[Qemu-devel] [PATCH] Remove O_NOATIME flag from 9pfs open() calls in readonly mode

["Daniel P. Berrange" <berrange@redhat.com>]

From: "Daniel P. Berrange" <berrange@redhat.com>

When 2c74c2cb4bedddbfa67628fbd5f9273b4e0e9903 added support for
the 'readonly' flag against 9p filesystems, it also made QEMU
add the O_NOATIME flag as a side-effect.

The O_NOATIME flag, however, may only be set by the file owner,
or a user with CAP_FOWNER capability.  QEMU cannot assume that
this is the case for filesytems exported to QEMU.

eg, run QEMU as non-root, and attempt to pass the host OS
filesystem through to the guest OS with readonly enable.
The result is that the guest OS cannot open any files at
all.

If O_NOATIME is really required, it should be optionally
enabled via a separate QEMU command line flag.

 * hw/9pfs/virtio-9p.c: Remove O_NOATIME

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
---
 hw/9pfs/virtio-9p.c |    1 -
 1 files changed, 0 insertions(+), 1 deletions(-)

diff --git a/hw/9pfs/virtio-9p.c b/hw/9pfs/virtio-9p.c
index e6ba6ba..f8e2c07 100644
--- a/hw/9pfs/virtio-9p.c
+++ b/hw/9pfs/virtio-9p.c
@@ -1391,7 +1391,6 @@ static void v9fs_open(void *opaque)
                 err = -EROFS;
                 goto out;
             }
-            flags |= O_NOATIME;
         }
         err = v9fs_co_open(pdu, fidp, flags);
         if (err < 0) {
-- 
1.7.7.5