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| author | Ilya Dryomov <idryomov@gmail.com> | 2020-03-13 11:20:51 +0100 |
|---|---|---|
| committer | Ilya Dryomov <idryomov@gmail.com> | 2020-04-13 08:55:49 +0200 |
| commit | 0e4e1de5b63fa423b13593337a27fd2d2b0bcf77 (patch) | |
| tree | 8abbb9cb2d0db92749231abb3214c5b2699dd11c /drivers/block/rbd.c | |
| parent | Linux 5.7-rc1 (diff) | |
| download | linux-0e4e1de5b63fa423b13593337a27fd2d2b0bcf77.tar.xz linux-0e4e1de5b63fa423b13593337a27fd2d2b0bcf77.zip | |
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: 811c66887746 ("rbd: fix rbd map vs notify races")
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Jason Dillaman <dillaman@redhat.com>
Diffstat (limited to 'drivers/block/rbd.c')
| -rw-r--r-- | drivers/block/rbd.c | 17 |
1 files changed, 13 insertions, 4 deletions
diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c index 1e0a6b19ae0d..ff2377e6d12c 100644 --- a/drivers/block/rbd.c +++ b/drivers/block/rbd.c @@ -4527,6 +4527,10 @@ static void cancel_tasks_sync(struct rbd_device *rbd_dev) cancel_work_sync(&rbd_dev->unlock_work); } +/* + * header_rwsem must not be held to avoid a deadlock with + * rbd_dev_refresh() when flushing notifies. + */ static void rbd_unregister_watch(struct rbd_device *rbd_dev) { cancel_tasks_sync(rbd_dev); @@ -6907,6 +6911,9 @@ static void rbd_dev_image_release(struct rbd_device *rbd_dev) * device. If this image is the one being mapped (i.e., not a * parent), initiate a watch on its header object before using that * object to get detailed information about the rbd image. + * + * On success, returns with header_rwsem held for write if called + * with @depth == 0. */ static int rbd_dev_image_probe(struct rbd_device *rbd_dev, int depth) { @@ -6936,6 +6943,9 @@ static int rbd_dev_image_probe(struct rbd_device *rbd_dev, int depth) } } + if (!depth) + down_write(&rbd_dev->header_rwsem); + ret = rbd_dev_header_info(rbd_dev); if (ret) { if (ret == -ENOENT && !need_watch) @@ -6987,6 +6997,8 @@ static int rbd_dev_image_probe(struct rbd_device *rbd_dev, int depth) err_out_probe: rbd_dev_unprobe(rbd_dev); err_out_watch: + if (!depth) + up_write(&rbd_dev->header_rwsem); if (need_watch) rbd_unregister_watch(rbd_dev); err_out_format: @@ -7050,12 +7062,9 @@ static ssize_t do_rbd_add(struct bus_type *bus, goto err_out_rbd_dev; } - down_write(&rbd_dev->header_rwsem); rc = rbd_dev_image_probe(rbd_dev, 0); - if (rc < 0) { - up_write(&rbd_dev->header_rwsem); + if (rc < 0) goto err_out_rbd_dev; - } if (rbd_dev->opts->alloc_size > rbd_dev->layout.object_size) { rbd_warn(rbd_dev, "alloc_size adjusted to %u", |