Merge remote-tracking branch 'remotes/gkurz/tags/9p-next-2020-05-14' into staging

Changes:
- Christian Schoenebeck is now co-maintainer for 9pfs
- relax checks for O_NOATIME
- minor documentation updates

# gpg: Signature made Thu 14 May 2020 08:14:37 BST
# gpg:                using RSA key B4828BAF943140CEF2A3491071D4D5E5822F73D6
# gpg: Good signature from "Greg Kurz <groug@kaod.org>" [full]
# gpg:                 aka "Gregory Kurz <gregory.kurz@free.fr>" [full]
# gpg:                 aka "[jpeg image of size 3330]" [full]
# Primary key fingerprint: B482 8BAF 9431 40CE F2A3  4910 71D4 D5E5 822F 73D6

* remotes/gkurz/tags/9p-next-2020-05-14:
  xen-9pfs: Fix log messages of reply errors
  9pfs: local: ignore O_NOATIME if we don't have permissions
  qemu-options.hx: 9p: clarify -virtfs vs. -fsdev
  MAINTAINERS: Upgrade myself as 9pfs co-maintainer

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

4 files changed, 30 insertions, 8 deletions

diff --git a/MAINTAINERS b/MAINTAINERS
index 1f84e3ae2c..005ee98a59 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1657,7 +1657,7 @@ F: include/sysemu/balloon.h
 
 virtio-9p
 M: Greg Kurz <groug@kaod.org>
-R: Christian Schoenebeck <qemu_oss@crudebyte.com>
+M: Christian Schoenebeck <qemu_oss@crudebyte.com>
 S: Odd Fixes
 F: hw/9pfs/
 X: hw/9pfs/xen-9p*
diff --git a/hw/9pfs/9p-util.h b/hw/9pfs/9p-util.h
index 79ed6b233e..546f46dc7d 100644
--- a/hw/9pfs/9p-util.h
+++ b/hw/9pfs/9p-util.h
@@ -37,9 +37,22 @@ static inline int openat_file(int dirfd, const char *name, int flags,
 {
     int fd, serrno, ret;
 
+again:
     fd = openat(dirfd, name, flags | O_NOFOLLOW | O_NOCTTY | O_NONBLOCK,
                 mode);
     if (fd == -1) {
+        if (errno == EPERM && (flags & O_NOATIME)) {
+            /*
+             * The client passed O_NOATIME but we lack permissions to honor it.
+             * Rather than failing the open, fall back without O_NOATIME. This
+             * doesn't break the semantics on the client side, as the Linux
+             * open(2) man page notes that O_NOATIME "may not be effective on
+             * all filesystems". In particular, NFS and other network
+             * filesystems ignore it entirely.
+             */
+            flags &= ~O_NOATIME;
+            goto again;
+        }
         return -1;
     }
 
diff --git a/hw/9pfs/xen-9p-backend.c b/hw/9pfs/xen-9p-backend.c
index 18fe5b7c92..f04caabfe5 100644
--- a/hw/9pfs/xen-9p-backend.c
+++ b/hw/9pfs/xen-9p-backend.c
@@ -137,7 +137,8 @@ static ssize_t xen_9pfs_pdu_vmarshal(V9fsPDU *pdu,
     ret = v9fs_iov_vmarshal(in_sg, num, offset, 0, fmt, ap);
     if (ret < 0) {
         xen_pv_printf(&xen_9pfs->xendev, 0,
-                      "Failed to encode VirtFS request type %d\n", pdu->id + 1);
+                      "Failed to encode VirtFS reply type %d\n",
+                      pdu->id + 1);
         xen_be_set_state(&xen_9pfs->xendev, XenbusStateClosing);
         xen_9pfs_disconnect(&xen_9pfs->xendev);
     }
@@ -201,9 +202,9 @@ static void xen_9pfs_init_in_iov_from_pdu(V9fsPDU *pdu,
 
     buf_size = iov_size(ring->sg, num);
     if (buf_size  < P9_IOHDRSZ) {
-        xen_pv_printf(&xen_9pfs->xendev, 0, "Xen 9pfs request type %d"
-                "needs %zu bytes, buffer has %zu, less than minimum\n",
-                pdu->id, *size, buf_size);
+        xen_pv_printf(&xen_9pfs->xendev, 0, "Xen 9pfs reply type %d needs "
+                      "%zu bytes, buffer has %zu, less than minimum\n",
+                      pdu->id + 1, *size, buf_size);
         xen_be_set_state(&xen_9pfs->xendev, XenbusStateClosing);
         xen_9pfs_disconnect(&xen_9pfs->xendev);
     }
diff --git a/qemu-options.hx b/qemu-options.hx
index 292d4e7c0c..e2dca8a4e9 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -1542,9 +1542,17 @@ SRST
 ``-virtfs proxy,sock_fd=sock_fd,mount_tag=mount_tag [,writeout=writeout][,readonly]``
   \
 ``-virtfs synth,mount_tag=mount_tag``
-    Define a new filesystem device and expose it to the guest using a
-    virtio-9p-device. The general form of a Virtual File system
-    pass-through options are:
+    Define a new virtual filesystem device and expose it to the guest using
+    a virtio-9p-device (a.k.a. 9pfs), which essentially means that a certain
+    directory on host is made directly accessible by guest as a pass-through
+    file system by using the 9P network protocol for communication between
+    host and guests, if desired even accessible, shared by several guests
+    simultaniously.
+
+    Note that ``-virtfs`` is actually just a convenience shortcut for its
+    generalized form ``-fsdev -device virtio-9p-pci``.
+
+    The general form of pass-through file system options are:
 
     ``local``
         Accesses to the filesystem are done by QEMU.