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Message-Id: <1424305990-17983-103-git-send-email-kamal@canonical.com>
Date: Wed, 18 Feb 2015 16:33:09 -0800
From: Kamal Mostafa <kamal@...onical.com>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org,
kernel-team@...ts.ubuntu.com
Cc: Joe Thornber <ejt@...hat.com>, Mike Snitzer <snitzer@...hat.com>,
Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.13.y-ckt 102/103] dm cache: share cache-metadata object across inactive and active DM tables
3.13.11-ckt16 -stable review patch. If anyone has any objections, please let me know.
------------------
From: Joe Thornber <ejt@...hat.com>
commit 9b1cc9f251affdd27f29fe46d0989ba76c33faf6 upstream.
If a DM table is reloaded with an inactive table when the device is not
suspended (normal procedure for LVM2), then there will be two dm-bufio
objects that can diverge. This can lead to a situation where the
inactive table uses bufio to read metadata at the same time the active
table writes metadata -- resulting in the inactive table having stale
metadata buffers once it is promoted to the active table slot.
Fix this by using reference counting and a global list of cache metadata
objects to ensure there is only one metadata object per metadata device.
Signed-off-by: Joe Thornber <ejt@...hat.com>
Signed-off-by: Mike Snitzer <snitzer@...hat.com>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
drivers/md/dm-cache-metadata.c | 101 ++++++++++++++++++++++++++++++++++++++---
1 file changed, 95 insertions(+), 6 deletions(-)
diff --git a/drivers/md/dm-cache-metadata.c b/drivers/md/dm-cache-metadata.c
index a87d3fa..d290e83 100644
--- a/drivers/md/dm-cache-metadata.c
+++ b/drivers/md/dm-cache-metadata.c
@@ -94,6 +94,9 @@ struct cache_disk_superblock {
} __packed;
struct dm_cache_metadata {
+ atomic_t ref_count;
+ struct list_head list;
+
struct block_device *bdev;
struct dm_block_manager *bm;
struct dm_space_map *metadata_sm;
@@ -669,10 +672,10 @@ static void unpack_value(__le64 value_le, dm_oblock_t *block, unsigned *flags)
/*----------------------------------------------------------------*/
-struct dm_cache_metadata *dm_cache_metadata_open(struct block_device *bdev,
- sector_t data_block_size,
- bool may_format_device,
- size_t policy_hint_size)
+static struct dm_cache_metadata *metadata_open(struct block_device *bdev,
+ sector_t data_block_size,
+ bool may_format_device,
+ size_t policy_hint_size)
{
int r;
struct dm_cache_metadata *cmd;
@@ -683,6 +686,7 @@ struct dm_cache_metadata *dm_cache_metadata_open(struct block_device *bdev,
return NULL;
}
+ atomic_set(&cmd->ref_count, 1);
init_rwsem(&cmd->root_lock);
cmd->bdev = bdev;
cmd->data_block_size = data_block_size;
@@ -705,10 +709,95 @@ struct dm_cache_metadata *dm_cache_metadata_open(struct block_device *bdev,
return cmd;
}
+/*
+ * We keep a little list of ref counted metadata objects to prevent two
+ * different target instances creating separate bufio instances. This is
+ * an issue if a table is reloaded before the suspend.
+ */
+static DEFINE_MUTEX(table_lock);
+static LIST_HEAD(table);
+
+static struct dm_cache_metadata *lookup(struct block_device *bdev)
+{
+ struct dm_cache_metadata *cmd;
+
+ list_for_each_entry(cmd, &table, list)
+ if (cmd->bdev == bdev) {
+ atomic_inc(&cmd->ref_count);
+ return cmd;
+ }
+
+ return NULL;
+}
+
+static struct dm_cache_metadata *lookup_or_open(struct block_device *bdev,
+ sector_t data_block_size,
+ bool may_format_device,
+ size_t policy_hint_size)
+{
+ struct dm_cache_metadata *cmd, *cmd2;
+
+ mutex_lock(&table_lock);
+ cmd = lookup(bdev);
+ mutex_unlock(&table_lock);
+
+ if (cmd)
+ return cmd;
+
+ cmd = metadata_open(bdev, data_block_size, may_format_device, policy_hint_size);
+ if (cmd) {
+ mutex_lock(&table_lock);
+ cmd2 = lookup(bdev);
+ if (cmd2) {
+ mutex_unlock(&table_lock);
+ __destroy_persistent_data_objects(cmd);
+ kfree(cmd);
+ return cmd2;
+ }
+ list_add(&cmd->list, &table);
+ mutex_unlock(&table_lock);
+ }
+
+ return cmd;
+}
+
+static bool same_params(struct dm_cache_metadata *cmd, sector_t data_block_size)
+{
+ if (cmd->data_block_size != data_block_size) {
+ DMERR("data_block_size (%llu) different from that in metadata (%llu)\n",
+ (unsigned long long) data_block_size,
+ (unsigned long long) cmd->data_block_size);
+ return false;
+ }
+
+ return true;
+}
+
+struct dm_cache_metadata *dm_cache_metadata_open(struct block_device *bdev,
+ sector_t data_block_size,
+ bool may_format_device,
+ size_t policy_hint_size)
+{
+ struct dm_cache_metadata *cmd = lookup_or_open(bdev, data_block_size,
+ may_format_device, policy_hint_size);
+ if (cmd && !same_params(cmd, data_block_size)) {
+ dm_cache_metadata_close(cmd);
+ return NULL;
+ }
+
+ return cmd;
+}
+
void dm_cache_metadata_close(struct dm_cache_metadata *cmd)
{
- __destroy_persistent_data_objects(cmd);
- kfree(cmd);
+ if (atomic_dec_and_test(&cmd->ref_count)) {
+ mutex_lock(&table_lock);
+ list_del(&cmd->list);
+ mutex_unlock(&table_lock);
+
+ __destroy_persistent_data_objects(cmd);
+ kfree(cmd);
+ }
}
/*
--
1.9.1
--
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