*/
#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);
*/
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);
+}
+
+static int __chunk_is_tracked(struct dm_snapshot *s, chunk_t chunk)
+{
+ struct dm_snap_tracked_chunk *c;
+ struct hlist_node *hn;
+ int found = 0;
+
+ spin_lock_irq(&s->tracked_chunk_lock);
+
+ hlist_for_each_entry(c, hn,
+ &s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)], node) {
+ if (c->chunk == chunk) {
+ found = 1;
+ break;
+ }
+ }
+
+ spin_unlock_irq(&s->tracked_chunk_lock);
+
+ return found;
+}
/*
* One of these per registered origin, held in the snapshot_origins hash
kmem_cache_free(exception_cache, e);
}
-static struct dm_snap_pending_exception *alloc_pending_exception(void)
+static struct dm_snap_pending_exception *alloc_pending_exception(struct dm_snapshot *s)
{
- return mempool_alloc(pending_pool, GFP_NOIO);
+ struct dm_snap_pending_exception *pe = mempool_alloc(s->pending_pool,
+ GFP_NOIO);
+
+ pe->snap = s;
+
+ return pe;
}
static void free_pending_exception(struct dm_snap_pending_exception *pe)
{
- mempool_free(pe, pending_pool);
+ mempool_free(pe, pe->snap->pending_pool);
}
static void insert_completed_exception(struct dm_snapshot *s,
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;
s->valid = 1;
s->active = 0;
- s->last_percent = 0;
init_rwsem(&s->lock);
spin_lock_init(&s->pe_lock);
s->ti = ti;
goto bad5;
}
+ s->pending_pool = mempool_create_slab_pool(MIN_IOS, pending_cache);
+ if (!s->pending_pool) {
+ ti->error = "Could not allocate mempool for pending exceptions";
+ goto bad6;
+ }
+
+ 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 bad_tracked_chunk_pool;
+ }
+
+ 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.");
if (register_snapshot(s)) {
r = -EINVAL;
ti->error = "Cannot register snapshot origin";
- goto bad6;
+ goto bad_load_and_register;
}
ti->private = s;
return 0;
+ bad_load_and_register:
+ mempool_destroy(s->tracked_chunk_pool);
+
+ bad_tracked_chunk_pool:
+ mempool_destroy(s->pending_pool);
+
bad6:
dm_kcopyd_client_destroy(s->kcopyd_client);
static void snapshot_dtr(struct dm_target *ti)
{
+#ifdef CONFIG_DM_DEBUG
+ int i;
+#endif
struct dm_snapshot *s = ti->private;
flush_workqueue(ksnapd);
/* 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);
+ mempool_destroy(s->pending_pool);
+
dm_put_device(ti, s->origin);
dm_put_device(ti, s->cow);
* the bios for the original write to the origin.
*/
if (primary_pe &&
- atomic_dec_and_test(&primary_pe->ref_count))
+ atomic_dec_and_test(&primary_pe->ref_count)) {
origin_bios = bio_list_get(&primary_pe->origin_bios);
+ free_pending_exception(primary_pe);
+ }
/*
* Free the pe if it's not linked to an origin write or if
if (!primary_pe || primary_pe != pe)
free_pending_exception(pe);
- /*
- * Free the primary pe if nothing references it.
- */
- if (primary_pe && !atomic_read(&primary_pe->ref_count))
- free_pending_exception(primary_pe);
-
return origin_bios;
}
goto out;
}
+ /*
+ * Check for conflicting reads. This is extremely improbable,
+ * so yield() is sufficient and there is no need for a wait queue.
+ */
+ while (__chunk_is_tracked(s, pe->e.old_chunk))
+ yield();
+
/*
* Add a proper exception, and remove the
* in-flight exception from the list.
* to hold the lock while we do this.
*/
up_write(&s->lock);
- pe = alloc_pending_exception();
+ pe = alloc_pending_exception(s);
down_write(&s->lock);
if (!s->valid) {
bio_list_init(&pe->snapshot_bios);
pe->primary_pe = NULL;
atomic_set(&pe->ref_count, 0);
- pe->snap = s;
pe->started = 0;
if (s->store.prepare_exception(&s->store, &pe->e)) {
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);
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;
.ctr = snapshot_ctr,
.dtr = snapshot_dtr,
.map = snapshot_map,
+ .end_io = snapshot_end_io,
.resume = snapshot_resume,
.status = snapshot_status,
};
goto bad4;
}
- pending_pool = mempool_create_slab_pool(128, pending_cache);
- if (!pending_pool) {
- DMERR("Couldn't create pending pool.");
+ 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;
}
if (!ksnapd) {
DMERR("Failed to create ksnapd workqueue.");
r = -ENOMEM;
- goto bad6;
+ goto bad_pending_pool;
}
return 0;
- bad6:
- mempool_destroy(pending_pool);
+ bad_pending_pool:
+ kmem_cache_destroy(tracked_chunk_cache);
bad5:
kmem_cache_destroy(pending_cache);
bad4:
DMERR("origin unregister failed %d", r);
exit_origin_hash();
- mempool_destroy(pending_pool);
kmem_cache_destroy(pending_cache);
kmem_cache_destroy(exception_cache);
+ kmem_cache_destroy(tracked_chunk_cache);
}
/* Module hooks */
projects / linux-2.6-omap-h63xx.git / blobdiff