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>

1 files changed, 13 insertions, 0 deletions

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;
     }