From e88a36ec961b8c1899c59c5e4ae35a318c0209d3 Mon Sep 17 00:00:00 2001 From: Josh Durgin Date: Mon, 21 Nov 2011 18:14:25 -0800 Subject: [PATCH] rbd: return errors for mapped but deleted snapshot When a snapshot is deleted, the OSD will return ENOENT when reading from it. This is normally interpreted as a hole by rbd, which will return zeroes. To minimize the time in which this can happen, stop requests early when we are notified that our snapshot no longer exists. [elder@inktank.com: updated __rbd_init_snaps_header() logic] Signed-off-by: Josh Durgin Reviewed-by: Alex Elder --- drivers/block/rbd.c | 32 ++++++++++++++++++++++++++++++-- 1 file changed, 30 insertions(+), 2 deletions(-) diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c index b124442..730d0ce 100644 --- a/drivers/block/rbd.c +++ b/drivers/block/rbd.c @@ -172,9 +172,13 @@ struct rbd_device { /* protects updating the header */ struct rw_semaphore header_rwsem; + /* name of the snapshot this device reads from */ char *snap_name; + /* id of the snapshot this device reads from */ u64 snap_id; /* current snapshot id */ - int read_only; + /* whether the snap_id this device reads from still exists */ + bool snap_exists; + int read_only; struct list_head node; @@ -597,6 +601,7 @@ static int rbd_header_set_snap(struct rbd_device *rbd_dev, u64 *size) else snapc->seq = 0; rbd_dev->snap_id = CEPH_NOSNAP; + rbd_dev->snap_exists = false; rbd_dev->read_only = 0; if (size) *size = header->image_size; @@ -606,6 +611,7 @@ static int rbd_header_set_snap(struct rbd_device *rbd_dev, u64 *size) if (ret < 0) goto done; rbd_dev->snap_id = snapc->seq; + rbd_dev->snap_exists = true; rbd_dev->read_only = 1; } @@ -1468,6 +1474,21 @@ static void rbd_rq_fn(struct request_queue *q) spin_unlock_irq(q->queue_lock); + if (rbd_dev->snap_id != CEPH_NOSNAP) { + bool snap_exists; + + down_read(&rbd_dev->header_rwsem); + snap_exists = rbd_dev->snap_exists; + up_read(&rbd_dev->header_rwsem); + + if (!snap_exists) { + dout("request for non-existent snapshot"); + spin_lock_irq(q->queue_lock); + __blk_end_request_all(rq, -ENXIO); + continue; + } + } + dout("%s 0x%x bytes at 0x%llx\n", do_write ? "write" : "read", size, blk_rq_pos(rq) * SECTOR_SIZE); @@ -2088,7 +2109,14 @@ static int __rbd_init_snaps_header(struct rbd_device *rbd_dev) cur_id = rbd_dev->header.snapc->snaps[i - 1]; if (!i || old_snap->id < cur_id) { - /* old_snap->id was skipped, thus was removed */ + /* + * old_snap->id was skipped, thus was + * removed. If this rbd_dev is mapped to + * the removed snapshot, record that it no + * longer exists, to prevent further I/O. + */ + if (rbd_dev->snap_id == old_snap->id) + rbd_dev->snap_exists = false; __rbd_remove_snap_dev(rbd_dev, old_snap); continue; } -- 2.7.4