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rbd: remove snapshot existence validation code

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RBD_DEV_FLAG_EXISTS check in rbd_queue_workfn() is racy and leads to
inconsistent behaviour.  If the object (or its snapshot) isn't there,
the OSD returns ENOENT.  A read submitted before the snapshot removal
notification is processed would be zero-filled and ended with status
OK, while future reads would be failed with IOERR.  It also doesn't
handle a case when an image that is mapped read-only is removed.

On top of this, because watch is no longer established for read-only
mappings, we no longer get notifications, so rbd_exists_validate() is
effectively dead code.  While failing requests rather than returning
zeros is a good thing, RBD_DEV_FLAG_EXISTS is not it.

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Jason Dillaman <dillaman@redhat.com>
Reviewed-by: Dongsheng Yang <dongsheng.yang@easystack.cn>
This commit is contained in:
Ilya Dryomov 2019-11-18 12:51:02 +01:00
parent b9ef2b8858
commit 686238b743
1 changed files with 3 additions and 39 deletions
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42
drivers/block/rbd.c
View file

@ -462,7 +462,7 @@ struct rbd_device {
* by rbd_dev->lock
*/
enum rbd_dev_flags {
RBD_DEV_FLAG_EXISTS, /* mapped snapshot has not been deleted */
RBD_DEV_FLAG_EXISTS, /* rbd_dev_device_setup() ran */
RBD_DEV_FLAG_REMOVING, /* this mapping is being removed */
RBD_DEV_FLAG_READONLY, /* -o ro or snapshot */
};
@ -4865,19 +4865,6 @@ static void rbd_queue_workfn(struct work_struct *work)
rbd_assert(!rbd_is_snap(rbd_dev));
}
/*
* Quit early if the mapped snapshot no longer exists. It's
* still possible the snapshot will have disappeared by the
* time our request arrives at the osd, but there's no sense in
* sending it if we already know.
*/
if (!test_bit(RBD_DEV_FLAG_EXISTS, &rbd_dev->flags)) {
dout("request for non-existent snapshot");
rbd_assert(rbd_is_snap(rbd_dev));
result = -ENXIO;
goto err_rq;
}
if (offset && length > U64_MAX - offset + 1) {
rbd_warn(rbd_dev, "bad request range (%llu~%llu)", offset,
length);
@ -5057,25 +5044,6 @@ static int rbd_dev_v1_header_info(struct rbd_device *rbd_dev)
return ret;
}
/*
* Clear the rbd device's EXISTS flag if the snapshot it's mapped to
* has disappeared from the (just updated) snapshot context.
*/
static void rbd_exists_validate(struct rbd_device *rbd_dev)
{
u64 snap_id;
if (!test_bit(RBD_DEV_FLAG_EXISTS, &rbd_dev->flags))
return;
snap_id = rbd_dev->spec->snap_id;
if (snap_id == CEPH_NOSNAP)
return;
if (rbd_dev_snap_index(rbd_dev, snap_id) == BAD_SNAP_INDEX)
clear_bit(RBD_DEV_FLAG_EXISTS, &rbd_dev->flags);
}
static void rbd_dev_update_size(struct rbd_device *rbd_dev)
{
sector_t size;
@ -5116,12 +5084,8 @@ static int rbd_dev_refresh(struct rbd_device *rbd_dev)
goto out;
}
if (!rbd_is_snap(rbd_dev)) {
rbd_dev->mapping.size = rbd_dev->header.image_size;
} else {
/* validate mapped snapshot's EXISTS flag */
rbd_exists_validate(rbd_dev);
}
rbd_assert(!rbd_is_snap(rbd_dev));
rbd_dev->mapping.size = rbd_dev->header.image_size;
out:
up_write(&rbd_dev->header_rwsem);