[Qemu-devel] [PATCH -V3 17/32] Implement sync support in 9p server

["Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>]

From: M. Mohan Kumar <mohan@in.ibm.com>

When wstat is called with stat field values set to 'don't touch' pattern,
9p Server interprets it as a request to guarantee that the contents of
the associated file are committed to stable storage before the Rwstat
message is returned. Implement this feature in the server side.

[jvrao@linux.vnet.ibm.com:  Proper error handling and state friendliness]

Signed-off-by: M. Mohan Kumar <mohan@in.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 hw/virtio-9p-local.c |    6 ++++++
 hw/virtio-9p.c       |   45 +++++++++++++++++++++++++++++++++++++++++++++
 hw/virtio-9p.h       |    1 +
 3 files changed, 52 insertions(+), 0 deletions(-)

diff --git a/hw/virtio-9p-local.c b/hw/virtio-9p-local.c
index 4dd6b22..4584bf6 100644
--- a/hw/virtio-9p-local.c
+++ b/hw/virtio-9p-local.c
@@ -249,6 +249,11 @@ static int local_remove(V9fsState *s, const char *path)
 }
 
 
+static int local_fsync(V9fsState *s, int fd)
+{
+    return fsync(fd);
+}
+
 static V9fsPosixFileOperations ops = {
     .lstat = local_lstat,
     .setuid = local_setuid,
@@ -277,6 +282,7 @@ static V9fsPosixFileOperations ops = {
     .chown = local_chown,
     .utime = local_utime,
     .remove = local_remove,
+    .fsync = local_fsync,
 };
 
 V9fsPosixFileOperations *virtio_9p_init_local(const char *path)
diff --git a/hw/virtio-9p.c b/hw/virtio-9p.c
index 3ddf2b9..3a5b3f0 100644
--- a/hw/virtio-9p.c
+++ b/hw/virtio-9p.c
@@ -172,6 +172,11 @@ static int posix_remove(V9fsState *s, V9fsString *path)
     return s->ops->remove(s, path->data);
 }
 
+static int posix_fsync(V9fsState *s, int fd)
+{
+    return s->ops->fsync(s, fd);
+}
+
 static void v9fs_string_init(V9fsString *str)
 {
     str->data = NULL;
@@ -1889,6 +1894,39 @@ out:
     qemu_free(vs);
 }
 
+static void v9fs_wstat_post_fsync(V9fsState *s, V9fsWstatState *vs, int err)
+{
+    if (err == -1) {
+        err = -errno;
+    }
+    v9fs_stat_free(&vs->v9stat);
+    complete_pdu(s, vs->pdu, err);
+    qemu_free(vs);
+}
+
+static int donttouch_stat(V9fsStat *stat)
+{
+    if (stat->type == -1 &&
+	stat->dev == -1 &&
+	stat->qid.type == -1 &&
+	stat->qid.version == -1 &&
+	stat->qid.path == -1 &&
+	stat->mode == -1 &&
+	stat->atime == -1 &&
+	stat->mtime == -1 &&
+	stat->length == -1 &&
+	!stat->name.size &&
+	!stat->uid.size &&
+	!stat->gid.size &&
+	!stat->muid.size &&
+	stat->n_uid == -1 &&
+	stat->n_gid == -1 &&
+	stat->n_muid == -1)
+		return 1;
+	else
+		return 0;
+}
+
 static void v9fs_wstat(V9fsState *s, V9fsPDU *pdu)
 {
     V9fsWstatState *vs;
@@ -1906,6 +1944,13 @@ static void v9fs_wstat(V9fsState *s, V9fsPDU *pdu)
         goto out;
     }
 
+    /* do we need to sync the file? */
+    if (donttouch_stat(&vs->v9stat)) {
+        err = posix_fsync(s, vs->fidp->fd);
+        v9fs_wstat_post_fsync(s, vs, err);
+        return;
+    }
+
     if (vs->v9stat.mode != -1) {
         if (vs->v9stat.mode & P9_STAT_MODE_DIR && vs->fidp->dir == NULL) {
             err = -EIO;
diff --git a/hw/virtio-9p.h b/hw/virtio-9p.h
index 3fc88a4..da0aa64 100644
--- a/hw/virtio-9p.h
+++ b/hw/virtio-9p.h
@@ -182,6 +182,7 @@ typedef struct V9fsPosixFileOpertions
     int (*fstat)(V9fsState *, int, struct stat *);
     int (*rename)(V9fsState *, const char *, const char *);
     int (*truncate)(V9fsState *, const char *, off_t);
+    int (*fsync)(V9fsState *, int);
     void *opaque;
 } V9fsPosixFileOperations;
 
-- 
1.7.0.2.323.g0d092