diff options
| -rw-r--r-- | drivers/md/dm-snap.c | 155 |
1 files changed, 49 insertions, 106 deletions
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c index 446827f9823..c01e0dafec3 100644 --- a/drivers/md/dm-snap.c +++ b/drivers/md/dm-snap.c @@ -142,28 +142,6 @@ struct dm_snap_pending_exception { struct bio_list origin_bios; struct bio_list snapshot_bios; - /* - * Short-term queue of pending exceptions prior to submission. - */ - struct list_head list; - - /* - * The primary pending_exception is the one that holds - * the ref_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 dm_snap_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 ref_count; - /* Pointer back to snapshot context */ struct dm_snapshot *snap; @@ -1019,6 +997,26 @@ static void flush_queued_bios(struct work_struct *work) flush_bios(queued_bios); } +static int do_origin(struct dm_dev *origin, struct bio *bio); + +/* + * Flush a list of buffers. + */ +static void retry_origin_bios(struct dm_snapshot *s, struct bio *bio) +{ + struct bio *n; + int r; + + while (bio) { + n = bio->bi_next; + bio->bi_next = NULL; + r = do_origin(s->origin, bio); + if (r == DM_MAPIO_REMAPPED) + generic_make_request(bio); + bio = n; + } +} + /* * Error a list of buffers. */ @@ -1052,39 +1050,6 @@ static void __invalidate_snapshot(struct dm_snapshot *s, int err) dm_table_event(s->ti->table); } -static void get_pending_exception(struct dm_snap_pending_exception *pe) -{ - atomic_inc(&pe->ref_count); -} - -static struct bio *put_pending_exception(struct dm_snap_pending_exception *pe) -{ - struct dm_snap_pending_exception *primary_pe; - struct bio *origin_bios = NULL; - - primary_pe = pe->primary_pe; - - /* - * 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 (primary_pe && - 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 - * it's not itself a primary pe. - */ - if (!primary_pe || primary_pe != pe) - free_pending_exception(pe); - - return origin_bios; -} - static void pending_complete(struct dm_snap_pending_exception *pe, int success) { struct dm_exception *e; @@ -1129,7 +1094,8 @@ static void pending_complete(struct dm_snap_pending_exception *pe, int success) out: dm_remove_exception(&pe->e); snapshot_bios = bio_list_get(&pe->snapshot_bios); - origin_bios = put_pending_exception(pe); + origin_bios = bio_list_get(&pe->origin_bios); + free_pending_exception(pe); up_write(&s->lock); @@ -1139,7 +1105,7 @@ static void pending_complete(struct dm_snap_pending_exception *pe, int success) else flush_bios(snapshot_bios); - flush_bios(origin_bios); + retry_origin_bios(s, origin_bios); } static void commit_callback(void *context, int success) @@ -1226,8 +1192,6 @@ __find_pending_exception(struct dm_snapshot *s, pe->e.old_chunk = chunk; bio_list_init(&pe->origin_bios); bio_list_init(&pe->snapshot_bios); - pe->primary_pe = NULL; - atomic_set(&pe->ref_count, 0); pe->started = 0; if (s->store->type->prepare_exception(s->store, &pe->e)) { @@ -1235,7 +1199,6 @@ __find_pending_exception(struct dm_snapshot *s, return NULL; } - get_pending_exception(pe); dm_insert_exception(&s->pending, &pe->e); return pe; @@ -1492,16 +1455,16 @@ static int snapshot_iterate_devices(struct dm_target *ti, static int __origin_write(struct list_head *snapshots, sector_t sector, struct bio *bio) { - int r = DM_MAPIO_REMAPPED, first = 0; + int r = DM_MAPIO_REMAPPED; struct dm_snapshot *snap; struct dm_exception *e; - struct dm_snap_pending_exception *pe, *next_pe, *primary_pe = NULL; + struct dm_snap_pending_exception *pe; + struct dm_snap_pending_exception *pe_to_start_now = NULL; + struct dm_snap_pending_exception *pe_to_start_last = NULL; chunk_t chunk; - LIST_HEAD(pe_queue); /* Do all the snapshots on this origin */ list_for_each_entry (snap, snapshots, list) { - down_write(&snap->lock); /* Only deal with valid and active snapshots */ @@ -1522,9 +1485,6 @@ static int __origin_write(struct list_head *snapshots, sector_t sector, * Check exception table to see if block * is already remapped in this snapshot * and trigger an exception if not. - * - * ref_count is initialised to 1 so pending_complete() - * won't destroy the primary_pe while we're inside this loop. */ e = dm_lookup_exception(&snap->complete, chunk); if (e) @@ -1554,60 +1514,43 @@ static int __origin_write(struct list_head *snapshots, sector_t sector, } } - 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; - } - - if (bio) - bio_list_add(&primary_pe->origin_bios, bio); + r = DM_MAPIO_SUBMITTED; - r = DM_MAPIO_SUBMITTED; - } + /* + * If an origin bio was supplied, queue it to wait for the + * completion of this exception, and start this one last, + * at the end of the function. + */ + if (bio) { + bio_list_add(&pe->origin_bios, bio); + bio = NULL; - if (!pe->primary_pe) { - pe->primary_pe = primary_pe; - get_pending_exception(primary_pe); + if (!pe->started) { + pe->started = 1; + pe_to_start_last = pe; + } } if (!pe->started) { pe->started = 1; - list_add_tail(&pe->list, &pe_queue); + pe_to_start_now = pe; } next_snapshot: up_write(&snap->lock); - } - if (!primary_pe) - return r; - - /* - * If this is the first time we're processing this chunk and - * ref_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 (first && atomic_dec_and_test(&primary_pe->ref_count)) { - flush_bios(bio_list_get(&primary_pe->origin_bios)); - free_pending_exception(primary_pe); - /* If we got here, pe_queue is necessarily empty. */ - return r; + if (pe_to_start_now) { + start_copy(pe_to_start_now); + pe_to_start_now = NULL; + } } /* - * Now that we have a complete pe list we can start the copying. + * Submit the exception against which the bio is queued last, + * to give the other exceptions a head start. */ - list_for_each_entry_safe(pe, next_pe, &pe_queue, list) - start_copy(pe); + if (pe_to_start_last) + start_copy(pe_to_start_last); return r; } |