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author | Eric Blake <eblake@redhat.com> | 2017-11-13 13:48:57 -0600 |
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committer | Eric Blake <eblake@redhat.com> | 2017-11-17 08:34:34 -0600 |
commit | 01b05c66a3616d5a4adc39fc90962e9efaf791d1 (patch) | |
tree | ffba83215506f5ff7e7fd255d4f189045ac310fc /nbd/client.c | |
parent | cb6b1a3fc30c52ffd94ed0b69ca5991b19651724 (diff) | |
download | qemu-01b05c66a3616d5a4adc39fc90962e9efaf791d1.zip qemu-01b05c66a3616d5a4adc39fc90962e9efaf791d1.tar.gz qemu-01b05c66a3616d5a4adc39fc90962e9efaf791d1.tar.bz2 |
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>
Diffstat (limited to 'nbd/client.c')
-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 4e15fc4..eea236c 100644 --- a/nbd/client.c +++ b/nbd/client.c @@ -996,15 +996,9 @@ int nbd_receive_reply(QIOChannel *ioc, NBDReply *reply, Error **errp) if (ret < 0) { break; } - trace_nbd_receive_simple_reply(reply->simple.error, nbd_err_lookup(reply->simple.error), reply->handle); - if (reply->simple.error == NBD_ESHUTDOWN) { - /* This works even on mingw which lacks a native ESHUTDOWN */ - error_setg(errp, "server shutting down"); - return -EINVAL; - } break; case NBD_STRUCTURED_REPLY_MAGIC: ret = nbd_receive_structured_reply_chunk(ioc, &reply->structured, errp); |