From 686238b7431dcca870ff0bc8ae280cdc89ee41c7 Mon Sep 17 00:00:00 2001 From: Ilya Dryomov Date: Mon, 18 Nov 2019 12:51:02 +0100 Subject: [PATCH] rbd: remove snapshot existence validation code 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 Reviewed-by: Jason Dillaman Reviewed-by: Dongsheng Yang --- drivers/block/rbd.c | 42 +++--------------------------------------- 1 file changed, 3 insertions(+), 39 deletions(-) diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c index 2a22bc24c886..ee2b15e67e96 100644 --- a/drivers/block/rbd.c +++ b/drivers/block/rbd.c @@ -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 @@ out: 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);