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-rw-r--r--drivers/md/dm-snap.c107
-rw-r--r--drivers/md/dm-snap.h9
2 files changed, 106 insertions, 10 deletions
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index 1ba8a47d61b..de302702ab3 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -40,6 +40,11 @@
*/
#define SNAPSHOT_PAGES (((1UL << 20) >> PAGE_SHIFT) ? : 1)
+/*
+ * The size of the mempool used to track chunks in use.
+ */
+#define MIN_IOS 256
+
static struct workqueue_struct *ksnapd;
static void flush_queued_bios(struct work_struct *work);
@@ -93,6 +98,42 @@ static struct kmem_cache *exception_cache;
static struct kmem_cache *pending_cache;
static mempool_t *pending_pool;
+struct dm_snap_tracked_chunk {
+ struct hlist_node node;
+ chunk_t chunk;
+};
+
+static struct kmem_cache *tracked_chunk_cache;
+
+static struct dm_snap_tracked_chunk *track_chunk(struct dm_snapshot *s,
+ chunk_t chunk)
+{
+ struct dm_snap_tracked_chunk *c = mempool_alloc(s->tracked_chunk_pool,
+ GFP_NOIO);
+ unsigned long flags;
+
+ c->chunk = chunk;
+
+ spin_lock_irqsave(&s->tracked_chunk_lock, flags);
+ hlist_add_head(&c->node,
+ &s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)]);
+ spin_unlock_irqrestore(&s->tracked_chunk_lock, flags);
+
+ return c;
+}
+
+static void stop_tracking_chunk(struct dm_snapshot *s,
+ struct dm_snap_tracked_chunk *c)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&s->tracked_chunk_lock, flags);
+ hlist_del(&c->node);
+ spin_unlock_irqrestore(&s->tracked_chunk_lock, flags);
+
+ mempool_free(c, s->tracked_chunk_pool);
+}
+
/*
* One of these per registered origin, held in the snapshot_origins hash
*/
@@ -482,6 +523,7 @@ static int set_chunk_size(struct dm_snapshot *s, const char *chunk_size_arg,
static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
{
struct dm_snapshot *s;
+ int i;
int r = -EINVAL;
char persistent;
char *origin_path;
@@ -564,11 +606,24 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
goto bad5;
}
+ s->tracked_chunk_pool = mempool_create_slab_pool(MIN_IOS,
+ tracked_chunk_cache);
+ if (!s->tracked_chunk_pool) {
+ ti->error = "Could not allocate tracked_chunk mempool for "
+ "tracking reads";
+ goto bad6;
+ }
+
+ for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
+ INIT_HLIST_HEAD(&s->tracked_chunk_hash[i]);
+
+ spin_lock_init(&s->tracked_chunk_lock);
+
/* Metadata must only be loaded into one table at once */
r = s->store.read_metadata(&s->store);
if (r < 0) {
ti->error = "Failed to read snapshot metadata";
- goto bad6;
+ goto bad_load_and_register;
} else if (r > 0) {
s->valid = 0;
DMWARN("Snapshot is marked invalid.");
@@ -582,7 +637,7 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
if (register_snapshot(s)) {
r = -EINVAL;
ti->error = "Cannot register snapshot origin";
- goto bad6;
+ goto bad_load_and_register;
}
ti->private = s;
@@ -590,6 +645,9 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
return 0;
+ bad_load_and_register:
+ mempool_destroy(s->tracked_chunk_pool);
+
bad6:
dm_kcopyd_client_destroy(s->kcopyd_client);
@@ -624,6 +682,9 @@ static void __free_exceptions(struct dm_snapshot *s)
static void snapshot_dtr(struct dm_target *ti)
{
+#ifdef CONFIG_DM_DEBUG
+ int i;
+#endif
struct dm_snapshot *s = ti->private;
flush_workqueue(ksnapd);
@@ -632,6 +693,13 @@ static void snapshot_dtr(struct dm_target *ti)
/* After this returns there can be no new kcopyd jobs. */
unregister_snapshot(s);
+#ifdef CONFIG_DM_DEBUG
+ for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
+ BUG_ON(!hlist_empty(&s->tracked_chunk_hash[i]));
+#endif
+
+ mempool_destroy(s->tracked_chunk_pool);
+
__free_exceptions(s);
dm_put_device(ti, s->origin);
@@ -974,14 +1042,10 @@ static int snapshot_map(struct dm_target *ti, struct bio *bio,
start_copy(pe);
goto out;
}
- } else
- /*
- * FIXME: this read path scares me because we
- * always use the origin when we have a pending
- * exception. However I can't think of a
- * situation where this is wrong - ejt.
- */
+ } else {
bio->bi_bdev = s->origin->bdev;
+ map_context->ptr = track_chunk(s, chunk);
+ }
out_unlock:
up_write(&s->lock);
@@ -989,6 +1053,18 @@ static int snapshot_map(struct dm_target *ti, struct bio *bio,
return r;
}
+static int snapshot_end_io(struct dm_target *ti, struct bio *bio,
+ int error, union map_info *map_context)
+{
+ struct dm_snapshot *s = ti->private;
+ struct dm_snap_tracked_chunk *c = map_context->ptr;
+
+ if (c)
+ stop_tracking_chunk(s, c);
+
+ return 0;
+}
+
static void snapshot_resume(struct dm_target *ti)
{
struct dm_snapshot *s = ti->private;
@@ -1266,6 +1342,7 @@ static struct target_type snapshot_target = {
.ctr = snapshot_ctr,
.dtr = snapshot_dtr,
.map = snapshot_map,
+ .end_io = snapshot_end_io,
.resume = snapshot_resume,
.status = snapshot_status,
};
@@ -1306,11 +1383,18 @@ static int __init dm_snapshot_init(void)
goto bad4;
}
+ tracked_chunk_cache = KMEM_CACHE(dm_snap_tracked_chunk, 0);
+ if (!tracked_chunk_cache) {
+ DMERR("Couldn't create cache to track chunks in use.");
+ r = -ENOMEM;
+ goto bad5;
+ }
+
pending_pool = mempool_create_slab_pool(128, pending_cache);
if (!pending_pool) {
DMERR("Couldn't create pending pool.");
r = -ENOMEM;
- goto bad5;
+ goto bad_pending_pool;
}
ksnapd = create_singlethread_workqueue("ksnapd");
@@ -1324,6 +1408,8 @@ static int __init dm_snapshot_init(void)
bad6:
mempool_destroy(pending_pool);
+ bad_pending_pool:
+ kmem_cache_destroy(tracked_chunk_cache);
bad5:
kmem_cache_destroy(pending_cache);
bad4:
@@ -1355,6 +1441,7 @@ static void __exit dm_snapshot_exit(void)
mempool_destroy(pending_pool);
kmem_cache_destroy(pending_cache);
kmem_cache_destroy(exception_cache);
+ kmem_cache_destroy(tracked_chunk_cache);
}
/* Module hooks */
diff --git a/drivers/md/dm-snap.h b/drivers/md/dm-snap.h
index 24f9fb73b98..70dc961f40d 100644
--- a/drivers/md/dm-snap.h
+++ b/drivers/md/dm-snap.h
@@ -130,6 +130,10 @@ struct exception_store {
void *context;
};
+#define DM_TRACKED_CHUNK_HASH_SIZE 16
+#define DM_TRACKED_CHUNK_HASH(x) ((unsigned long)(x) & \
+ (DM_TRACKED_CHUNK_HASH_SIZE - 1))
+
struct dm_snapshot {
struct rw_semaphore lock;
struct dm_target *ti;
@@ -174,6 +178,11 @@ struct dm_snapshot {
/* Queue of snapshot writes for ksnapd to flush */
struct bio_list queued_bios;
struct work_struct queued_bios_work;
+
+ /* Chunks with outstanding reads */
+ mempool_t *tracked_chunk_pool;
+ spinlock_t tracked_chunk_lock;
+ struct hlist_head tracked_chunk_hash[DM_TRACKED_CHUNK_HASH_SIZE];
};
/*
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-19 16:28:38 +0000