diff options
| -rw-r--r-- | drivers/md/dm-snap.c | 102 |
1 files changed, 65 insertions, 37 deletions
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c index a168963b757d..051e4d076323 100644 --- a/drivers/md/dm-snap.c +++ b/drivers/md/dm-snap.c @@ -1501,16 +1501,24 @@ static void pending_complete(void *context, int success) goto out; } - /* Check for conflicting reads */ - __check_for_conflicting_io(s, pe->e.old_chunk); - /* - * Add a proper exception, and remove the - * in-flight exception from the list. + * Add a proper exception. After inserting the completed exception all + * subsequent snapshot reads to this chunk will be redirected to the + * COW device. This ensures that we do not starve. Moreover, as long + * as the pending exception exists, neither origin writes nor snapshot + * merging can overwrite the chunk in origin. */ dm_insert_exception(&s->complete, e); + /* Wait for conflicting reads to drain */ + if (__chunk_is_tracked(s, pe->e.old_chunk)) { + mutex_unlock(&s->lock); + __check_for_conflicting_io(s, pe->e.old_chunk); + mutex_lock(&s->lock); + } + out: + /* Remove the in-flight exception from the list */ dm_remove_exception(&pe->e); snapshot_bios = bio_list_get(&pe->snapshot_bios); origin_bios = bio_list_get(&pe->origin_bios); @@ -1660,25 +1668,15 @@ __lookup_pending_exception(struct dm_snapshot *s, chunk_t chunk) } /* - * Looks to see if this snapshot already has a pending exception - * for this chunk, otherwise it allocates a new one and inserts - * it into the pending table. + * Inserts a pending exception into the pending table. * * NOTE: a write lock must be held on snap->lock before calling * this. */ static struct dm_snap_pending_exception * -__find_pending_exception(struct dm_snapshot *s, - struct dm_snap_pending_exception *pe, chunk_t chunk) +__insert_pending_exception(struct dm_snapshot *s, + struct dm_snap_pending_exception *pe, chunk_t chunk) { - struct dm_snap_pending_exception *pe2; - - pe2 = __lookup_pending_exception(s, chunk); - if (pe2) { - free_pending_exception(pe); - return pe2; - } - pe->e.old_chunk = chunk; bio_list_init(&pe->origin_bios); bio_list_init(&pe->snapshot_bios); @@ -1697,6 +1695,29 @@ __find_pending_exception(struct dm_snapshot *s, return pe; } +/* + * Looks to see if this snapshot already has a pending exception + * for this chunk, otherwise it allocates a new one and inserts + * it into the pending table. + * + * NOTE: a write lock must be held on snap->lock before calling + * this. + */ +static struct dm_snap_pending_exception * +__find_pending_exception(struct dm_snapshot *s, + struct dm_snap_pending_exception *pe, chunk_t chunk) +{ + struct dm_snap_pending_exception *pe2; + + pe2 = __lookup_pending_exception(s, chunk); + if (pe2) { + free_pending_exception(pe); + return pe2; + } + + return __insert_pending_exception(s, pe, chunk); +} + static void remap_exception(struct dm_snapshot *s, struct dm_exception *e, struct bio *bio, chunk_t chunk) { @@ -2107,7 +2128,7 @@ static int __origin_write(struct list_head *snapshots, sector_t sector, int r = DM_MAPIO_REMAPPED; struct dm_snapshot *snap; struct dm_exception *e; - struct dm_snap_pending_exception *pe; + struct dm_snap_pending_exception *pe, *pe2; struct dm_snap_pending_exception *pe_to_start_now = NULL; struct dm_snap_pending_exception *pe_to_start_last = NULL; chunk_t chunk; @@ -2137,17 +2158,17 @@ static int __origin_write(struct list_head *snapshots, sector_t sector, */ chunk = sector_to_chunk(snap->store, sector); - /* - * Check exception table to see if block - * is already remapped in this snapshot - * and trigger an exception if not. - */ - e = dm_lookup_exception(&snap->complete, chunk); - if (e) - goto next_snapshot; - pe = __lookup_pending_exception(snap, chunk); if (!pe) { + /* + * Check exception table to see if block is already + * remapped in this snapshot and trigger an exception + * if not. + */ + e = dm_lookup_exception(&snap->complete, chunk); + if (e) + goto next_snapshot; + mutex_unlock(&snap->lock); pe = alloc_pending_exception(snap); mutex_lock(&snap->lock); @@ -2157,16 +2178,23 @@ static int __origin_write(struct list_head *snapshots, sector_t sector, goto next_snapshot; } - e = dm_lookup_exception(&snap->complete, chunk); - if (e) { + pe2 = __lookup_pending_exception(snap, chunk); + + if (!pe2) { + e = dm_lookup_exception(&snap->complete, chunk); + if (e) { + free_pending_exception(pe); + goto next_snapshot; + } + + pe = __insert_pending_exception(snap, pe, chunk); + if (!pe) { + __invalidate_snapshot(snap, -ENOMEM); + goto next_snapshot; + } + } else { free_pending_exception(pe); - goto next_snapshot; - } - - pe = __find_pending_exception(snap, pe, chunk); - if (!pe) { - __invalidate_snapshot(snap, -ENOMEM); - goto next_snapshot; + pe = pe2; } } |