rbd: avoid a deadlock on header_rwsem when flushing notifies
[ Upstream commit5.4-rM2-2.2.x-imx-squashed0e4e1de5b6
] rbd_unregister_watch() flushes notifies and therefore cannot be called under header_rwsem because a header update notify takes header_rwsem to synchronize with "rbd map". If mapping an image fails after the watch is established and a header update notify sneaks in, we deadlock when erroring out from rbd_dev_image_probe(). Move watch registration and unregistration out of the critical section. The only reason they were put there was to make header_rwsem management slightly more obvious. Fixes:811c668877
("rbd: fix rbd map vs notify races") Signed-off-by: Ilya Dryomov <idryomov@gmail.com> Reviewed-by: Jason Dillaman <dillaman@redhat.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
parent
a362482b23
commit
88a57e387c
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@ -4636,6 +4636,10 @@ static void cancel_tasks_sync(struct rbd_device *rbd_dev)
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cancel_work_sync(&rbd_dev->unlock_work);
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cancel_work_sync(&rbd_dev->unlock_work);
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}
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}
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/*
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* header_rwsem must not be held to avoid a deadlock with
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* rbd_dev_refresh() when flushing notifies.
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*/
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static void rbd_unregister_watch(struct rbd_device *rbd_dev)
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static void rbd_unregister_watch(struct rbd_device *rbd_dev)
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{
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{
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cancel_tasks_sync(rbd_dev);
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cancel_tasks_sync(rbd_dev);
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@ -6942,6 +6946,9 @@ static void rbd_dev_image_release(struct rbd_device *rbd_dev)
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* device. If this image is the one being mapped (i.e., not a
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* device. If this image is the one being mapped (i.e., not a
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* parent), initiate a watch on its header object before using that
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* parent), initiate a watch on its header object before using that
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* object to get detailed information about the rbd image.
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* object to get detailed information about the rbd image.
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*
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* On success, returns with header_rwsem held for write if called
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* with @depth == 0.
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*/
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*/
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static int rbd_dev_image_probe(struct rbd_device *rbd_dev, int depth)
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static int rbd_dev_image_probe(struct rbd_device *rbd_dev, int depth)
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{
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{
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@ -6974,6 +6981,9 @@ static int rbd_dev_image_probe(struct rbd_device *rbd_dev, int depth)
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}
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}
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}
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}
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if (!depth)
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down_write(&rbd_dev->header_rwsem);
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ret = rbd_dev_header_info(rbd_dev);
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ret = rbd_dev_header_info(rbd_dev);
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if (ret)
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if (ret)
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goto err_out_watch;
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goto err_out_watch;
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@ -7027,6 +7037,8 @@ static int rbd_dev_image_probe(struct rbd_device *rbd_dev, int depth)
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err_out_probe:
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err_out_probe:
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rbd_dev_unprobe(rbd_dev);
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rbd_dev_unprobe(rbd_dev);
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err_out_watch:
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err_out_watch:
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if (!depth)
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up_write(&rbd_dev->header_rwsem);
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if (!depth)
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if (!depth)
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rbd_unregister_watch(rbd_dev);
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rbd_unregister_watch(rbd_dev);
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err_out_format:
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err_out_format:
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@ -7085,12 +7097,9 @@ static ssize_t do_rbd_add(struct bus_type *bus,
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goto err_out_rbd_dev;
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goto err_out_rbd_dev;
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}
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}
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down_write(&rbd_dev->header_rwsem);
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rc = rbd_dev_image_probe(rbd_dev, 0);
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rc = rbd_dev_image_probe(rbd_dev, 0);
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if (rc < 0) {
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if (rc < 0)
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up_write(&rbd_dev->header_rwsem);
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goto err_out_rbd_dev;
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goto err_out_rbd_dev;
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}
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/* If we are mapping a snapshot it must be marked read-only */
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/* If we are mapping a snapshot it must be marked read-only */
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if (rbd_dev->spec->snap_id != CEPH_NOSNAP)
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if (rbd_dev->spec->snap_id != CEPH_NOSNAP)
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