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rbd: avoid a deadlock on header_rwsem when flushing notifies
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>
This commit is contained in:
parent
8f3d9f3542
commit
0e4e1de5b6
1 changed files with 13 additions and 4 deletions
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@ -4527,6 +4527,10 @@ 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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}
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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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{
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cancel_tasks_sync(rbd_dev);
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@ -6907,6 +6911,9 @@ 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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* 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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*
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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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static int rbd_dev_image_probe(struct rbd_device *rbd_dev, int depth)
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{
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@ -6936,6 +6943,9 @@ 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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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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if (ret) {
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if (ret == -ENOENT && !need_watch)
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@ -6987,6 +6997,8 @@ static int rbd_dev_image_probe(struct rbd_device *rbd_dev, int depth)
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err_out_probe:
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rbd_dev_unprobe(rbd_dev);
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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 (need_watch)
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rbd_unregister_watch(rbd_dev);
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err_out_format:
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@ -7050,12 +7062,9 @@ static ssize_t do_rbd_add(struct bus_type *bus,
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goto err_out_rbd_dev;
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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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if (rc < 0) {
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up_write(&rbd_dev->header_rwsem);
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if (rc < 0)
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goto err_out_rbd_dev;
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}
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if (rbd_dev->opts->alloc_size > rbd_dev->layout.object_size) {
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rbd_warn(rbd_dev, "alloc_size adjusted to %u",
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