_unlock(sdp);
@@ -1191,7 +1190,6 @@ int gfs2_logd(void *data)
 	struct gfs2_sbd *sdp = data;
 	unsigned long t = 1;
 	DEFINE_WAIT(wait);
-	bool did_flush;
 
 	while (!kthread_should_stop()) {
 
@@ -1210,12 +1208,10 @@ int gfs2_logd(void *data)
 			continue;
 		}
 
-		did_flush = false;
 		if (gfs2_jrnl_flush_reqd(sdp) || t == 0) {
 			gfs2_ail1_empty(sdp, 0);
 			gfs2_log_flush(sdp, NULL, GFS2_LOG_HEAD_FLUSH_NORMAL |
 				       GFS2_LFC_LOGD_JFLUSH_REQD);
-			did_flush = true;
 		}
 
 		if (gfs2_ail_flush_reqd(sdp)) {
@@ -1224,12 +1220,8 @@ int gfs2_logd(void *data)
 			gfs2_ail1_empty(sdp, 0);
 			gfs2_log_flush(sdp, NULL, GFS2_LOG_HEAD_FLUSH_NORMAL |
 				       GFS2_LFC_LOGD_AIL_FLUSH_REQD);
-			did_flush = true;
 		}
 
-		if (!gfs2_ail_flush_reqd(sdp) || did_flush)
-			wake_up(&sdp->sd_log_waitq);
-
 		t = gfs2_tune_get(sdp, gt_logd_secs) * HZ;
 
 		try_to_freeze();
diff --git a/fs/gfs2/trans.c b/fs/gfs2/trans.c
index c9d8247ffa19..058492cf44fa 100644
--- a/fs/gfs2/trans.c
+++ b/fs/gfs2/trans.c
@@ -81,10 +81,9 @@ int __gfs2_trans_begin(struct gfs2_sbd *sdp, unsigned int blocks,
 
 	down_read(&sdp->sd_log_flush_lock);
 	if (unlikely(!test_bit(SDF_JOURNAL_LIVE, &sdp->sd_flags))) {
-		gfs2_log_release(sdp, tr->tr_reserved);
 		up_read(&sdp->sd_log_flush_lock);
+		gfs2_log_release(sdp, tr->tr_reserved);
 		sb_end_intwrite(sdp->sd_vfs);
-		wake_up(&sdp->sd_log_waitq);
 		error = -EROFS;
 		goto fail;
 	}
-- 
2.26.2

[Cluster-devel] [PATCH v3 13/20] gfs2: Use a tighter bound in gfs2_trans_begin

[Andreas Gruenbacher]

Use a tighter bound for the number of blocks required by transactions in
gfs2_trans_begin: in the worst case, we'll have mixed data and metadata,
so we'll need a log desciptor for each type.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
 fs/gfs2/trans.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/fs/gfs2/trans.c b/fs/gfs2/trans.c
index 058492cf44fa..3675e92f2857 100644
--- a/fs/gfs2/trans.c
+++ b/fs/gfs2/trans.c
@@ -60,8 +60,14 @@ int __gfs2_trans_begin(struct gfs2_sbd *sdp, unsigned int blocks,
 	tr->tr_blocks = blocks;
 	tr->tr_revokes = revokes;
 	tr->tr_reserved = 1;
-	if (blocks)
-		tr->tr_reserved += 6 + blocks;
+	if (blocks) {
+		/*
+		 * The reserved blocks are either used for data or metadata.
+		 * We can have mixed data and metadata, each with its own log
+		 * descriptor block; see calc_reserved().
+		 */
+		tr->tr_reserved += blocks + 1 + DIV_ROUND_UP(blocks - 1, databuf_limit(sdp));
+	}
 	if (revokes)
 		tr->tr_reserved += gfs2_struct2blk(sdp, revokes);
 	INIT_LIST_HEAD(&tr->tr_databuf);
-- 
2.26.2

[Cluster-devel] [PATCH v3 14/20] gfs2: Get rid of current_tail()

[Andreas Gruenbacher]

Keep the current value of the updated log tail in the super block as
sb_log_flush_tail instead of computing it on the fly.  This avoids
unnecessary sd_ail_lock taking and cleans up the code.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
 fs/gfs2/incore.h |  5 ++--
 fs/gfs2/log.c    | 72 +++++++++++++++++++++++++-----------------------
 fs/gfs2/log.h    |  4 ++-
 3 files changed, 44 insertions(+), 37 deletions(-)

diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
index c155fd39bc98..fdf4d942bb1d 100644
--- a/fs/gfs2/incore.h
+++ b/fs/gfs2/incore.h
@@ -837,8 +837,6 @@ struct gfs2_sbd {
 	wait_queue_head_t sd_logd_waitq;
 
 	u64 sd_log_sequence;
-	unsigned int sd_log_head;
-	unsigned int sd_log_tail;
 	int sd_log_idle;
 
 	struct rw_semaphore sd_log_flush_lock;
@@ -848,6 +846,9 @@ struct gfs2_sbd {
 	int sd_log_error; /* First log error */
 	wait_queue_head_t sd_withdraw_wait;
 
+	unsigned int sd_log_tail;
+	unsigned int sd_log_flush_tail;
+	unsigned int sd_log_head;
 	unsigned int sd_log_flush_head;
 
 	spinlock_t sd_ail_lock;
diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index 24a292065b9c..1ca5f2c468d5 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -242,6 +242,28 @@ static void gfs2_ail1_start(struct gfs2_sbd *sdp)
 	return gfs2_ail1_flush(sdp, &wbc);
 }
 
+static void gfs2_log_update_flush_tail(struct gfs2_sbd *sdp)
+{
+	unsigned int new_flush_tail = sdp->sd_log_head;
+	struct gfs2_trans *tr;
+
+	if (!list_empty(&sdp->sd_ail1_list)) {
+		tr = list_last_entry(&sdp->sd_ail1_list,
+				     struct gfs2_trans, tr_list);
+		new_flush_tail = tr->tr_first;
+	}
+	sdp->sd_log_flush_tail = new_flush_tail;
+}
+
+static void gfs2_log_update_head(struct gfs2_sbd *sdp)
+{
+	unsigned int new_head = sdp->sd_log_flush_head;
+
+	if (sdp->sd_log_flush_tail == sdp->sd_log_head)
+		sdp->sd_log_flush_tail = new_head;
+	sdp->sd_log_head = new_head;
+}
+
 /**
  * gfs2_ail1_empty_one - Check whether or not a trans in the AIL has been synced
  * @sdp: the filesystem
@@ -317,6 +339,7 @@ static int gfs2_ail1_empty(struct gfs2_sbd *sdp, int max_revokes)
 		else
 			oldest_tr = 0;
 	}
+	gfs2_log_update_flush_tail(sdp);
 	ret = list_empty(&sdp->sd_ail1_list);
 	spin_unlock(&sdp->sd_ail_lock);
 
@@ -544,30 +567,14 @@ static unsigned int calc_reserved(struct gfs2_sbd *sdp)
 	return reserved;
 }
 
-static unsigned int current_tail(struct gfs2_sbd *sdp)
-{
-	struct gfs2_trans *tr;
-	unsigned int tail;
-
-	spin_lock(&sdp->sd_ail_lock);
-
-	if (list_empty(&sdp->sd_ail1_list)) {
-		tail = sdp->sd_log_head;
-	} else {
-		tr = list_last_entry(&sdp->sd_ail1_list, struct gfs2_trans,
-				tr_list);
-		tail = tr->tr_first;
-	}
-
-	spin_unlock(&sdp->sd_ail_lock);
-
-	return tail;
-}
-
-static void log_pull_tail(struct gfs2_sbd *sdp, unsigned int new_tail)
+static void log_pull_tail(struct gfs2_sbd *sdp)
 {
-	unsigned int dist = log_distance(sdp, new_tail, sdp->sd_log_tail);
+	unsigned int new_tail = sdp->sd_log_flush_tail;
+	unsigned int dist;
 
+	if (new_tail == sdp->sd_log_tail)
+		return;
+	dist = log_distance(sdp, new_tail, sdp->sd_log_tail);
 	ail2_empty(sdp, new_tail);
 	gfs2_log_release(sdp, dist);
 	sdp->sd_log_tail = new_tail;
@@ -822,26 +829,23 @@ void gfs2_write_log_header(struct gfs2_sbd *sdp, struct gfs2_jdesc *jd,
 
 static void log_write_header(struct gfs2_sbd *sdp, u32 flags)
 {
-	unsigned int tail;
 	int op_flags = REQ_PREFLUSH | REQ_FUA | REQ_META | REQ_SYNC;
 	enum gfs2_freeze_state state = atomic_read(&sdp->sd_freeze_state);
 
 	gfs2_assert_withdraw(sdp, (state != SFS_FROZEN));
-	tail = current_tail(sdp);
 
 	if (test_bit(SDF_NOBARRIERS, &sdp->sd_flags)) {
 		gfs2_ordered_wait(sdp);
 		log_flush_wait(sdp);
 		op_flags = REQ_SYNC | REQ_META | REQ_PRIO;
 	}
-	sdp->sd_log_idle = (tail == sdp->sd_log_flush_head);
-	gfs2_write_log_header(sdp, sdp->sd_jdesc, sdp->sd_log_sequence++, tail,
-			      sdp->sd_log_flush_head, flags, op_flags);
+	sdp->sd_log_idle = (sdp->sd_log_flush_tail == sdp->sd_log_flush_head);
+	gfs2_write_log_header(sdp, sdp->sd_jdesc, sdp->sd_log_sequence++,
+			      sdp->sd_log_flush_tail, sdp->sd_log_flush_head,
+			      flags, op_flags);
 	gfs2_log_incr_head(sdp);
 	log_flush_wait(sdp);
-
-	if (sdp->sd_log_tail != tail)
-		log_pull_tail(sdp, tail);
+	log_pull_tail(sdp);
 }
 
 /**
@@ -991,7 +995,7 @@ void gfs2_log_flush(struct gfs2_sbd *sdp, struct gfs2_glock *gl, u32 flags)
 	if (sdp->sd_log_head != sdp->sd_log_flush_head) {
 		log_flush_wait(sdp);
 		log_write_header(sdp, flags);
-	} else if (sdp->sd_log_tail != current_tail(sdp) && !sdp->sd_log_idle) {
+	} else if (sdp->sd_log_tail != sdp->sd_log_flush_tail && !sdp->sd_log_idle) {
 		atomic_dec(&sdp->sd_log_blks_free); /* Adjust for unreserved buffer */
 		trace_gfs2_log_blocks(sdp, -1);
 		log_write_header(sdp, flags);
@@ -1001,7 +1005,7 @@ void gfs2_log_flush(struct gfs2_sbd *sdp, struct gfs2_glock *gl, u32 flags)
 	lops_after_commit(sdp, tr);
 
 	gfs2_log_lock(sdp);
-	sdp->sd_log_head = sdp->sd_log_flush_head;
+	gfs2_log_update_head(sdp);
 	sdp->sd_log_blks_reserved = 0;
 	sdp->sd_log_committed_revoke = 0;
 
@@ -1021,7 +1025,7 @@ void gfs2_log_flush(struct gfs2_sbd *sdp, struct gfs2_glock *gl, u32 flags)
 			atomic_dec(&sdp->sd_log_blks_free); /* Adjust for unreserved buffer */
 			trace_gfs2_log_blocks(sdp, -1);
 			log_write_header(sdp, flags);
-			sdp->sd_log_head = sdp->sd_log_flush_head;
+			gfs2_log_update_head(sdp);
 		}
 		if (flags & (GFS2_LOG_HEAD_FLUSH_SHUTDOWN |
 			     GFS2_LOG_HEAD_FLUSH_FREEZE))
@@ -1155,7 +1159,7 @@ static void gfs2_log_shutdown(struct gfs2_sbd *sdp)
 	gfs2_assert_warn(sdp, sdp->sd_log_head == sdp->sd_log_tail);
 	gfs2_assert_warn(sdp, list_empty(&sdp->sd_ail2_list));
 
-	sdp->sd_log_head = sdp->sd_log_flush_head;
+	gfs2_log_update_head(sdp);
 	sdp->sd_log_tail = sdp->sd_log_head;
 }
 
diff --git a/fs/gfs2/log.h b/fs/gfs2/log.h
index cbc097ca9244..b36a3539f352 100644
--- a/fs/gfs2/log.h
+++ b/fs/gfs2/log.h
@@ -43,7 +43,9 @@ static inline void gfs2_log_pointers_init(struct gfs2_sbd *sdp,
 	if (++value == sdp->sd_jdesc->jd_blocks) {
 		value = 0;
 	}
-	sdp->sd_log_head = sdp->sd_log_tail = value;
+	sdp->sd_log_tail = value;
+	sdp->sd_log_flush_tail = value;
+	sdp->sd_log_head = value;
 }
 
 static inline void gfs2_ordered_add_inode(struct gfs2_inode *ip)
-- 
2.26.2

[Cluster-devel] [PATCH v3 15/20] gfs2: Move function gfs2_ail_empty_tr

[Andreas Gruenbacher]

Move this function further up in log.c so that we can use it in the next patch.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
 fs/gfs2/log.c | 34 +++++++++++++++++-----------------
 1 file changed, 17 insertions(+), 17 deletions(-)

diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index 1ca5f2c468d5..f3b11bb78614 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -264,6 +264,23 @@ static void gfs2_log_update_head(struct gfs2_sbd *sdp)
 	sdp->sd_log_head = new_head;
 }
 
+/**
+ * gfs2_ail_empty_tr - empty one of the ail lists of a transaction
+ */
+
+static void gfs2_ail_empty_tr(struct gfs2_sbd *sdp, struct gfs2_trans *tr,
+			      struct list_head *head)
+{
+	struct gfs2_bufdata *bd;
+
+	while (!list_empty(head)) {
+		bd = list_first_entry(head, struct gfs2_bufdata,
+				      bd_ail_st_list);
+		gfs2_assert(sdp, bd->bd_tr == tr);
+		gfs2_remove_from_ail(bd);
+	}
+}
+
 /**
  * gfs2_ail1_empty_one - Check whether or not a trans in the AIL has been synced
  * @sdp: the filesystem
@@ -373,23 +390,6 @@ static void gfs2_ail1_wait(struct gfs2_sbd *sdp)
 	spin_unlock(&sdp->sd_ail_lock);
 }
 
-/**
- * gfs2_ail_empty_tr - empty one of the ail lists for a transaction
- */
-
-static void gfs2_ail_empty_tr(struct gfs2_sbd *sdp, struct gfs2_trans *tr,
-			      struct list_head *head)
-{
-	struct gfs2_bufdata *bd;
-
-	while (!list_empty(head)) {
-		bd = list_first_entry(head, struct gfs2_bufdata,
-				      bd_ail_st_list);
-		gfs2_assert(sdp, bd->bd_tr == tr);
-		gfs2_remove_from_ail(bd);
-	}
-}
-
 static void __ail2_empty(struct gfs2_sbd *sdp, struct gfs2_trans *tr)
 {
 	gfs2_ail_empty_tr(sdp, tr, &tr->tr_ail2_list);
-- 
2.26.2

[Cluster-devel] [PATCH v3 16/20] gfs2: No revokes for transactions at the tail of the log

[Andreas Gruenbacher]

In gfs2_log_flush, we're going through all active transactions.  For
each of the buffers in those transactions that has completed, we either
add a revoke to the active transaction immediately, or we move the
buffer to the transaction's ail2 list, which may result in a revoke
later.

However, whenever a transaction at the tail of the log completes, the
current tail of the log advances.  gfs2_log_flush writes out the log
header for the system transaction, with lh_tail set to that current tail
(sd_log_flush_head).  This implicitly revokes all previous blocks in the
log, so the revokes we've just written immediately become obsolete.
(This is not the case for transactions that haven't completed or aren't
at the tail of the log.)

Fix this by skipping completed transactions at the tail of the log
instead of writing revokes for them.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
 fs/gfs2/log.c | 30 ++++++++++++++++++++++++------
 1 file changed, 24 insertions(+), 6 deletions(-)

diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index f3b11bb78614..1fdc3b0dee5e 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -287,16 +287,34 @@ static void gfs2_ail_empty_tr(struct gfs2_sbd *sdp, struct gfs2_trans *tr,
  * @tr: the transaction
  * @max_revokes: If nonzero, issue revokes for the bd items for written buffers
  *
- * returns: the transaction's count of remaining active items
+ * Returns: true if the transaction has completed
  */
 
-static int gfs2_ail1_empty_one(struct gfs2_sbd *sdp, struct gfs2_trans *tr,
+static bool gfs2_ail1_empty_one(struct gfs2_sbd *sdp, struct gfs2_trans *tr,
 				int *max_revokes)
 {
 	struct gfs2_bufdata *bd, *s;
 	struct buffer_head *bh;
-	int active_count = 0;
+	bool empty;
 
+	if (!sdp->sd_log_error) {
+		empty = true;
+		list_for_each_entry_reverse(bd, &tr->tr_ail1_list, bd_ail_st_list) {
+			bh = bd->bd_bh;
+
+			if (buffer_busy(bh) || !list_empty(&bd->bd_list)) {
+				empty = false;
+				break;
+			}
+		}
+		if (empty) {
+			gfs2_ail_empty_tr(sdp, tr, &tr->tr_ail1_list);
+			gfs2_ail_empty_tr(sdp, tr, &tr->tr_ail2_list);
+			return empty;
+		}
+	}
+
+	empty = true;
 	list_for_each_entry_safe_reverse(bd, s, &tr->tr_ail1_list,
 					 bd_ail_st_list) {
 		bh = bd->bd_bh;
@@ -311,7 +329,7 @@ static int gfs2_ail1_empty_one(struct gfs2_sbd *sdp, struct gfs2_trans *tr,
 		 * for others.
 		 */
 		if (!sdp->sd_log_error && buffer_busy(bh)) {
-			active_count++;
+			empty = false;
 			continue;
 		}
 		if (!buffer_uptodate(bh) &&
@@ -332,7 +350,7 @@ static int gfs2_ail1_empty_one(struct gfs2_sbd *sdp, struct gfs2_trans *tr,
 		}
 		list_move(&bd->bd_ail_st_list, &tr->tr_ail2_list);
 	}
-	return active_count;
+	return empty;
 }
 
 /**
@@ -351,7 +369,7 @@ static int gfs2_ail1_empty(struct gfs2_sbd *sdp, int max_revokes)
 
 	spin_lock(&sdp->sd_ail_lock);
 	list_for_each_entry_safe_reverse(tr, s, &sdp->sd_ail1_list, tr_list) {
-		if (!gfs2_ail1_empty_one(sdp, tr, &max_revokes) && oldest_tr)
+		if (gfs2_ail1_empty_one(sdp, tr, &max_revokes) && oldest_tr)
 			list_move(&tr->tr_list, &sdp->sd_ail2_list);
 		else
 			oldest_tr = 0;
-- 
2.26.2

[Cluster-devel] [PATCH v3 17/20] gfs2: Remove sd_log_committed_revoke

[Andreas Gruenbacher]

In gfs2_trans_end -> gfs2_log_commit -> gfs2_log_refund, if we don't have a
system transaction, always attach the new transaction even if it only accounts
for revokes.  That way, tr_num_revoke - tr_num_revoke_rm in the system transaction
(sdp->sd_log_tr) will be the number of revokes committed so far, and we can use
that in calc_reserved instead.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
 fs/gfs2/incore.h |  1 -
 fs/gfs2/log.c    | 27 ++++++++++-----------------
 2 files changed, 10 insertions(+), 18 deletions(-)

diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
index fdf4d942bb1d..3589d02d1df9 100644
--- a/fs/gfs2/incore.h
+++ b/fs/gfs2/incore.h
@@ -820,7 +820,6 @@ struct gfs2_sbd {
 
 	struct gfs2_trans *sd_log_tr;
 	unsigned int sd_log_blks_reserved;
-	int sd_log_committed_revoke;
 
 	atomic_t sd_log_pinned;
 	unsigned int sd_log_num_revoke;
diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index 1fdc3b0dee5e..1ce4300aa81a 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -564,21 +564,15 @@ static inline unsigned int log_distance(struct gfs2_sbd *sdp, unsigned int newer
 static unsigned int calc_reserved(struct gfs2_sbd *sdp)
 {
 	unsigned int reserved = 0;
-	unsigned int mbuf;
-	unsigned int dbuf;
+	unsigned int blocks;
 	struct gfs2_trans *tr = sdp->sd_log_tr;
 
-	if (tr) {
-		mbuf = tr->tr_num_buf_new - tr->tr_num_buf_rm;
-		dbuf = tr->tr_num_databuf_new - tr->tr_num_databuf_rm;
-		reserved = mbuf + dbuf;
-		/* Account for header blocks */
-		reserved += DIV_ROUND_UP(mbuf, buf_limit(sdp));
-		reserved += DIV_ROUND_UP(dbuf, databuf_limit(sdp));
-	}
-
-	if (sdp->sd_log_committed_revoke > 0)
-		reserved += gfs2_struct2blk(sdp, sdp->sd_log_committed_revoke);
+	blocks = tr->tr_num_buf_new - tr->tr_num_buf_rm;
+	reserved += blocks + DIV_ROUND_UP(blocks, buf_limit(sdp));
+	blocks = tr->tr_num_databuf_new - tr->tr_num_databuf_rm;
+	reserved += blocks + DIV_ROUND_UP(blocks, databuf_limit(sdp));
+	if (tr->tr_num_revoke - tr->tr_num_revoke_rm)
+		reserved += gfs2_struct2blk(sdp, tr->tr_num_revoke - tr->tr_num_revoke_rm);
 	/* One for the overall header */
 	if (reserved)
 		reserved++;
@@ -997,7 +991,8 @@ void gfs2_log_flush(struct gfs2_sbd *sdp, struct gfs2_glock *gl, u32 flags)
 		if (gfs2_assert_withdraw_delayed(sdp, !sdp->sd_log_num_revoke))
 			goto out_withdraw;
 	if (gfs2_assert_withdraw_delayed(sdp,
-			sdp->sd_log_num_revoke == sdp->sd_log_committed_revoke))
+			sdp->sd_log_num_revoke ==
+			(tr ? tr->tr_num_revoke - tr->tr_num_revoke_rm : 0)))
 		goto out_withdraw;
 
 	gfs2_ordered_write(sdp);
@@ -1025,7 +1020,6 @@ void gfs2_log_flush(struct gfs2_sbd *sdp, struct gfs2_glock *gl, u32 flags)
 	gfs2_log_lock(sdp);
 	gfs2_log_update_head(sdp);
 	sdp->sd_log_blks_reserved = 0;
-	sdp->sd_log_committed_revoke = 0;
 
 	spin_lock(&sdp->sd_ail_lock);
 	if (tr && !list_empty(&tr->tr_ail1_list)) {
@@ -1116,12 +1110,11 @@ static void log_refund(struct gfs2_sbd *sdp, struct gfs2_trans *tr)
 
 	if (sdp->sd_log_tr) {
 		gfs2_merge_trans(sdp, tr);
-	} else if (tr->tr_num_buf_new || tr->tr_num_databuf_new) {
+	} else {
 		sdp->sd_log_tr = tr;
 		set_bit(TR_ATTACHED, &tr->tr_flags);
 	}
 
-	sdp->sd_log_committed_revoke += tr->tr_num_revoke - tr->tr_num_revoke_rm;
 	reserved = calc_reserved(sdp);
 	maxres = sdp->sd_log_blks_reserved + tr->tr_reserved;
 	gfs2_assert_withdraw(sdp, maxres >= reserved);
-- 
2.26.2

[Cluster-devel] [PATCH v3 18/20] gfs2: Remove sd_log_blks_reserved

[Andreas Gruenbacher]

Now that sdp->sd_log_tr is defined even when the transaction only
indicates revokes, tr_reserved is equivalent to sd_log_blks_reserved,
so we can remove it.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
 fs/gfs2/incore.h |  1 -
 fs/gfs2/log.c    | 21 ++++++++++-----------
 fs/gfs2/log.h    |  2 +-
 fs/gfs2/lops.c   |  2 +-
 4 files changed, 12 insertions(+), 14 deletions(-)

diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
index 3589d02d1df9..5d50c3695f17 100644
--- a/fs/gfs2/incore.h
+++ b/fs/gfs2/incore.h
@@ -819,7 +819,6 @@ struct gfs2_sbd {
 	spinlock_t sd_log_lock;
 
 	struct gfs2_trans *sd_log_tr;
-	unsigned int sd_log_blks_reserved;
 
 	atomic_t sd_log_pinned;
 	unsigned int sd_log_num_revoke;
diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index 1ce4300aa81a..34c8291c9131 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -703,6 +703,7 @@ void gfs2_glock_remove_revoke(struct gfs2_glock *gl)
 /**
  * gfs2_flush_revokes - Add as many revokes to the system transaction as we can
  * @sdp: The GFS2 superblock
+ * @tr: The transaction
  *
  * Our usual strategy is to defer writing revokes as much as we can in the hope
  * that we'll eventually overwrite the journal, which will make those revokes
@@ -712,7 +713,7 @@ void gfs2_glock_remove_revoke(struct gfs2_glock *gl)
  * been written back.  This will basically come at no cost now, and will save
  * us from having to keep track of those blocks on the AIL2 list later.
  */
-void gfs2_flush_revokes(struct gfs2_sbd *sdp)
+void gfs2_flush_revokes(struct gfs2_sbd *sdp, struct gfs2_trans *tr)
 {
 	/* number of revokes we still have room for */
 	unsigned int max_revokes;
@@ -727,7 +728,7 @@ void gfs2_flush_revokes(struct gfs2_sbd *sdp)
 		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) {
+		if (!tr) {
 			atomic_dec(&sdp->sd_log_blks_free);
 			trace_gfs2_log_blocks(sdp, -2);
 		} else {
@@ -739,7 +740,7 @@ void gfs2_flush_revokes(struct gfs2_sbd *sdp)
 
 	if (!sdp->sd_log_num_revoke) {
 		atomic_inc(&sdp->sd_log_blks_free);
-		if (!sdp->sd_log_blks_reserved) {
+		if (!tr) {
 			atomic_inc(&sdp->sd_log_blks_free);
 			trace_gfs2_log_blocks(sdp, 2);
 		} else {
@@ -1019,7 +1020,6 @@ void gfs2_log_flush(struct gfs2_sbd *sdp, struct gfs2_glock *gl, u32 flags)
 
 	gfs2_log_lock(sdp);
 	gfs2_log_update_head(sdp);
-	sdp->sd_log_blks_reserved = 0;
 
 	spin_lock(&sdp->sd_ail_lock);
 	if (tr && !list_empty(&tr->tr_ail1_list)) {
@@ -1084,6 +1084,7 @@ static void gfs2_merge_trans(struct gfs2_sbd *sdp, struct gfs2_trans *new)
 
 	WARN_ON_ONCE(!test_bit(TR_ATTACHED, &old->tr_flags));
 
+	old->tr_reserved	+= new->tr_reserved;
 	old->tr_num_buf_new	+= new->tr_num_buf_new;
 	old->tr_num_databuf_new	+= new->tr_num_databuf_new;
 	old->tr_num_buf_rm	+= new->tr_num_buf_rm;
@@ -1104,24 +1105,23 @@ static void log_refund(struct gfs2_sbd *sdp, struct gfs2_trans *tr)
 {
 	unsigned int reserved;
 	unsigned int unused;
-	unsigned int maxres;
 
 	gfs2_log_lock(sdp);
 
 	if (sdp->sd_log_tr) {
 		gfs2_merge_trans(sdp, tr);
+		tr = sdp->sd_log_tr;
 	} else {
 		sdp->sd_log_tr = tr;
 		set_bit(TR_ATTACHED, &tr->tr_flags);
 	}
 
-	reserved = calc_reserved(sdp);
-	maxres = sdp->sd_log_blks_reserved + tr->tr_reserved;
-	gfs2_assert_withdraw(sdp, maxres >= reserved);
-	unused = maxres - reserved;
+	reserved = tr->tr_reserved;
+	tr->tr_reserved = calc_reserved(sdp);
+	gfs2_assert_withdraw(sdp, reserved >= tr->tr_reserved);
+	unused = reserved - tr->tr_reserved;
 	if (unused)
 		gfs2_log_release(sdp, unused);
-	sdp->sd_log_blks_reserved = reserved;
 
 	gfs2_log_unlock(sdp);
 }
@@ -1159,7 +1159,6 @@ void gfs2_log_commit(struct gfs2_sbd *sdp, struct gfs2_trans *tr)
 
 static void gfs2_log_shutdown(struct gfs2_sbd *sdp)
 {
-	gfs2_assert_withdraw(sdp, !sdp->sd_log_blks_reserved);
 	gfs2_assert_withdraw(sdp, !sdp->sd_log_num_revoke);
 	gfs2_assert_withdraw(sdp, list_empty(&sdp->sd_ail1_list));
 
diff --git a/fs/gfs2/log.h b/fs/gfs2/log.h
index b36a3539f352..f3c8e4285ec9 100644
--- a/fs/gfs2/log.h
+++ b/fs/gfs2/log.h
@@ -81,6 +81,6 @@ extern void log_flush_wait(struct gfs2_sbd *sdp);
 extern int gfs2_logd(void *data);
 extern void gfs2_add_revoke(struct gfs2_sbd *sdp, struct gfs2_bufdata *bd);
 extern void gfs2_glock_remove_revoke(struct gfs2_glock *gl);
-extern void gfs2_flush_revokes(struct gfs2_sbd *sdp);
+extern void gfs2_flush_revokes(struct gfs2_sbd *sdp, struct gfs2_trans *tr);
 
 #endif /* __LOG_DOT_H__ */
diff --git a/fs/gfs2/lops.c b/fs/gfs2/lops.c
index 8658ebbcb4a9..db554f7623ec 100644
--- a/fs/gfs2/lops.c
+++ b/fs/gfs2/lops.c
@@ -845,7 +845,7 @@ static void revoke_lo_before_commit(struct gfs2_sbd *sdp, struct gfs2_trans *tr)
 	struct page *page;
 	unsigned int length;
 
-	gfs2_flush_revokes(sdp);
+	gfs2_flush_revokes(sdp, tr);
 	if (!sdp->sd_log_num_revoke)
 		return;
 
-- 
2.26.2

[Cluster-devel] [PATCH v3 19/20] gfs2: Rework the log space allocation logic

[Andreas Gruenbacher]

The current log space allocation logic is hard to understand or extend.
The principle it that when the log is flushed, we may or may not have a
transaction active that has space allocated in the log.  To deal with
that, we set aside a magical number of blocks to be used in case we
don't have an active transaction.  This pool of blocks is managed in a
haphazard way, and it's not clear that the pool will always be big
enough, though.  We can't easily return unused log space at the end of a
transaction; instead, the number of blocks allocated must match the
number of blocks used.

Simplify this as follows:
 * When transactions are allocated or merged, always reserve enough
   blocks to flush the transaction (err on the safe side).
 * In gfs2_log_flush, return any allocated blocks that haven't been used.
 * Maintain a pool of spare of blocks big enough to do one log flush, as
   before.
 * In gfs2_log_flush, when we have no active transaction, allocate a
   suitable number of blocks locally.  For that, use the spare pool when
   called from logd, and leave the pool alone otherwise.  This means
   that when the log is almost full, logd will still be able to do one
   more log flush, which will result in more log space becoming
   available.

This makes the log space allocator code much easier to work with in the
future.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
 fs/gfs2/log.c   | 152 ++++++++++++++++++++++++++++--------------------
 fs/gfs2/log.h   |   9 ++-
 fs/gfs2/lops.c  |   2 +-
 fs/gfs2/trans.c |   6 +-
 4 files changed, 100 insertions(+), 69 deletions(-)

diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index 34c8291c9131..c32c8d2d97e5 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -465,15 +465,42 @@ void gfs2_log_release(struct gfs2_sbd *sdp, unsigned int blks)
 }
 
 /**
- * gfs2_log_reserve - Make a log reservation
+ * __gfs2_log_try_reserve - Try to make a log reservation
  * @sdp: The GFS2 superblock
  * @blks: The number of blocks to reserve
+ * @taboo_blks: The number of blocks to leave free
  *
- * Note that we never give out the last few blocks of the journal. Thats
- * due to the fact that there is a small number of header blocks
- * associated with each log flush. The exact number can't be known until
- * flush time, so we ensure that we have just enough free blocks at all
- * times to avoid running out during a log flush.
+ * Try to do the same as __gfs2_log_reserve(), but fail if no more log
+ * space is immediately available.
+ */
+static bool __gfs2_log_try_reserve(struct gfs2_sbd *sdp, unsigned int blks,
+				   unsigned int taboo_blks)
+{
+	unsigned wanted = blks + taboo_blks;
+	unsigned int free_blocks;
+
+	free_blocks = atomic_read(&sdp->sd_log_blks_free);
+	while (free_blocks >= wanted) {
+		if (atomic_try_cmpxchg(&sdp->sd_log_blks_free, &free_blocks,
+				       free_blocks - blks)) {
+			trace_gfs2_log_blocks(sdp, -blks);
+			return true;
+		}
+	}
+	return false;
+}
+
+/**
+ * __gfs2_log_reserve - Make a log reservation
+ * @sdp: The GFS2 superblock
+ * @blks: The number of blocks to reserve
+ * @taboo_blks: The number of blocks to leave free
+ *
+ * @taboo_blks is set to 0 for logd, and to GFS2_LOG_FLUSH_MIN_BLOCKS
+ * for all other processes.  This ensures that when the log is almost full,
+ * logd will still be able to call gfs2_log_flush one more time  without
+ * blocking, which will advance the tail and make some more log space
+ * available.
  *
  * We no longer flush the log here, instead we wake up logd to do that
  * for us. To avoid the thundering herd and to ensure that we deal fairly
@@ -482,19 +509,12 @@ void gfs2_log_release(struct gfs2_sbd *sdp, unsigned int blks)
  * wake the next waiter on the list.
  */
 
-void gfs2_log_reserve(struct gfs2_sbd *sdp, unsigned int blks)
+static void __gfs2_log_reserve(struct gfs2_sbd *sdp, unsigned int blks,
+			       unsigned int taboo_blks)
 {
-	unsigned reserved_blks = 7 * (4096 / sdp->sd_vfs->s_blocksize);
-	unsigned wanted = blks + reserved_blks;
+	unsigned wanted = blks + taboo_blks;
 	unsigned int free_blocks;
 
-	free_blocks = atomic_read(&sdp->sd_log_blks_free);
-	while (free_blocks >= wanted) {
-		if (atomic_try_cmpxchg(&sdp->sd_log_blks_free, &free_blocks,
-				       free_blocks - blks))
-			return;
-	}
-
 	atomic_add(blks, &sdp->sd_log_blks_needed);
 	for (;;) {
 		if (current != sdp->sd_logd_process)
@@ -516,6 +536,19 @@ void gfs2_log_reserve(struct gfs2_sbd *sdp, unsigned int blks)
 		wake_up(&sdp->sd_log_waitq);
 }
 
+/**
+ * gfs2_log_reserve - Make a log reservation
+ * @sdp: The GFS2 superblock
+ * @blks: The number of blocks to reserve
+ */
+
+void gfs2_log_reserve(struct gfs2_sbd *sdp, unsigned int blks)
+{
+	if (__gfs2_log_try_reserve(sdp, blks, GFS2_LOG_FLUSH_MIN_BLOCKS))
+		return;
+	__gfs2_log_reserve(sdp, blks, GFS2_LOG_FLUSH_MIN_BLOCKS);
+}
+
 /**
  * log_distance - Compute distance between two journal blocks
  * @sdp: The GFS2 superblock
@@ -563,7 +596,7 @@ static inline unsigned int log_distance(struct gfs2_sbd *sdp, unsigned int newer
  */
 static unsigned int calc_reserved(struct gfs2_sbd *sdp)
 {
-	unsigned int reserved = 0;
+	unsigned int reserved = GFS2_LOG_FLUSH_MIN_BLOCKS;
 	unsigned int blocks;
 	struct gfs2_trans *tr = sdp->sd_log_tr;
 
@@ -572,10 +605,7 @@ static unsigned int calc_reserved(struct gfs2_sbd *sdp)
 	blocks = tr->tr_num_databuf_new - tr->tr_num_databuf_rm;
 	reserved += blocks + DIV_ROUND_UP(blocks, databuf_limit(sdp));
 	if (tr->tr_num_revoke - tr->tr_num_revoke_rm)
-		reserved += gfs2_struct2blk(sdp, tr->tr_num_revoke - tr->tr_num_revoke_rm);
-	/* One for the overall header */
-	if (reserved)
-		reserved++;
+		reserved += gfs2_struct2blk(sdp, tr->tr_num_revoke - tr->tr_num_revoke_rm) - 1;
 	return reserved;
 }
 
@@ -703,7 +733,6 @@ void gfs2_glock_remove_revoke(struct gfs2_glock *gl)
 /**
  * gfs2_flush_revokes - Add as many revokes to the system transaction as we can
  * @sdp: The GFS2 superblock
- * @tr: The transaction
  *
  * Our usual strategy is to defer writing revokes as much as we can in the hope
  * that we'll eventually overwrite the journal, which will make those revokes
@@ -713,7 +742,7 @@ void gfs2_glock_remove_revoke(struct gfs2_glock *gl)
  * been written back.  This will basically come at no cost now, and will save
  * us from having to keep track of those blocks on the AIL2 list later.
  */
-void gfs2_flush_revokes(struct gfs2_sbd *sdp, struct gfs2_trans *tr)
+void gfs2_flush_revokes(struct gfs2_sbd *sdp)
 {
 	/* number of revokes we still have room for */
 	unsigned int max_revokes;
@@ -724,29 +753,8 @@ void gfs2_flush_revokes(struct gfs2_sbd *sdp, struct gfs2_trans *tr)
 		max_revokes += roundup(sdp->sd_log_num_revoke - sdp->sd_ldptrs,
 				       sdp->sd_inptrs);
 	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 (!tr) {
-			atomic_dec(&sdp->sd_log_blks_free);
-			trace_gfs2_log_blocks(sdp, -2);
-		} else {
-			trace_gfs2_log_blocks(sdp, -1);
-		}
-	}
 	gfs2_ail1_empty(sdp, max_revokes);
 	gfs2_log_unlock(sdp);
-
-	if (!sdp->sd_log_num_revoke) {
-		atomic_inc(&sdp->sd_log_blks_free);
-		if (!tr) {
-			atomic_inc(&sdp->sd_log_blks_free);
-			trace_gfs2_log_blocks(sdp, 2);
-		} else {
-			trace_gfs2_log_blocks(sdp, 1);
-		}
-	}
 }
 
 /**
@@ -859,6 +867,7 @@ static void log_write_header(struct gfs2_sbd *sdp, u32 flags)
 	gfs2_log_incr_head(sdp);
 	log_flush_wait(sdp);
 	log_pull_tail(sdp);
+	gfs2_log_update_head(sdp);
 }
 
 /**
@@ -958,10 +967,14 @@ static void trans_drain(struct gfs2_trans *tr)
 void gfs2_log_flush(struct gfs2_sbd *sdp, struct gfs2_glock *gl, u32 flags)
 {
 	struct gfs2_trans *tr = NULL;
+	unsigned int reserved_blocks = 0, used_blocks = 0;
 	enum gfs2_freeze_state state = atomic_read(&sdp->sd_freeze_state);
+	unsigned int first_log_head;
 
 	down_write(&sdp->sd_log_flush_lock);
+	trace_gfs2_log_flush(sdp, 1, flags);
 
+repeat:
 	/*
 	 * Do this check while holding the log_flush_lock to prevent new
 	 * buffers from being added to the ail via gfs2_pin()
@@ -972,22 +985,39 @@ void gfs2_log_flush(struct gfs2_sbd *sdp, struct gfs2_glock *gl, u32 flags)
 	/* Log might have been flushed while we waited for the flush lock */
 	if (gl && !test_bit(GLF_LFLUSH, &gl->gl_flags))
 		goto out;
-	trace_gfs2_log_flush(sdp, 1, flags);
 
-	if (flags & GFS2_LOG_HEAD_FLUSH_SHUTDOWN)
-		clear_bit(SDF_JOURNAL_LIVE, &sdp->sd_flags);
+	first_log_head = sdp->sd_log_head;
+	sdp->sd_log_flush_head = first_log_head;
 
-	sdp->sd_log_flush_head = sdp->sd_log_head;
 	tr = sdp->sd_log_tr;
 	if (tr) {
+		if (reserved_blocks)
+			gfs2_log_release(sdp, reserved_blocks);
+		reserved_blocks = tr->tr_reserved;
 		sdp->sd_log_tr = NULL;
-		tr->tr_first = sdp->sd_log_flush_head;
+		tr->tr_first = first_log_head;
 		if (unlikely (state == SFS_FROZEN))
 			if (gfs2_assert_withdraw_delayed(sdp,
 			       !tr->tr_num_buf_new && !tr->tr_num_databuf_new))
 				goto out_withdraw;
+	} else if (!reserved_blocks) {
+		unsigned int taboo_blocks = GFS2_LOG_FLUSH_MIN_BLOCKS;
+
+		reserved_blocks = GFS2_LOG_FLUSH_MIN_BLOCKS;
+		if (current == sdp->sd_logd_process)
+			taboo_blocks = 0;
+
+		if (!__gfs2_log_try_reserve(sdp, reserved_blocks, taboo_blocks)) {
+			up_write(&sdp->sd_log_flush_lock);
+			__gfs2_log_reserve(sdp, reserved_blocks, taboo_blocks);
+			down_write(&sdp->sd_log_flush_lock);
+			goto repeat;
+		}
 	}
 
+	if (flags & GFS2_LOG_HEAD_FLUSH_SHUTDOWN)
+		clear_bit(SDF_JOURNAL_LIVE, &sdp->sd_flags);
+
 	if (unlikely(state == SFS_FROZEN))
 		if (gfs2_assert_withdraw_delayed(sdp, !sdp->sd_log_num_revoke))
 			goto out_withdraw;
@@ -1010,8 +1040,6 @@ void gfs2_log_flush(struct gfs2_sbd *sdp, struct gfs2_glock *gl, u32 flags)
 		log_flush_wait(sdp);
 		log_write_header(sdp, flags);
 	} else if (sdp->sd_log_tail != sdp->sd_log_flush_tail && !sdp->sd_log_idle) {
-		atomic_dec(&sdp->sd_log_blks_free); /* Adjust for unreserved buffer */
-		trace_gfs2_log_blocks(sdp, -1);
 		log_write_header(sdp, flags);
 	}
 	if (gfs2_withdrawn(sdp))
@@ -1019,8 +1047,6 @@ void gfs2_log_flush(struct gfs2_sbd *sdp, struct gfs2_glock *gl, u32 flags)
 	lops_after_commit(sdp, tr);
 
 	gfs2_log_lock(sdp);
-	gfs2_log_update_head(sdp);
-
 	spin_lock(&sdp->sd_ail_lock);
 	if (tr && !list_empty(&tr->tr_ail1_list)) {
 		list_add(&tr->tr_list, &sdp->sd_ail1_list);
@@ -1034,10 +1060,7 @@ void gfs2_log_flush(struct gfs2_sbd *sdp, struct gfs2_glock *gl, u32 flags)
 			empty_ail1_list(sdp);
 			if (gfs2_withdrawn(sdp))
 				goto out_withdraw;
-			atomic_dec(&sdp->sd_log_blks_free); /* Adjust for unreserved buffer */
-			trace_gfs2_log_blocks(sdp, -1);
 			log_write_header(sdp, flags);
-			gfs2_log_update_head(sdp);
 		}
 		if (flags & (GFS2_LOG_HEAD_FLUSH_SHUTDOWN |
 			     GFS2_LOG_HEAD_FLUSH_FREEZE))
@@ -1047,12 +1070,17 @@ void gfs2_log_flush(struct gfs2_sbd *sdp, struct gfs2_glock *gl, u32 flags)
 	}
 
 out_end:
-	trace_gfs2_log_flush(sdp, 0, flags);
+	used_blocks = log_distance(sdp, sdp->sd_log_flush_head, first_log_head);
+	if (gfs2_assert_withdraw_delayed(sdp, used_blocks <= reserved_blocks))
+		goto out;
 out:
+	if (used_blocks != reserved_blocks)
+		gfs2_log_release(sdp, reserved_blocks - used_blocks);
 	up_write(&sdp->sd_log_flush_lock);
 	gfs2_trans_free(sdp, tr);
 	if (gfs2_withdrawing(sdp))
 		gfs2_withdraw(sdp);
+	trace_gfs2_log_flush(sdp, 0, flags);
 	return;
 
 out_withdraw:
@@ -1162,15 +1190,11 @@ static void gfs2_log_shutdown(struct gfs2_sbd *sdp)
 	gfs2_assert_withdraw(sdp, !sdp->sd_log_num_revoke);
 	gfs2_assert_withdraw(sdp, list_empty(&sdp->sd_ail1_list));
 
-	sdp->sd_log_flush_head = sdp->sd_log_head;
-
 	log_write_header(sdp, GFS2_LOG_HEAD_UNMOUNT | GFS2_LFC_SHUTDOWN);
+	log_pull_tail(sdp);
 
 	gfs2_assert_warn(sdp, sdp->sd_log_head == sdp->sd_log_tail);
 	gfs2_assert_warn(sdp, list_empty(&sdp->sd_ail2_list));
-
-	gfs2_log_update_head(sdp);
-	sdp->sd_log_tail = sdp->sd_log_head;
 }
 
 static inline int gfs2_jrnl_flush_reqd(struct gfs2_sbd *sdp)
@@ -1225,7 +1249,7 @@ int gfs2_logd(void *data)
 		if (gfs2_jrnl_flush_reqd(sdp) || t == 0) {
 			gfs2_ail1_empty(sdp, 0);
 			gfs2_log_flush(sdp, NULL, GFS2_LOG_HEAD_FLUSH_NORMAL |
-				       GFS2_LFC_LOGD_JFLUSH_REQD);
+						  GFS2_LFC_LOGD_JFLUSH_REQD);
 		}
 
 		if (gfs2_ail_flush_reqd(sdp)) {
@@ -1233,7 +1257,7 @@ int gfs2_logd(void *data)
 			gfs2_ail1_wait(sdp);
 			gfs2_ail1_empty(sdp, 0);
 			gfs2_log_flush(sdp, NULL, GFS2_LOG_HEAD_FLUSH_NORMAL |
-				       GFS2_LFC_LOGD_AIL_FLUSH_REQD);
+						  GFS2_LFC_LOGD_AIL_FLUSH_REQD);
 		}
 
 		t = gfs2_tune_get(sdp, gt_logd_secs) * HZ;
diff --git a/fs/gfs2/log.h b/fs/gfs2/log.h
index f3c8e4285ec9..e7f4a8d6be64 100644
--- a/fs/gfs2/log.h
+++ b/fs/gfs2/log.h
@@ -13,6 +13,13 @@
 #include "incore.h"
 #include "inode.h"
 
+/*
+ * The minimum amount of log space required for a log flush is one block for
+ * revokes and one block for the log header.  Log flushes other than
+ * GFS2_LOG_HEAD_FLUSH_NORMAL may write one or two more log headers.
+ */
+#define GFS2_LOG_FLUSH_MIN_BLOCKS 4
+
 /**
  * gfs2_log_lock - acquire the right to mess with the log manager
  * @sdp: the filesystem
@@ -81,6 +88,6 @@ extern void log_flush_wait(struct gfs2_sbd *sdp);
 extern int gfs2_logd(void *data);
 extern void gfs2_add_revoke(struct gfs2_sbd *sdp, struct gfs2_bufdata *bd);
 extern void gfs2_glock_remove_revoke(struct gfs2_glock *gl);
-extern void gfs2_flush_revokes(struct gfs2_sbd *sdp, struct gfs2_trans *tr);
+extern void gfs2_flush_revokes(struct gfs2_sbd *sdp);
 
 #endif /* __LOG_DOT_H__ */
diff --git a/fs/gfs2/lops.c b/fs/gfs2/lops.c
index db554f7623ec..8658ebbcb4a9 100644
--- a/fs/gfs2/lops.c
+++ b/fs/gfs2/lops.c
@@ -845,7 +845,7 @@ static void revoke_lo_before_commit(struct gfs2_sbd *sdp, struct gfs2_trans *tr)
 	struct page *page;
 	unsigned int length;
 
-	gfs2_flush_revokes(sdp, tr);
+	gfs2_flush_revokes(sdp);
 	if (!sdp->sd_log_num_revoke)
 		return;
 
diff --git a/fs/gfs2/trans.c b/fs/gfs2/trans.c
index 3675e92f2857..0f936e3bcd90 100644
--- a/fs/gfs2/trans.c
+++ b/fs/gfs2/trans.c
@@ -59,7 +59,7 @@ int __gfs2_trans_begin(struct gfs2_sbd *sdp, unsigned int blocks,
 	tr->tr_ip = _RET_IP_;
 	tr->tr_blocks = blocks;
 	tr->tr_revokes = revokes;
-	tr->tr_reserved = 1;
+	tr->tr_reserved = GFS2_LOG_FLUSH_MIN_BLOCKS;
 	if (blocks) {
 		/*
 		 * The reserved blocks are either used for data or metadata.
@@ -69,7 +69,7 @@ int __gfs2_trans_begin(struct gfs2_sbd *sdp, unsigned int blocks,
 		tr->tr_reserved += blocks + 1 + DIV_ROUND_UP(blocks - 1, databuf_limit(sdp));
 	}
 	if (revokes)
-		tr->tr_reserved += gfs2_struct2blk(sdp, revokes);
+		tr->tr_reserved += gfs2_struct2blk(sdp, revokes) - 1;
 	INIT_LIST_HEAD(&tr->tr_databuf);
 	INIT_LIST_HEAD(&tr->tr_buf);
 	INIT_LIST_HEAD(&tr->tr_list);
@@ -117,8 +117,8 @@ void gfs2_trans_end(struct gfs2_sbd *sdp)
 	current->journal_info = NULL;
 
 	if (!test_bit(TR_TOUCHED, &tr->tr_flags)) {
-		gfs2_log_release(sdp, tr->tr_reserved);
 		up_read(&sdp->sd_log_flush_lock);
+		gfs2_log_release(sdp, tr->tr_reserved);
 		sb_end_intwrite(sdp->sd_vfs);
 		gfs2_trans_free(sdp, tr);
 		return;
-- 
2.26.2

[Cluster-devel] [PATCH v3 20/20] gfs2: Per-revoke accounting in transactions

[Andreas Gruenbacher]

In the log, revokes are stored as a revoke descriptor (struct
gfs2_log_descriptor), followed by zero or more additional revoke blocks
(struct gfs2_meta_header).  On filesystems with a blocksize of 4k, the
revoke descriptor contains up to 503 revokes, and the metadata blocks
contain up to 509 revokes each.  We've so far been reserving space for revokes
in transactions in block granularity, so a lot more space than needed was
being allocated and then released again.

This patch switches to assigning revokes to transactions individually instead.
Initially, space for the revoke descriptor is reserved and handed out to
transactions.  When more revokes than that are reserved, additional revoke
blocks are added.  When the log is flushed, the space for the additional revoke
blocks is released, but we never release the revoke descriptor block.

Transactions may still reserve more revokes than they will actually need in the
end, but now we won't overshoot the target as much, and by only returning the
space for excess revokes at log flush time, we further reduce the amount of
contention between processes.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
 fs/gfs2/glops.c      |   8 +---
 fs/gfs2/incore.h     |   2 +-
 fs/gfs2/log.c        | 112 ++++++++++++++++++++++++++++++++++---------
 fs/gfs2/log.h        |   6 ++-
 fs/gfs2/lops.c       |   1 -
 fs/gfs2/ops_fstype.c |   7 +++
 fs/gfs2/trans.c      |  31 +++++++++---
 7 files changed, 129 insertions(+), 38 deletions(-)

diff --git a/fs/gfs2/glops.c b/fs/gfs2/glops.c
index 853e590ccc15..daafe9d781a3 100644
--- a/fs/gfs2/glops.c
+++ b/fs/gfs2/glops.c
@@ -131,19 +131,15 @@ void gfs2_ail_flush(struct gfs2_glock *gl, bool fsync)
 {
 	struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
 	unsigned int revokes = atomic_read(&gl->gl_ail_count);
-	unsigned int max_revokes = (sdp->sd_sb.sb_bsize - sizeof(struct gfs2_log_descriptor)) / sizeof(u64);
 	int ret;
 
 	if (!revokes)
 		return;
 
-	while (revokes > max_revokes)
-		max_revokes += (sdp->sd_sb.sb_bsize - sizeof(struct gfs2_meta_header)) / sizeof(u64);
-
-	ret = gfs2_trans_begin(sdp, 0, max_revokes);
+	ret = gfs2_trans_begin(sdp, 0, revokes);
 	if (ret)
 		return;
-	__gfs2_ail_flush(gl, fsync, max_revokes);
+	__gfs2_ail_flush(gl, fsync, revokes);
 	gfs2_trans_end(sdp);
 	gfs2_log_flush(sdp, NULL, GFS2_LOG_HEAD_FLUSH_NORMAL |
 		       GFS2_LFC_AIL_FLUSH);
diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
index 5d50c3695f17..a045e6ffecf0 100644
--- a/fs/gfs2/incore.h
+++ b/fs/gfs2/incore.h
@@ -505,7 +505,6 @@ struct gfs2_trans {
 	unsigned int tr_num_buf_rm;
 	unsigned int tr_num_databuf_rm;
 	unsigned int tr_num_revoke;
-	unsigned int tr_num_revoke_rm;
 
 	struct list_head tr_list;
 	struct list_head tr_databuf;
@@ -831,6 +830,7 @@ struct gfs2_sbd {
 	atomic_t sd_log_thresh2;
 	atomic_t sd_log_blks_free;
 	atomic_t sd_log_blks_needed;
+	atomic_t sd_log_revokes_available;
 	wait_queue_head_t sd_log_waitq;
 	wait_queue_head_t sd_logd_waitq;
 
diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index c32c8d2d97e5..c68e05508435 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -447,6 +447,32 @@ bool gfs2_log_is_empty(struct gfs2_sbd *sdp) {
 	return atomic_read(&sdp->sd_log_blks_free) == sdp->sd_jdesc->jd_blocks;
 }
 
+static bool __gfs2_log_try_reserve_revokes(struct gfs2_sbd *sdp, unsigned int revokes)
+{
+	unsigned int available;
+
+	available = atomic_read(&sdp->sd_log_revokes_available);
+	while (available >= revokes) {
+		if (atomic_try_cmpxchg(&sdp->sd_log_revokes_available,
+				       &available, available - revokes))
+			return true;
+	}
+	return false;
+}
+
+/**
+ * gfs2_log_release_revokes - Release a given number of revokes
+ * @sdp: The GFS2 superblock
+ * @revokes: The number of revokes to release
+ *
+ * sdp->sd_log_flush_lock must be held.
+ */
+void gfs2_log_release_revokes(struct gfs2_sbd *sdp, unsigned int revokes)
+{
+	if (revokes)
+		atomic_add(revokes, &sdp->sd_log_revokes_available);
+}
+
 /**
  * gfs2_log_release - Release a given number of log blocks
  * @sdp: The GFS2 superblock
@@ -537,15 +563,59 @@ static void __gfs2_log_reserve(struct gfs2_sbd *sdp, unsigned int blks,
 }
 
 /**
- * gfs2_log_reserve - Make a log reservation
+ * gfs2_log_try_reserve - Try to make a log reservation
  * @sdp: The GFS2 superblock
- * @blks: The number of blocks to reserve
+ * @tr: The transaction
+ * @extra_revokes: The number of additional revokes reserved (output)
+ *
+ * This is similar to gfs2_log_reserve, but sdp->sd_log_flush_lock must be
+ * held for correct revoke accounting.
  */
 
-void gfs2_log_reserve(struct gfs2_sbd *sdp, unsigned int blks)
+bool gfs2_log_try_reserve(struct gfs2_sbd *sdp, struct gfs2_trans *tr,
+			  unsigned int *extra_revokes)
 {
+	unsigned int blks = tr->tr_reserved;
+	unsigned int revokes = tr->tr_revokes;
+	unsigned int revoke_blks = 0;
+
+	*extra_revokes = 0;
+	if (revokes && !__gfs2_log_try_reserve_revokes(sdp, revokes)) {
+		revoke_blks = DIV_ROUND_UP(revokes, sdp->sd_inptrs);
+		*extra_revokes = revoke_blks * sdp->sd_inptrs - revokes;
+		blks += revoke_blks;
+	}
+	if (!blks)
+		return true;
 	if (__gfs2_log_try_reserve(sdp, blks, GFS2_LOG_FLUSH_MIN_BLOCKS))
-		return;
+		return true;
+	if (!revoke_blks)
+		gfs2_log_release_revokes(sdp, revokes);
+	return false;
+}
+
+/**
+ * gfs2_log_reserve - Make a log reservation
+ * @sdp: The GFS2 superblock
+ * @tr: The transaction
+ * @extra_revokes: The number of additional revokes reserved (output)
+ *
+ * sdp->sd_log_flush_lock must not be held.
+ */
+
+void gfs2_log_reserve(struct gfs2_sbd *sdp, struct gfs2_trans *tr,
+		      unsigned int *extra_revokes)
+{
+	unsigned int blks = tr->tr_reserved;
+	unsigned int revokes = tr->tr_revokes;
+	unsigned int revoke_blks = 0;
+
+	*extra_revokes = 0;
+	if (revokes) {
+		revoke_blks = DIV_ROUND_UP(revokes, sdp->sd_inptrs);
+		*extra_revokes = revoke_blks * sdp->sd_inptrs - revokes;
+		blks += revoke_blks;
+	}
 	__gfs2_log_reserve(sdp, blks, GFS2_LOG_FLUSH_MIN_BLOCKS);
 }
 
@@ -604,8 +674,6 @@ static unsigned int calc_reserved(struct gfs2_sbd *sdp)
 	reserved += blocks + DIV_ROUND_UP(blocks, buf_limit(sdp));
 	blocks = tr->tr_num_databuf_new - tr->tr_num_databuf_rm;
 	reserved += blocks + DIV_ROUND_UP(blocks, databuf_limit(sdp));
-	if (tr->tr_num_revoke - tr->tr_num_revoke_rm)
-		reserved += gfs2_struct2blk(sdp, tr->tr_num_revoke - tr->tr_num_revoke_rm) - 1;
 	return reserved;
 }
 
@@ -745,14 +813,9 @@ void gfs2_glock_remove_revoke(struct gfs2_glock *gl)
 void gfs2_flush_revokes(struct gfs2_sbd *sdp)
 {
 	/* number of revokes we still have room for */
-	unsigned int max_revokes;
+	unsigned int max_revokes = atomic_read(&sdp->sd_log_revokes_available);
 
 	gfs2_log_lock(sdp);
-	max_revokes = sdp->sd_ldptrs;
-	if (sdp->sd_log_num_revoke > sdp->sd_ldptrs)
-		max_revokes += roundup(sdp->sd_log_num_revoke - sdp->sd_ldptrs,
-				       sdp->sd_inptrs);
-	max_revokes -= sdp->sd_log_num_revoke;
 	gfs2_ail1_empty(sdp, max_revokes);
 	gfs2_log_unlock(sdp);
 }
@@ -970,6 +1033,7 @@ void gfs2_log_flush(struct gfs2_sbd *sdp, struct gfs2_glock *gl, u32 flags)
 	unsigned int reserved_blocks = 0, used_blocks = 0;
 	enum gfs2_freeze_state state = atomic_read(&sdp->sd_freeze_state);
 	unsigned int first_log_head;
+	unsigned int reserved_revokes = 0;
 
 	down_write(&sdp->sd_log_flush_lock);
 	trace_gfs2_log_flush(sdp, 1, flags);
@@ -996,10 +1060,12 @@ void gfs2_log_flush(struct gfs2_sbd *sdp, struct gfs2_glock *gl, u32 flags)
 		reserved_blocks = tr->tr_reserved;
 		sdp->sd_log_tr = NULL;
 		tr->tr_first = first_log_head;
-		if (unlikely (state == SFS_FROZEN))
+		if (unlikely (state == SFS_FROZEN)) {
 			if (gfs2_assert_withdraw_delayed(sdp,
 			       !tr->tr_num_buf_new && !tr->tr_num_databuf_new))
 				goto out_withdraw;
+		}
+		reserved_revokes = sdp->sd_log_num_revoke;
 	} else if (!reserved_blocks) {
 		unsigned int taboo_blocks = GFS2_LOG_FLUSH_MIN_BLOCKS;
 
@@ -1013,18 +1079,15 @@ void gfs2_log_flush(struct gfs2_sbd *sdp, struct gfs2_glock *gl, u32 flags)
 			down_write(&sdp->sd_log_flush_lock);
 			goto repeat;
 		}
+		BUG_ON(sdp->sd_log_num_revoke);
 	}
 
 	if (flags & GFS2_LOG_HEAD_FLUSH_SHUTDOWN)
 		clear_bit(SDF_JOURNAL_LIVE, &sdp->sd_flags);
 
 	if (unlikely(state == SFS_FROZEN))
-		if (gfs2_assert_withdraw_delayed(sdp, !sdp->sd_log_num_revoke))
+		if (gfs2_assert_withdraw_delayed(sdp, !reserved_revokes))
 			goto out_withdraw;
-	if (gfs2_assert_withdraw_delayed(sdp,
-			sdp->sd_log_num_revoke ==
-			(tr ? tr->tr_num_revoke - tr->tr_num_revoke_rm : 0)))
-		goto out_withdraw;
 
 	gfs2_ordered_write(sdp);
 	if (gfs2_withdrawn(sdp))
@@ -1071,11 +1134,16 @@ void gfs2_log_flush(struct gfs2_sbd *sdp, struct gfs2_glock *gl, u32 flags)
 
 out_end:
 	used_blocks = log_distance(sdp, sdp->sd_log_flush_head, first_log_head);
-	if (gfs2_assert_withdraw_delayed(sdp, used_blocks <= reserved_blocks))
-		goto out;
+	reserved_revokes += atomic_read(&sdp->sd_log_revokes_available);
+	atomic_set(&sdp->sd_log_revokes_available, sdp->sd_ldptrs);
+	gfs2_assert_withdraw(sdp, reserved_revokes % sdp->sd_inptrs == sdp->sd_ldptrs);
+	if (reserved_revokes > sdp->sd_ldptrs)
+		reserved_blocks += (reserved_revokes - sdp->sd_ldptrs) / sdp->sd_inptrs;
 out:
-	if (used_blocks != reserved_blocks)
+	if (used_blocks != reserved_blocks) {
+		gfs2_assert_withdraw_delayed(sdp, used_blocks < reserved_blocks);
 		gfs2_log_release(sdp, reserved_blocks - used_blocks);
+	}
 	up_write(&sdp->sd_log_flush_lock);
 	gfs2_trans_free(sdp, tr);
 	if (gfs2_withdrawing(sdp))
@@ -1117,8 +1185,8 @@ static void gfs2_merge_trans(struct gfs2_sbd *sdp, struct gfs2_trans *new)
 	old->tr_num_databuf_new	+= new->tr_num_databuf_new;
 	old->tr_num_buf_rm	+= new->tr_num_buf_rm;
 	old->tr_num_databuf_rm	+= new->tr_num_databuf_rm;
+	old->tr_revokes		+= new->tr_revokes;
 	old->tr_num_revoke	+= new->tr_num_revoke;
-	old->tr_num_revoke_rm	+= new->tr_num_revoke_rm;
 
 	list_splice_tail_init(&new->tr_databuf, &old->tr_databuf);
 	list_splice_tail_init(&new->tr_buf, &old->tr_buf);
diff --git a/fs/gfs2/log.h b/fs/gfs2/log.h
index e7f4a8d6be64..eea58015710e 100644
--- a/fs/gfs2/log.h
+++ b/fs/gfs2/log.h
@@ -74,8 +74,12 @@ extern void gfs2_ordered_del_inode(struct gfs2_inode *ip);
 extern unsigned int gfs2_struct2blk(struct gfs2_sbd *sdp, unsigned int nstruct);
 extern void gfs2_remove_from_ail(struct gfs2_bufdata *bd);
 extern bool gfs2_log_is_empty(struct gfs2_sbd *sdp);
+extern void gfs2_log_release_revokes(struct gfs2_sbd *sdp, unsigned int revokes);
 extern void gfs2_log_release(struct gfs2_sbd *sdp, unsigned int blks);
-extern void gfs2_log_reserve(struct gfs2_sbd *sdp, unsigned int blks);
+extern bool gfs2_log_try_reserve(struct gfs2_sbd *sdp, struct gfs2_trans *tr,
+				 unsigned int *extra_revokes);
+extern void gfs2_log_reserve(struct gfs2_sbd *sdp, struct gfs2_trans *tr,
+			     unsigned int *extra_revokes);
 extern void gfs2_write_log_header(struct gfs2_sbd *sdp, struct gfs2_jdesc *jd,
 				  u64 seq, u32 tail, u32 lblock, u32 flags,
 				  int op_flags);
diff --git a/fs/gfs2/lops.c b/fs/gfs2/lops.c
index 8658ebbcb4a9..dfe8537cb88e 100644
--- a/fs/gfs2/lops.c
+++ b/fs/gfs2/lops.c
@@ -857,7 +857,6 @@ static void revoke_lo_before_commit(struct gfs2_sbd *sdp, struct gfs2_trans *tr)
 		sdp->sd_log_num_revoke--;
 
 		if (offset + sizeof(u64) > sdp->sd_sb.sb_bsize) {
-
 			gfs2_log_write_page(sdp, page);
 			page = mempool_alloc(gfs2_page_pool, GFP_NOIO);
 			mh = page_address(page);
diff --git a/fs/gfs2/ops_fstype.c b/fs/gfs2/ops_fstype.c
index 986dc2ebebf0..316ca5fc99e8 100644
--- a/fs/gfs2/ops_fstype.c
+++ b/fs/gfs2/ops_fstype.c
@@ -315,6 +315,13 @@ static int gfs2_read_sb(struct gfs2_sbd *sdp, int silent)
 				     sizeof(struct gfs2_meta_header))
 		* GFS2_NBBY; /* not the rgrp bitmap, subsequent bitmaps only */
 
+	/*
+	 * We always keep at least one block reserved for revokes in
+	 * transactions.  This greatly simplifies allocating additional
+	 * revoke blocks.
+	 */
+	atomic_set(&sdp->sd_log_revokes_available, sdp->sd_ldptrs);
+
 	/* Compute maximum reservation required to add a entry to a directory */
 
 	hash_blocks = DIV_ROUND_UP(sizeof(u64) * BIT(GFS2_DIR_MAX_DEPTH),
diff --git a/fs/gfs2/trans.c b/fs/gfs2/trans.c
index 0f936e3bcd90..c7aa1c1d795d 100644
--- a/fs/gfs2/trans.c
+++ b/fs/gfs2/trans.c
@@ -31,15 +31,16 @@ static void gfs2_print_trans(struct gfs2_sbd *sdp, const struct gfs2_trans *tr)
 	fs_warn(sdp, "blocks=%u revokes=%u reserved=%u touched=%u\n",
 		tr->tr_blocks, tr->tr_revokes, tr->tr_reserved,
 		test_bit(TR_TOUCHED, &tr->tr_flags));
-	fs_warn(sdp, "Buf %u/%u Databuf %u/%u Revoke %u/%u\n",
+	fs_warn(sdp, "Buf %u/%u Databuf %u/%u Revoke %u\n",
 		tr->tr_num_buf_new, tr->tr_num_buf_rm,
 		tr->tr_num_databuf_new, tr->tr_num_databuf_rm,
-		tr->tr_num_revoke, tr->tr_num_revoke_rm);
+		tr->tr_num_revoke);
 }
 
 int __gfs2_trans_begin(struct gfs2_sbd *sdp, unsigned int blocks,
 		       unsigned int revokes, gfp_t gfp_mask)
 {
+	unsigned int extra_revokes;
 	struct gfs2_trans *tr;
 	int error;
 
@@ -68,8 +69,6 @@ int __gfs2_trans_begin(struct gfs2_sbd *sdp, unsigned int blocks,
 		 */
 		tr->tr_reserved += blocks + 1 + DIV_ROUND_UP(blocks - 1, databuf_limit(sdp));
 	}
-	if (revokes)
-		tr->tr_reserved += gfs2_struct2blk(sdp, revokes) - 1;
 	INIT_LIST_HEAD(&tr->tr_databuf);
 	INIT_LIST_HEAD(&tr->tr_buf);
 	INIT_LIST_HEAD(&tr->tr_list);
@@ -83,10 +82,26 @@ int __gfs2_trans_begin(struct gfs2_sbd *sdp, unsigned int blocks,
 
 	sb_start_intwrite(sdp->sd_vfs);
 
-	gfs2_log_reserve(sdp, tr->tr_reserved);
+	/*
+	 * Try the reservations under sd_log_flush_lock to prevent log flushes
+	 * from creating inconsistencies between the number of allocated and
+	 * reserved revokes.  If that fails, do a full-block allocation outside
+	 * of the lock to avoid stalling log flushes.  Then, allot the
+	 * appropriate number of blocks to revokes, use as many revokes locally
+	 * as needed, and "release" the surplus into the revokes pool.
+	 */
 
 	down_read(&sdp->sd_log_flush_lock);
+	if (gfs2_log_try_reserve(sdp, tr, &extra_revokes))
+		goto reserved;
+	up_read(&sdp->sd_log_flush_lock);
+	gfs2_log_reserve(sdp, tr, &extra_revokes);
+	down_read(&sdp->sd_log_flush_lock);
+
+reserved:
+	gfs2_log_release_revokes(sdp, extra_revokes);
 	if (unlikely(!test_bit(SDF_JOURNAL_LIVE, &sdp->sd_flags))) {
+		gfs2_log_release_revokes(sdp, tr->tr_revokes);
 		up_read(&sdp->sd_log_flush_lock);
 		gfs2_log_release(sdp, tr->tr_reserved);
 		sb_end_intwrite(sdp->sd_vfs);
@@ -117,6 +132,7 @@ void gfs2_trans_end(struct gfs2_sbd *sdp)
 	current->journal_info = NULL;
 
 	if (!test_bit(TR_TOUCHED, &tr->tr_flags)) {
+		gfs2_log_release_revokes(sdp, tr->tr_revokes);
 		up_read(&sdp->sd_log_flush_lock);
 		gfs2_log_release(sdp, tr->tr_reserved);
 		sb_end_intwrite(sdp->sd_vfs);
@@ -124,6 +140,8 @@ void gfs2_trans_end(struct gfs2_sbd *sdp)
 		return;
 	}
 
+	gfs2_log_release_revokes(sdp, tr->tr_revokes - tr->tr_num_revoke);
+
 	nbuf = tr->tr_num_buf_new + tr->tr_num_databuf_new;
 	nbuf -= tr->tr_num_buf_rm;
 	nbuf -= tr->tr_num_databuf_rm;
@@ -280,7 +298,6 @@ void gfs2_trans_add_revoke(struct gfs2_sbd *sdp, struct gfs2_bufdata *bd)
 void gfs2_trans_remove_revoke(struct gfs2_sbd *sdp, u64 blkno, unsigned int len)
 {
 	struct gfs2_bufdata *bd, *tmp;
-	struct gfs2_trans *tr = current->journal_info;
 	unsigned int n = len;
 
 	gfs2_log_lock(sdp);
@@ -292,7 +309,7 @@ void gfs2_trans_remove_revoke(struct gfs2_sbd *sdp, u64 blkno, unsigned int len)
 			if (bd->bd_gl)
 				gfs2_glock_remove_revoke(bd->bd_gl);
 			kmem_cache_free(gfs2_bufdata_cachep, bd);
-			tr->tr_num_revoke_rm++;
+			gfs2_log_release_revokes(sdp, 1);
 			if (--n == 0)
 				break;
 		}
-- 
2.26.2