linux-kernel - [PATCH 3.12 072/123] dm space map metadata: fix occasional leak of a metadata block on resize

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Message-Id: <bffa4ad0e0cab954d70b99dbfcfb7f02ce7c6fc7.1438699154.git.jslaby@suse.cz>
Date:	Tue,  4 Aug 2015 16:40:16 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, Joe Thornber <ejt@...hat.com>,
	Mike Snitzer <snitzer@...hat.com>, Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 072/123] dm space map metadata: fix occasional leak of a metadata block on resize

From: Joe Thornber <ejt@...hat.com>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit 6096d91af0b65a3967139b32d5adbb3647858a26 upstream.

The metadata space map has a simplified 'bootstrap' mode that is
operational when extending the space maps.  Whilst in this mode it's
possible for some refcount decrement operations to become queued (eg, as
a result of shadowing one of the bitmap indexes).  These decrements were
not being applied when switching out of bootstrap mode.

The effect of this bug was the leaking of a 4k metadata block.  This is
detected by the latest version of thin_check as a non fatal error.

Signed-off-by: Joe Thornber <ejt@...hat.com>
Signed-off-by: Mike Snitzer <snitzer@...hat.com>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 drivers/md/persistent-data/dm-space-map-metadata.c | 50 +++++++++++++++-------
 1 file changed, 35 insertions(+), 15 deletions(-)

diff --git a/drivers/md/persistent-data/dm-space-map-metadata.c b/drivers/md/persistent-data/dm-space-map-metadata.c
index d9a5aa532017..f6dea401232c 100644
--- a/drivers/md/persistent-data/dm-space-map-metadata.c
+++ b/drivers/md/persistent-data/dm-space-map-metadata.c
@@ -204,6 +204,27 @@ static void in(struct sm_metadata *smm)
 	smm->recursion_count++;
 }
 
+static int apply_bops(struct sm_metadata *smm)
+{
+	int r = 0;
+
+	while (!brb_empty(&smm->uncommitted)) {
+		struct block_op bop;
+
+		r = brb_pop(&smm->uncommitted, &bop);
+		if (r) {
+			DMERR("bug in bop ring buffer");
+			break;
+		}
+
+		r = commit_bop(smm, &bop);
+		if (r)
+			break;
+	}
+
+	return r;
+}
+
 static int out(struct sm_metadata *smm)
 {
 	int r = 0;
@@ -216,21 +237,8 @@ static int out(struct sm_metadata *smm)
 		return -ENOMEM;
 	}
 
-	if (smm->recursion_count == 1) {
-		while (!brb_empty(&smm->uncommitted)) {
-			struct block_op bop;
-
-			r = brb_pop(&smm->uncommitted, &bop);
-			if (r) {
-				DMERR("bug in bop ring buffer");
-				break;
-			}
-
-			r = commit_bop(smm, &bop);
-			if (r)
-				break;
-		}
-	}
+	if (smm->recursion_count == 1)
+		apply_bops(smm);
 
 	smm->recursion_count--;
 
@@ -702,6 +710,12 @@ static int sm_metadata_extend(struct dm_space_map *sm, dm_block_t extra_blocks)
 		}
 		old_len = smm->begin;
 
+		r = apply_bops(smm);
+		if (r) {
+			DMERR("%s: apply_bops failed", __func__);
+			goto out;
+		}
+
 		r = sm_ll_commit(&smm->ll);
 		if (r)
 			goto out;
@@ -769,6 +783,12 @@ int dm_sm_metadata_create(struct dm_space_map *sm,
 	if (r)
 		return r;
 
+	r = apply_bops(smm);
+	if (r) {
+		DMERR("%s: apply_bops failed", __func__);
+		return r;
+	}
+
 	return sm_metadata_commit(sm);
 }
 
-- 
2.5.0

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