diff options
| author | Eric Blake <eblake@redhat.com> | 2017-11-13 13:48:57 -0600 |
|---|---|---|
| committer | Michael Roth <mdroth@linux.vnet.ibm.com> | 2017-12-06 12:33:46 -0600 |
| commit | b81833fe7d0dd56bec6f4066adec5859af01fdd6 (patch) | |
| tree | a68c0ccc330b9b2dbd2ca0978190597b0987046f | |
| parent | 0fd80ef569bf6b97a8dd1be4d0881065979fa418 (diff) | |
| download | qemu-b81833fe7d0dd56bec6f4066adec5859af01fdd6.tar.gz | |
nbd/client: Don't hard-disconnect on ESHUTDOWN from server
The NBD spec says that a server may fail any transmission request
with ESHUTDOWN when it is apparent that no further request from
the client can be successfully honored. The client is supposed
to then initiate a soft shutdown (wait for all remaining in-flight
requests to be answered, then send NBD_CMD_DISC). However, since
qemu's server never uses ESHUTDOWN errors, this code was mostly
untested since its introduction in commit b6f5d3b5.
More recently, I learned that nbdkit as the NBD server is able to
send ESHUTDOWN errors, so I finally tested this code, and noticed
that our client was special-casing ESHUTDOWN to cause a hard
shutdown (immediate disconnect, with no NBD_CMD_DISC), but only
if the server sends this error as a simple reply. Further
investigation found that commit d2febedb introduced a regression
where structured replies behave differently than simple replies -
but that the structured reply behavior is more in line with the
spec (even if we still lack code in nbd-client.c to properly quit
sending further requests). So this patch reverts the portion of
b6f5d3b5 that introduced an improper hard-disconnect special-case
at the lower level, and leaves the future enhancement of a nicer
soft-disconnect at the higher level for another day.
CC: qemu-stable@nongnu.org
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20171113194857.13933-1-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
(cherry picked from commit 01b05c66a3616d5a4adc39fc90962e9efaf791d1)
Conflicts:
nbd/client.c
*drop dep on d2febedb
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
| -rw-r--r-- | nbd/client.c | 6 |
1 files changed, 0 insertions, 6 deletions
diff --git a/nbd/client.c b/nbd/client.c index 4caff77119..f04e95542f 100644 --- a/nbd/client.c +++ b/nbd/client.c @@ -945,12 +945,6 @@ ssize_t nbd_receive_reply(QIOChannel *ioc, NBDReply *reply, Error **errp) reply->handle = ldq_be_p(buf + 8); reply->error = nbd_errno_to_system_errno(reply->error); - - if (reply->error == ESHUTDOWN) { - /* This works even on mingw which lacks a native ESHUTDOWN */ - error_setg(errp, "server shutting down"); - return -EINVAL; - } trace_nbd_receive_reply(magic, reply->error, reply->handle); if (magic != NBD_REPLY_MAGIC) { |