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[PULL 06/12] nbd: make nbd_export_close_all() synchronous
From: |
Kevin Wolf |
Subject: |
[PULL 06/12] nbd: make nbd_export_close_all() synchronous |
Date: |
Fri, 17 Jul 2020 14:55:04 +0200 |
From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
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>
---
nbd/server.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/nbd/server.c b/nbd/server.c
index 5357f588f0..4752a6c8bc 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -102,6 +102,8 @@ struct NBDExport {
};
static QTAILQ_HEAD(, NBDExport) exports = QTAILQ_HEAD_INITIALIZER(exports);
+static QTAILQ_HEAD(, NBDExport) closed_exports =
+ QTAILQ_HEAD_INITIALIZER(closed_exports);
/* NBDExportMetaContexts represents a list of contexts to be exported,
* as selected by NBD_OPT_SET_META_CONTEXT. Also used for
@@ -1659,6 +1661,7 @@ void nbd_export_close(NBDExport *exp)
g_free(exp->name);
exp->name = NULL;
QTAILQ_REMOVE(&exports, exp, next);
+ QTAILQ_INSERT_TAIL(&closed_exports, exp, next);
}
g_free(exp->description);
exp->description = NULL;
@@ -1722,7 +1725,9 @@ void nbd_export_put(NBDExport *exp)
g_free(exp->export_bitmap_context);
}
+ QTAILQ_REMOVE(&closed_exports, exp, next);
g_free(exp);
+ aio_wait_kick();
}
}
@@ -1742,6 +1747,9 @@ void nbd_export_close_all(void)
nbd_export_close(exp);
aio_context_release(aio_context);
}
+
+ AIO_WAIT_WHILE(NULL, !(QTAILQ_EMPTY(&exports) &&
+ QTAILQ_EMPTY(&closed_exports)));
}
static int coroutine_fn nbd_co_send_iov(NBDClient *client, struct iovec *iov,
--
2.25.4
- [PULL 00/12] Block layer patches for 5.1.0-rc1, Kevin Wolf, 2020/07/17
- [PULL 01/12] vvfat: set status to odd fixes, Kevin Wolf, 2020/07/17
- [PULL 03/12] qemu-img resize: Require --shrink for shrinking all image formats, Kevin Wolf, 2020/07/17
- [PULL 02/12] Remove VXHS block device, Kevin Wolf, 2020/07/17
- [PULL 05/12] iotests/030: Reduce job speed to make race less likely, Kevin Wolf, 2020/07/17
- [PULL 06/12] nbd: make nbd_export_close_all() synchronous,
Kevin Wolf <=
- [PULL 08/12] block: Require aligned image size to avoid assertion failure, Kevin Wolf, 2020/07/17
- [PULL 04/12] crypto: use a stronger private key for tests, Kevin Wolf, 2020/07/17
- [PULL 09/12] file-posix: Allow byte-aligned O_DIRECT with NFS, Kevin Wolf, 2020/07/17
- [PULL 07/12] iotests: test shutdown when bitmap is exported through NBD, Kevin Wolf, 2020/07/17
- [PULL 10/12] file-posix: Move check_hdev_writable() up, Kevin Wolf, 2020/07/17
- [PULL 11/12] file-posix: Fix check_hdev_writable() with auto-read-only, Kevin Wolf, 2020/07/17
- [PULL 12/12] file-posix: Fix leaked fd in raw_open_common() error path, Kevin Wolf, 2020/07/17
- Re: [PULL 00/12] Block layer patches for 5.1.0-rc1, Peter Maydell, 2020/07/18