[ 133/171] rbd: return errors for mapped but deleted snapshot

Greg Kroah-Hartman
2013-01-15T23:26:56Z

From: Josh Durgin <josh.durgin@inktank.com>

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>
(cherry picked from commit e88a36ec961b8c1899c59c5e4ae35a318c0209d3)
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Conflicts:

drivers/block/rbd.c
---
drivers/block/rbd.c | 32 ++++++++++++++++++++++++++++++--
1 file changed, 30 insertions(+), 2 deletions(-)

--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -174,9 +174,13 @@ struct rbd_device {

/* protects updating the header */
struct rw_semaphore header_rwsem;
+ /* name of the snapshot this device reads from */
char snap_name[RBD_MAX_SNAP_NAME_LEN];
+ /* 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;

@@ -590,6 +594,7 @@ static int rbd_header_set_snap(struct rb
else
snapc->seq = 0;
dev->snap_id = CEPH_NOSNAP;
+ dev->snap_exists = false;
dev->read_only = 0;
if (size)
*size = header->image_size;
@@ -598,6 +603,7 @@ static int rbd_header_set_snap(struct rb
if (ret < 0)
goto done;
dev->snap_id = snapc->seq;
+ dev->snap_exists = true;
dev->read_only = 1;
}

@@ -1466,6 +1472,21 @@ static void rbd_rq_fn(struct request_que

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);
@@ -2069,7 +2090,14 @@ static int __rbd_init_snaps_header(struc
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;
}