ocfs2: retry on ENOSPC if sufficient space in truncate log

The testcase "mmaptruncate" in ocfs2 test suite always fails with ENOSPC
error on small volume (say less than 10G).  This testcase repeatedly
performs "extend" and "truncate" on a file.  Continuously, it truncates
the file to 1/2 of the size, and then extends to 100% of the size.  The
main bitmap will quickly run out of space because the "truncate" code
prevent truncate log from being flushed by
ocfs2_schedule_truncate_log_flush(osb, 1), while truncate log may have
cached lots of clusters.

So retry to allocate after flushing truncate log when ENOSPC is
returned.  And we cannot reuse the deleted blocks before the transaction
committed.  Fortunately, we already have a function to do this -
ocfs2_try_to_free_truncate_log().  Just need to remove the "static"
modifier and put it into the right place.

The "unlock"/"lock" code isn't elegant, but there seems to be no better
option.

[zren@suse.com: locking fix]
  Link: http://lkml.kernel.org/r/1468031546-4797-1-git-send-email-zren@suse.com
Link: http://lkml.kernel.org/r/1466586469-5541-1-git-send-email-zren@suse.com
Signed-off-by: Eric Ren <zren@suse.com>
Reviewed-by: Gang He <ghe@suse.com>
Reviewed-by: Joseph Qi <joseph.qi@huawei.com>
Reviewed-by: Mark Fasheh <mfasheh@suse.de>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 19 insertions, 1 deletions

diff --git a/fs/ocfs2/suballoc.c b/fs/ocfs2/suballoc.c
index 2f19aeec5482..ea47120a85ff 100644
--- a/fs/ocfs2/suballoc.c
+++ b/fs/ocfs2/suballoc.c
@@ -1164,7 +1164,8 @@ static int ocfs2_reserve_clusters_with_limit(struct ocfs2_super *osb,
 					     int flags,
 					     struct ocfs2_alloc_context **ac)
 {
-	int status;
+	int status, ret = 0;
+	int retried = 0;
 
 	*ac = kzalloc(sizeof(struct ocfs2_alloc_context), GFP_KERNEL);
 	if (!(*ac)) {
@@ -1189,7 +1190,24 @@ static int ocfs2_reserve_clusters_with_limit(struct ocfs2_super *osb,
 	}
 
 	if (status == -ENOSPC) {
+retry:
 		status = ocfs2_reserve_cluster_bitmap_bits(osb, *ac);
+		/* Retry if there is sufficient space cached in truncate log */
+		if (status == -ENOSPC && !retried) {
+			retried = 1;
+			ocfs2_inode_unlock((*ac)->ac_inode, 1);
+			inode_unlock((*ac)->ac_inode);
+
+			ret = ocfs2_try_to_free_truncate_log(osb, bits_wanted);
+			if (ret == 1)
+				goto retry;
+
+			if (ret < 0)
+				mlog_errno(ret);
+
+			inode_lock((*ac)->ac_inode);
+			ocfs2_inode_lock((*ac)->ac_inode, NULL, 1);
+		}
 		if (status < 0) {
 			if (status != -ENOSPC)
 				mlog_errno(status);