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@xxxxxxxxxxx: updated __rbd_init_snaps_header() logic]
Signed-off-by: Josh Durgin <josh.durgin@xxxxxxxxxxx>
Reviewed-by: Alex Elder <elder@xxxxxxxxxxx>
---
drivers/block/rbd.c | 32 ++++++++++++++++++++++++++++++--
1 files 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;
}
--
1.7.5.4
--
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