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68c9417b19
Now open_mutex is used to synchronize partition operations (e.g,
blk_drop_partitions() and blkdev_reread_part()), however it makes
nbd driver broken, because nbd may call del_gendisk() in nbd_release()
or nbd_genl_disconnect() if NBD_CFLAG_DESTROY_ON_DISCONNECT is enabled,
and deadlock occurs, as shown below:
// AB-BA dead-lock
nbd_genl_disconnect blkdev_open
nbd_disconnect_and_put
lock bd_mutex
// last ref
nbd_put
lock nbd_index_mutex
del_gendisk
nbd_open
try lock nbd_index_mutex
try lock bd_mutex
or
// AA dead-lock
nbd_release
lock bd_mutex
nbd_put
try lock bd_mutex
Instead of fixing block layer (e.g, introduce another lock), fixing
the nbd driver to call del_gendisk() in a kworker when
NBD_DESTROY_ON_DISCONNECT is enabled. When NBD_DESTROY_ON_DISCONNECT
is disabled, nbd device will always be destroy through module removal,
and there is no risky of deadlock.
To ensure the reuse of nbd index succeeds, moving the calling of
idr_remove() after del_gendisk(), so if the reused index is not found
in nbd_index_idr, the old disk must have been deleted. And reusing
the existing destroy_complete mechanism to ensure nbd_genl_connect()
will wait for the completion of del_gendisk().
Also adding a new workqueue for nbd removal, so nbd_cleanup()
can ensure all removals complete before exits.
Reported-by: syzbot+0fe7752e52337864d29b@syzkaller.appspotmail.com
Fixes:
|
||
|---|---|---|
| .. | ||
| aoe | ||
| drbd | ||
| mtip32xx | ||
| null_blk | ||
| paride | ||
| rnbd | ||
| rsxx | ||
| xen-blkback | ||
| zram | ||
| amiflop.c | ||
| ataflop.c | ||
| brd.c | ||
| cryptoloop.c | ||
| floppy.c | ||
| Kconfig | ||
| loop.c | ||
| loop.h | ||
| Makefile | ||
| n64cart.c | ||
| nbd.c | ||
| pktcdvd.c | ||
| ps3disk.c | ||
| ps3vram.c | ||
| rbd.c | ||
| rbd_types.h | ||
| sunvdc.c | ||
| swim.c | ||
| swim3.c | ||
| swim_asm.S | ||
| sx8.c | ||
| virtio_blk.c | ||
| xen-blkfront.c | ||
| z2ram.c | ||