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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 <josh.durgin@inktank.com>
Reviewed-by: Alex Elder <elder@inktank.com>
This commit is contained in:
Josh Durgin 2011-11-21 18:14:25 -08:00 committed by Sage Weil
parent 048a9d2d06
commit e88a36ec96
1 changed files with 30 additions and 2 deletions
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32
drivers/block/rbd.c
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@ -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;
}