Merge remote-tracking branch 'remotes/gkurz/tags/for-upstream' into staging

This series is mostly about 9p request cancellation. It fixes a
long standing bug (read "specification violation") where the server
would send an invalid response when the client has cancelled an
in-flight request. This was causing annoying spurious EINTR returns
in linux. The fix comes with some related testing in QTEST.

Other patches are code cleanup and improvements.

# gpg: Signature made Fri 02 Feb 2018 10:16:03 GMT
# gpg:                using RSA key 71D4D5E5822F73D6
# gpg: Good signature from "Greg Kurz <groug@kaod.org>"
# gpg:                 aka "Gregory Kurz <gregory.kurz@free.fr>"
# gpg:                 aka "[jpeg image of size 3330]"
# Primary key fingerprint: B482 8BAF 9431 40CE F2A3  4910 71D4 D5E5 822F 73D6

* remotes/gkurz/tags/for-upstream:
  tests/virtio-9p: explicitly handle potential integer overflows
  tests: virtio-9p: add FLUSH operation test
  libqos/virtio: return length written into used descriptor
  tests: virtio-9p: add WRITE operation test
  tests: virtio-9p: add LOPEN operation test
  tests: virtio-9p: use the synth backend
  tests: virtio-9p: wait for completion in the test code
  tests: virtio-9p: move request tag to the test functions
  9pfs: Correctly handle cancelled requests
  9pfs: drop v9fs_register_transport()

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 24 insertions, 1 deletions

diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
index 909a611..85a1ed8 100644
--- a/hw/9pfs/9p.c
+++ b/hw/9pfs/9p.c
@@ -24,6 +24,7 @@
 #include "coth.h"
 #include "trace.h"
 #include "migration/blocker.h"
+#include "sysemu/qtest.h"
 
 int open_fd_hw;
 int total_open_fd;
@@ -630,6 +631,24 @@ static void coroutine_fn pdu_complete(V9fsPDU *pdu, ssize_t len)
     V9fsState *s = pdu->s;
     int ret;
 
+    /*
+     * The 9p spec requires that successfully cancelled pdus receive no reply.
+     * Sending a reply would confuse clients because they would
+     * assume that any EINTR is the actual result of the operation,
+     * rather than a consequence of the cancellation. However, if
+     * the operation completed (succesfully or with an error other
+     * than caused be cancellation), we do send out that reply, both
+     * for efficiency and to avoid confusing the rest of the state machine
+     * that assumes passing a non-error here will mean a successful
+     * transmission of the reply.
+     */
+    bool discard = pdu->cancelled && len == -EINTR;
+    if (discard) {
+        trace_v9fs_rcancel(pdu->tag, pdu->id);
+        pdu->size = 0;
+        goto out_notify;
+    }
+
     if (len < 0) {
         int err = -len;
         len = 7;
@@ -3485,7 +3504,8 @@ void pdu_submit(V9fsPDU *pdu, P9MsgHeader *hdr)
 }
 
 /* Returns 0 on success, 1 on failure. */
-int v9fs_device_realize_common(V9fsState *s, Error **errp)
+int v9fs_device_realize_common(V9fsState *s, const V9fsTransport *t,
+                               Error **errp)
 {
     int i, len;
     struct stat stat;
@@ -3493,6 +3513,9 @@ int v9fs_device_realize_common(V9fsState *s, Error **errp)
     V9fsPath path;
     int rc = 1;
 
+    assert(!s->transport);
+    s->transport = t;
+
     /* initialize pdu allocator */
     QLIST_INIT(&s->free_list);
     QLIST_INIT(&s->active_list);