struct bio_list snapshot_bios;
/*
- * Other pending_exceptions that are processing this
- * chunk. When this list is empty, we know we can
- * complete the origins.
+ * Short-term queue of pending exceptions prior to submission.
*/
- struct list_head siblings;
+ struct list_head list;
+
+ /*
+ * The primary pending_exception is the one that holds
+ * the sibling_count and the list of origin_bios for a
+ * group of pending_exceptions. It is always last to get freed.
+ * These fields get set up when writing to the origin.
+ */
+ struct pending_exception *primary_pe;
+
+ /*
+ * Number of pending_exceptions processing this chunk.
+ * When this drops to zero we must complete the origin bios.
+ * If incrementing or decrementing this, hold pe->snap->lock for
+ * the sibling concerned and not pe->primary_pe->snap->lock unless
+ * they are the same.
+ */
+ atomic_t sibling_count;
/* Pointer back to snapshot context */
struct dm_snapshot *snap;
return (n + size) & ~size;
}
+static void read_snapshot_metadata(struct dm_snapshot *s)
+{
+ if (s->store.read_metadata(&s->store)) {
+ down_write(&s->lock);
+ s->valid = 0;
+ up_write(&s->lock);
+
+ dm_table_event(s->table);
+ }
+}
+
/*
* Construct a snapshot mapping: <origin_dev> <COW-dev> <p/n> <chunk-size>
*/
s->chunk_shift = ffs(chunk_size) - 1;
s->valid = 1;
- s->have_metadata = 0;
+ s->active = 0;
s->last_percent = 0;
init_rwsem(&s->lock);
s->table = ti->table;
goto bad5;
}
+ /* Metadata must only be loaded into one table at once */
+ read_snapshot_metadata(s);
+
/* Add snapshot to the list of snapshots for this origin */
+ /* Exceptions aren't triggered till snapshot_resume() is called */
if (register_snapshot(s)) {
r = -EINVAL;
ti->error = "Cannot register snapshot origin";
{
struct dm_snapshot *s = (struct dm_snapshot *) ti->private;
+ /* Prevent further origin writes from using this snapshot. */
+ /* After this returns there can be no new kcopyd jobs. */
unregister_snapshot(s);
+ kcopyd_client_destroy(s->kcopyd_client);
+
exit_exception_table(&s->pending, pending_cache);
exit_exception_table(&s->complete, exception_cache);
dm_put_device(ti, s->origin);
dm_put_device(ti, s->cow);
- kcopyd_client_destroy(s->kcopyd_client);
+
kfree(s);
}
}
}
+static inline void error_snapshot_bios(struct pending_exception *pe)
+{
+ error_bios(bio_list_get(&pe->snapshot_bios));
+}
+
static struct bio *__flush_bios(struct pending_exception *pe)
{
- struct pending_exception *sibling;
+ /*
+ * If this pe is involved in a write to the origin and
+ * it is the last sibling to complete then release
+ * the bios for the original write to the origin.
+ */
+
+ if (pe->primary_pe &&
+ atomic_dec_and_test(&pe->primary_pe->sibling_count))
+ return bio_list_get(&pe->primary_pe->origin_bios);
- if (list_empty(&pe->siblings))
- return bio_list_get(&pe->origin_bios);
+ return NULL;
+}
- sibling = list_entry(pe->siblings.next,
- struct pending_exception, siblings);
+static void __invalidate_snapshot(struct dm_snapshot *s,
+ struct pending_exception *pe, int err)
+{
+ if (!s->valid)
+ return;
- list_del(&pe->siblings);
+ if (err == -EIO)
+ DMERR("Invalidating snapshot: Error reading/writing.");
+ else if (err == -ENOMEM)
+ DMERR("Invalidating snapshot: Unable to allocate exception.");
- /* This is fine as long as kcopyd is single-threaded. If kcopyd
- * becomes multi-threaded, we'll need some locking here.
- */
- bio_list_merge(&sibling->origin_bios, &pe->origin_bios);
+ if (pe)
+ remove_exception(&pe->e);
- return NULL;
+ if (s->store.drop_snapshot)
+ s->store.drop_snapshot(&s->store);
+
+ s->valid = 0;
+
+ dm_table_event(s->table);
}
static void pending_complete(struct pending_exception *pe, int success)
{
struct exception *e;
+ struct pending_exception *primary_pe;
struct dm_snapshot *s = pe->snap;
struct bio *flush = NULL;
- if (success) {
- e = alloc_exception();
- if (!e) {
- DMWARN("Unable to allocate exception.");
- down_write(&s->lock);
- s->store.drop_snapshot(&s->store);
- s->valid = 0;
- flush = __flush_bios(pe);
- up_write(&s->lock);
-
- error_bios(bio_list_get(&pe->snapshot_bios));
- goto out;
- }
- *e = pe->e;
-
- /*
- * Add a proper exception, and remove the
- * in-flight exception from the list.
- */
+ if (!success) {
+ /* Read/write error - snapshot is unusable */
down_write(&s->lock);
- insert_exception(&s->complete, e);
- remove_exception(&pe->e);
+ __invalidate_snapshot(s, pe, -EIO);
flush = __flush_bios(pe);
-
- /* Submit any pending write bios */
up_write(&s->lock);
- flush_bios(bio_list_get(&pe->snapshot_bios));
- } else {
- /* Read/write error - snapshot is unusable */
+ error_snapshot_bios(pe);
+ goto out;
+ }
+
+ e = alloc_exception();
+ if (!e) {
down_write(&s->lock);
- if (s->valid)
- DMERR("Error reading/writing snapshot");
- s->store.drop_snapshot(&s->store);
- s->valid = 0;
- remove_exception(&pe->e);
+ __invalidate_snapshot(s, pe, -ENOMEM);
flush = __flush_bios(pe);
up_write(&s->lock);
- error_bios(bio_list_get(&pe->snapshot_bios));
+ error_snapshot_bios(pe);
+ goto out;
+ }
+ *e = pe->e;
- dm_table_event(s->table);
+ /*
+ * Add a proper exception, and remove the
+ * in-flight exception from the list.
+ */
+ down_write(&s->lock);
+ if (!s->valid) {
+ flush = __flush_bios(pe);
+ up_write(&s->lock);
+
+ free_exception(e);
+
+ error_snapshot_bios(pe);
+ goto out;
}
+ insert_exception(&s->complete, e);
+ remove_exception(&pe->e);
+ flush = __flush_bios(pe);
+
+ up_write(&s->lock);
+
+ /* Submit any pending write bios */
+ flush_bios(bio_list_get(&pe->snapshot_bios));
+
out:
- free_pending_exception(pe);
+ primary_pe = pe->primary_pe;
+
+ /*
+ * Free the pe if it's not linked to an origin write or if
+ * it's not itself a primary pe.
+ */
+ 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->sibling_count))
+ free_pending_exception(primary_pe);
if (flush)
flush_bios(flush);
/*
* Dispatches the copy operation to kcopyd.
*/
-static inline void start_copy(struct pending_exception *pe)
+static void start_copy(struct pending_exception *pe)
{
struct dm_snapshot *s = pe->snap;
struct io_region src, dest;
if (e) {
/* cast the exception to a pending exception */
pe = container_of(e, struct pending_exception, e);
+ goto out;
+ }
- } else {
- /*
- * Create a new pending exception, we don't want
- * to hold the lock while we do this.
- */
- up_write(&s->lock);
- pe = alloc_pending_exception();
- down_write(&s->lock);
+ /*
+ * Create a new pending exception, we don't want
+ * to hold the lock while we do this.
+ */
+ up_write(&s->lock);
+ pe = alloc_pending_exception();
+ down_write(&s->lock);
- e = lookup_exception(&s->pending, chunk);
- if (e) {
- free_pending_exception(pe);
- pe = container_of(e, struct pending_exception, e);
- } else {
- pe->e.old_chunk = chunk;
- bio_list_init(&pe->origin_bios);
- bio_list_init(&pe->snapshot_bios);
- INIT_LIST_HEAD(&pe->siblings);
- pe->snap = s;
- pe->started = 0;
-
- if (s->store.prepare_exception(&s->store, &pe->e)) {
- free_pending_exception(pe);
- s->valid = 0;
- return NULL;
- }
+ if (!s->valid) {
+ free_pending_exception(pe);
+ return NULL;
+ }
- insert_exception(&s->pending, &pe->e);
- }
+ e = lookup_exception(&s->pending, chunk);
+ if (e) {
+ free_pending_exception(pe);
+ pe = container_of(e, struct pending_exception, e);
+ goto out;
+ }
+
+ pe->e.old_chunk = chunk;
+ bio_list_init(&pe->origin_bios);
+ bio_list_init(&pe->snapshot_bios);
+ pe->primary_pe = NULL;
+ atomic_set(&pe->sibling_count, 1);
+ pe->snap = s;
+ pe->started = 0;
+
+ if (s->store.prepare_exception(&s->store, &pe->e)) {
+ free_pending_exception(pe);
+ return NULL;
}
+ insert_exception(&s->pending, &pe->e);
+
+ out:
return pe;
}
{
struct exception *e;
struct dm_snapshot *s = (struct dm_snapshot *) ti->private;
+ int copy_needed = 0;
int r = 1;
chunk_t chunk;
- struct pending_exception *pe;
+ struct pending_exception *pe = NULL;
chunk = sector_to_chunk(s, bio->bi_sector);
/* Full snapshots are not usable */
+ /* To get here the table must be live so s->active is always set. */
if (!s->valid)
- return -1;
+ return -EIO;
+
+ if (unlikely(bio_barrier(bio)))
+ return -EOPNOTSUPP;
/*
* Write to snapshot - higher level takes care of RW/RO
* to copy an exception */
down_write(&s->lock);
+ if (!s->valid) {
+ r = -EIO;
+ goto out_unlock;
+ }
+
/* If the block is already remapped - use that, else remap it */
e = lookup_exception(&s->complete, chunk);
if (e) {
remap_exception(s, e, bio);
- up_write(&s->lock);
-
- } else {
- pe = __find_pending_exception(s, bio);
-
- if (!pe) {
- if (s->store.drop_snapshot)
- s->store.drop_snapshot(&s->store);
- s->valid = 0;
- r = -EIO;
- up_write(&s->lock);
- } else {
- remap_exception(s, &pe->e, bio);
- bio_list_add(&pe->snapshot_bios, bio);
-
- if (!pe->started) {
- /* this is protected by snap->lock */
- pe->started = 1;
- up_write(&s->lock);
- start_copy(pe);
- } else
- up_write(&s->lock);
- r = 0;
- }
+ goto out_unlock;
+ }
+
+ pe = __find_pending_exception(s, bio);
+ if (!pe) {
+ __invalidate_snapshot(s, pe, -ENOMEM);
+ r = -EIO;
+ goto out_unlock;
+ }
+
+ remap_exception(s, &pe->e, bio);
+ bio_list_add(&pe->snapshot_bios, bio);
+
+ if (!pe->started) {
+ /* this is protected by snap->lock */
+ pe->started = 1;
+ copy_needed = 1;
}
+ r = 0;
+
+ out_unlock:
+ up_write(&s->lock);
+
+ if (copy_needed)
+ start_copy(pe);
} else {
/*
* FIXME: this read path scares me because we
/* Do reads */
down_read(&s->lock);
+ if (!s->valid) {
+ up_read(&s->lock);
+ return -EIO;
+ }
+
/* See if it it has been remapped */
e = lookup_exception(&s->complete, chunk);
if (e)
{
struct dm_snapshot *s = (struct dm_snapshot *) ti->private;
- if (s->have_metadata)
- return;
-
- if (s->store.read_metadata(&s->store)) {
- down_write(&s->lock);
- s->valid = 0;
- up_write(&s->lock);
- }
-
- s->have_metadata = 1;
+ down_write(&s->lock);
+ s->active = 1;
+ up_write(&s->lock);
}
static int snapshot_status(struct dm_target *ti, status_type_t type,
snap->store.fraction_full(&snap->store,
&numerator,
&denominator);
- snprintf(result, maxlen,
- SECTOR_FORMAT "/" SECTOR_FORMAT,
- numerator, denominator);
+ snprintf(result, maxlen, "%llu/%llu",
+ (unsigned long long)numerator,
+ (unsigned long long)denominator);
}
else
snprintf(result, maxlen, "Unknown");
* to make private copies if the output is to
* make sense.
*/
- snprintf(result, maxlen, "%s %s %c " SECTOR_FORMAT,
+ snprintf(result, maxlen, "%s %s %c %llu",
snap->origin->name, snap->cow->name,
- snap->type, snap->chunk_size);
+ snap->type,
+ (unsigned long long)snap->chunk_size);
break;
}
/*-----------------------------------------------------------------
* Origin methods
*---------------------------------------------------------------*/
-static void list_merge(struct list_head *l1, struct list_head *l2)
-{
- struct list_head *l1_n, *l2_p;
-
- l1_n = l1->next;
- l2_p = l2->prev;
-
- l1->next = l2;
- l2->prev = l1;
-
- l2_p->next = l1_n;
- l1_n->prev = l2_p;
-}
-
static int __origin_write(struct list_head *snapshots, struct bio *bio)
{
- int r = 1, first = 1;
+ int r = 1, first = 0;
struct dm_snapshot *snap;
struct exception *e;
- struct pending_exception *pe, *last = NULL;
+ struct pending_exception *pe, *next_pe, *primary_pe = NULL;
chunk_t chunk;
+ LIST_HEAD(pe_queue);
/* Do all the snapshots on this origin */
list_for_each_entry (snap, snapshots, list) {
- /* Only deal with valid snapshots */
- if (!snap->valid)
- continue;
-
down_write(&snap->lock);
+ /* Only deal with valid and active snapshots */
+ if (!snap->valid || !snap->active)
+ goto next_snapshot;
+
+ /* Nothing to do if writing beyond end of snapshot */
+ if (bio->bi_sector >= dm_table_get_size(snap->table))
+ goto next_snapshot;
+
/*
* Remember, different snapshots can have
* different chunk sizes.
* Check exception table to see if block
* is already remapped in this snapshot
* and trigger an exception if not.
+ *
+ * sibling_count is initialised to 1 so pending_complete()
+ * won't destroy the primary_pe while we're inside this loop.
*/
e = lookup_exception(&snap->complete, chunk);
- if (!e) {
- pe = __find_pending_exception(snap, bio);
- if (!pe) {
- snap->store.drop_snapshot(&snap->store);
- snap->valid = 0;
-
- } else {
- if (last)
- list_merge(&pe->siblings,
- &last->siblings);
-
- last = pe;
- r = 0;
+ if (e)
+ goto next_snapshot;
+
+ pe = __find_pending_exception(snap, bio);
+ if (!pe) {
+ __invalidate_snapshot(snap, pe, ENOMEM);
+ goto next_snapshot;
+ }
+
+ if (!primary_pe) {
+ /*
+ * Either every pe here has same
+ * primary_pe or none has one yet.
+ */
+ if (pe->primary_pe)
+ primary_pe = pe->primary_pe;
+ else {
+ primary_pe = pe;
+ first = 1;
}
+
+ bio_list_add(&primary_pe->origin_bios, bio);
+
+ r = 0;
}
+ if (!pe->primary_pe) {
+ atomic_inc(&primary_pe->sibling_count);
+ pe->primary_pe = primary_pe;
+ }
+
+ if (!pe->started) {
+ pe->started = 1;
+ list_add_tail(&pe->list, &pe_queue);
+ }
+
+ next_snapshot:
up_write(&snap->lock);
}
+ if (!primary_pe)
+ goto out;
+
/*
- * Now that we have a complete pe list we can start the copying.
+ * If this is the first time we're processing this chunk and
+ * sibling_count is now 1 it means all the pending exceptions
+ * got completed while we were in the loop above, so it falls to
+ * us here to remove the primary_pe and submit any origin_bios.
*/
- if (last) {
- pe = last;
- do {
- down_write(&pe->snap->lock);
- if (first)
- bio_list_add(&pe->origin_bios, bio);
- if (!pe->started) {
- pe->started = 1;
- up_write(&pe->snap->lock);
- start_copy(pe);
- } else
- up_write(&pe->snap->lock);
- first = 0;
- pe = list_entry(pe->siblings.next,
- struct pending_exception, siblings);
-
- } while (pe != last);
+
+ if (first && atomic_dec_and_test(&primary_pe->sibling_count)) {
+ flush_bios(bio_list_get(&primary_pe->origin_bios));
+ free_pending_exception(primary_pe);
+ /* If we got here, pe_queue is necessarily empty. */
+ goto out;
}
+ /*
+ * Now that we have a complete pe list we can start the copying.
+ */
+ list_for_each_entry_safe(pe, next_pe, &pe_queue, list)
+ start_copy(pe);
+
+ out:
return r;
}
struct dm_dev *dev = (struct dm_dev *) ti->private;
bio->bi_bdev = dev->bdev;
+ if (unlikely(bio_barrier(bio)))
+ return -EOPNOTSUPP;
+
/* Only tell snapshots if this is a write */
return (bio_rw(bio) == WRITE) ? do_origin(dev, bio) : 1;
}
static struct target_type origin_target = {
.name = "snapshot-origin",
- .version = {1, 0, 1},
+ .version = {1, 1, 0},
.module = THIS_MODULE,
.ctr = origin_ctr,
.dtr = origin_dtr,
static struct target_type snapshot_target = {
.name = "snapshot",
- .version = {1, 0, 1},
+ .version = {1, 1, 0},
.module = THIS_MODULE,
.ctr = snapshot_ctr,
.dtr = snapshot_dtr,
goto bad4;
}
- pending_pool = mempool_create(128, mempool_alloc_slab,
- mempool_free_slab, pending_cache);
+ pending_pool = mempool_create_slab_pool(128, pending_cache);
if (!pending_pool) {
DMERR("Couldn't create pending pool.");
r = -ENOMEM;
git://git.onelab.eu / linux-2.6.git / blobdiff