Do not allow a cache device to use a metadata device that is already
in use by another cache device.
Add list member to the cache structure. Also reorder members in the
cache structure to eliminate 6 out of 7 holes (reclaiming 24 bytes).
Example:
echo "0 8192 linear 253:1 0" | dmsetup create metadata
echo "0 2097152 linear 253:1 8192" | dmsetup create ssd
echo "0 33554432 linear 253:0 0" | dmsetup create origin
echo "0 33554432 cache /dev/mapper/metadata /dev/mapper/ssd /dev/mapper/origin 512 0 default 0" | dmsetup create cache1
echo "0 33554432 cache /dev/mapper/metadata /dev/mapper/ssd /dev/mapper/origin 512 0 default 0" | dmsetup create cache2
device-mapper: reload ioctl on cache2 failed: Device or resource busy
Command failed
Kernel log shows:
device-mapper: table: 253:8: cache: metadata device already in use by a cache
device-mapper: ioctl: error adding target to table
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
---
drivers/md/dm-cache-target.c | 95 +++++++++++++++++++++++++++++++++++-------
1 files changed, 80 insertions(+), 15 deletions(-)
diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c
index 0df3ec0..77b3629 100644
--- a/drivers/md/dm-cache-target.c
+++ b/drivers/md/dm-cache-target.c
@@ -101,6 +101,8 @@ struct cache {
struct dm_target *ti;
struct dm_target_callbacks callbacks;
+ struct dm_cache_metadata *cmd;
+
/*
* Metadata is written to this device.
*/
@@ -117,11 +119,6 @@ struct cache {
struct dm_dev *cache_dev;
/*
- * Cache features such as write-through.
- */
- struct cache_features features;
-
- /*
* Size of the origin device in _complete_ blocks and native sectors.
*/
dm_oblock_t origin_blocks;
@@ -138,8 +135,6 @@ struct cache {
uint32_t sectors_per_block;
int sectors_per_block_shift;
- struct dm_cache_metadata *cmd;
-
spinlock_t lock;
struct bio_list deferred_bios;
struct bio_list deferred_flush_bios;
@@ -148,8 +143,8 @@ struct cache {
struct list_head completed_migrations;
struct list_head need_commit_migrations;
sector_t migration_threshold;
- atomic_t nr_migrations;
wait_queue_head_t migration_wait;
+ atomic_t nr_migrations;
/*
* cache_size entries, dirty if set
@@ -160,9 +155,16 @@ struct cache {
/*
* origin_blocks entries, discarded if set.
*/
- uint32_t discard_block_size; /* a power of 2 times sectors per block */
dm_dblock_t discard_nr_blocks;
unsigned long *discard_bitset;
+ uint32_t discard_block_size; /* a power of 2 times sectors per block */
+
+ /*
+ * Rather than reconstructing the table line for the status we just
+ * save it and regurgitate.
+ */
+ unsigned nr_ctr_args;
+ const char **ctr_args;
struct dm_kcopyd_client *copier;
struct workqueue_struct *wq;
@@ -187,14 +189,14 @@ struct cache {
bool loaded_mappings:1;
bool loaded_discards:1;
- struct cache_stats stats;
-
/*
- * Rather than reconstructing the table line for the status we just
- * save it and regurgitate.
+ * Cache features such as write-through.
*/
- unsigned nr_ctr_args;
- const char **ctr_args;
+ struct cache_features features;
+
+ struct cache_stats stats;
+
+ struct list_head list;
};
struct per_bio_data {
@@ -231,6 +233,52 @@ struct dm_cache_migration {
struct dm_bio_prison_cell *new_ocell;
};
+/*----------------------------------------------------------------*/
+
+/*
+ * A global list of caches that uses the metadata block_device as a key.
+ */
+static struct dm_cache_table {
+ struct mutex mutex;
+ struct list_head caches;
+} dm_cache_table;
+
+static void cache_table_init(void)
+{
+ mutex_init(&dm_cache_table.mutex);
+ INIT_LIST_HEAD(&dm_cache_table.caches);
+}
+
+static void __cache_table_insert(struct cache *cache)
+{
+ BUG_ON(!mutex_is_locked(&dm_cache_table.mutex));
+ list_add(&cache->list, &dm_cache_table.caches);
+}
+
+static void __cache_table_remove(struct cache *cache)
+{
+ BUG_ON(!mutex_is_locked(&dm_cache_table.mutex));
+ list_del(&cache->list);
+}
+
+static struct cache *__cache_table_lookup(struct block_device *md_dev)
+{
+ struct cache *cache = NULL, *tmp;
+
+ BUG_ON(!mutex_is_locked(&dm_cache_table.mutex));
+
+ list_for_each_entry(tmp, &dm_cache_table.caches, list) {
+ if (tmp->metadata_dev->bdev == md_dev) {
+ cache = tmp;
+ break;
+ }
+ }
+
+ return cache;
+}
+
+/*----------------------------------------------------------------*/
+
/*
* Processing a bio in the worker thread may require these memory
* allocations. We prealloc to avoid deadlocks (the same worker thread
@@ -1533,6 +1581,10 @@ static void cache_dtr(struct dm_target *ti)
{
struct cache *cache = ti->private;
+ mutex_lock(&dm_cache_table.mutex);
+ __cache_table_remove(cache);
+ mutex_unlock(&dm_cache_table.mutex);
+
destroy(cache);
}
@@ -2134,6 +2186,17 @@ static int cache_ctr(struct dm_target *ti, unsigned argc, char **argv)
goto out;
}
+ mutex_lock(&dm_cache_table.mutex);
+ if (__cache_table_lookup(cache->metadata_dev->bdev)) {
+ ti->error = "metadata device already in use by a cache";
+ r = -EBUSY;
+ mutex_unlock(&dm_cache_table.mutex);
+ destroy(cache);
+ goto out;
+ }
+ __cache_table_insert(cache);
+ mutex_unlock(&dm_cache_table.mutex);
+
ti->private = cache;
out:
@@ -2639,6 +2702,8 @@ static int __init dm_cache_init(void)
{
int r;
+ cache_table_init();
+
r = dm_register_target(&cache_target);
if (r) {
DMERR("cache target registration failed: %d", r);
--
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