xemu/nbd
Vladimir Sementsov-Ogievskiy 453cc6be0a nbd: make nbd_export_close_all() synchronous
Consider nbd_export_close_all(). The call-stack looks like this:
 nbd_export_close_all() -> nbd_export_close -> call client_close() for
each client.

client_close() doesn't guarantee that client is closed: nbd_trip()
keeps reference to it. So, nbd_export_close_all() just reduce
reference counter on export and removes it from the list, but doesn't
guarantee that nbd_trip() finished neither export actually removed.

Let's wait for all exports actually removed.

Without this fix, the following crash is possible:

- export bitmap through internal Qemu NBD server
- connect a client
- shutdown Qemu

On shutdown nbd_export_close_all is called, but it actually don't wait
for nbd_trip() to finish and to release its references. So, export is
not release, and exported bitmap remains busy, and on try to remove the
bitmap (which is part of bdrv_close()) the assertion fails:

bdrv_release_dirty_bitmap_locked: Assertion `!bdrv_dirty_bitmap_busy(bitmap)' failed

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200714162234.13113-2-vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2020-07-17 14:20:57 +02:00
..
client.c nbd: Use ERRP_GUARD() 2020-07-10 15:18:09 +02:00
common.c nbd: Prepare for NBD_CMD_FLAG_FAST_ZERO 2019-09-05 16:03:13 -05:00
Makefile.objs
nbd-internal.h Include qemu/main-loop.h less 2019-08-16 13:31:52 +02:00
server.c nbd: make nbd_export_close_all() synchronous 2020-07-17 14:20:57 +02:00
trace-events trace: Remove trailing newline in events 2019-09-18 10:19:47 +01:00