From: Stefan Hajnoczi <stefanha@redhat.com>

Date: Mon, 27 Jan 2020 19:01:07 +0000

Subject: [PATCH] virtiofsd: add --fd=FDNUM fd passing option

MIME-Version: 1.0

Content-Type: text/plain; charset=UTF-8

Content-Transfer-Encoding: 8bit

Although --socket-path=PATH is useful for manual invocations, management

tools typically create the UNIX domain socket themselves and pass it to

the vhost-user device backend.  This way QEMU can be launched

immediately with a valid socket.  No waiting for the vhost-user device

backend is required when fd passing is used.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

(cherry picked from commit cee8e35d4386e34bf79c3ca2aab7f7b1bb48cf8d)

---

 tools/virtiofsd/fuse_i.h        |  1 +

 tools/virtiofsd/fuse_lowlevel.c | 16 ++++++++++++----

 tools/virtiofsd/fuse_virtio.c   | 31 +++++++++++++++++++++++++------

 3 files changed, 38 insertions(+), 10 deletions(-)

diff --git a/tools/virtiofsd/fuse_i.h b/tools/virtiofsd/fuse_i.h

index 1126723d18..45995f3246 100644

--- a/tools/virtiofsd/fuse_i.h

+++ b/tools/virtiofsd/fuse_i.h

@@ -68,6 +68,7 @@ struct fuse_session {

     size_t bufsize;

     int error;

     char *vu_socket_path;

+    int   vu_listen_fd;

     int   vu_socketfd;

     struct fv_VuDev *virtio_dev;

 };

diff --git a/tools/virtiofsd/fuse_lowlevel.c b/tools/virtiofsd/fuse_lowlevel.c

index 4f4684d942..95f4db8fcf 100644

--- a/tools/virtiofsd/fuse_lowlevel.c

+++ b/tools/virtiofsd/fuse_lowlevel.c

@@ -2130,6 +2130,7 @@ static const struct fuse_opt fuse_ll_opts[] = {

     LL_OPTION("--debug", debug, 1),

     LL_OPTION("allow_root", deny_others, 1),

     LL_OPTION("--socket-path=%s", vu_socket_path, 0),

+    LL_OPTION("--fd=%d", vu_listen_fd, 0),

     FUSE_OPT_END

 };

@@ -2147,7 +2148,8 @@ void fuse_lowlevel_help(void)

      */

     printf(

         "    -o allow_root              allow access by root\n"

-        "    --socket-path=PATH         path for the vhost-user socket\n");

+        "    --socket-path=PATH         path for the vhost-user socket\n"

+        "    --fd=FDNUM                 fd number of vhost-user socket\n");

 }

 void fuse_session_destroy(struct fuse_session *se)

@@ -2191,6 +2193,7 @@ struct fuse_session *fuse_session_new(struct fuse_args *args,

         goto out1;

     }

     se->fd = -1;

+    se->vu_listen_fd = -1;

     se->conn.max_write = UINT_MAX;

     se->conn.max_readahead = UINT_MAX;

@@ -2212,8 +2215,13 @@ struct fuse_session *fuse_session_new(struct fuse_args *args,

         goto out4;

     }

-    if (!se->vu_socket_path) {

-        fprintf(stderr, "fuse: missing -o vhost_user_socket option\n");

+    if (!se->vu_socket_path && se->vu_listen_fd < 0) {

+        fuse_log(FUSE_LOG_ERR, "fuse: missing --socket-path or --fd option\n");

+        goto out4;

+    }

+    if (se->vu_socket_path && se->vu_listen_fd >= 0) {

+        fuse_log(FUSE_LOG_ERR,

+                 "fuse: --socket-path and --fd cannot be given together\n");

         goto out4;

     }

@@ -2253,7 +2261,7 @@ void fuse_session_unmount(struct fuse_session *se)

 int fuse_lowlevel_is_virtio(struct fuse_session *se)

 {

-    return se->vu_socket_path != NULL;

+    return !!se->virtio_dev;

 }

 #ifdef linux

diff --git a/tools/virtiofsd/fuse_virtio.c b/tools/virtiofsd/fuse_virtio.c

index 7e2711b504..635f87756a 100644

--- a/tools/virtiofsd/fuse_virtio.c

+++ b/tools/virtiofsd/fuse_virtio.c

@@ -638,18 +638,21 @@ int virtio_loop(struct fuse_session *se)

     return 0;

 }

-int virtio_session_mount(struct fuse_session *se)

+static int fv_create_listen_socket(struct fuse_session *se)

 {

     struct sockaddr_un un;

     mode_t old_umask;

+    /* Nothing to do if fd is already initialized */

+    if (se->vu_listen_fd >= 0) {

+        return 0;

+    }

+

     if (strlen(se->vu_socket_path) >= sizeof(un.sun_path)) {

         fuse_log(FUSE_LOG_ERR, "Socket path too long\n");

         return -1;

     }

-    se->fd = -1;

-

     /*

      * Create the Unix socket to communicate with qemu

      * based on QEMU's vhost-user-bridge

@@ -682,15 +685,31 @@ int virtio_session_mount(struct fuse_session *se)

         return -1;

     }

+    se->vu_listen_fd = listen_sock;

+    return 0;

+}

+

+int virtio_session_mount(struct fuse_session *se)

+{

+    int ret;

+

+    ret = fv_create_listen_socket(se);

+    if (ret < 0) {

+        return ret;

+    }

+

+    se->fd = -1;

+

     fuse_log(FUSE_LOG_INFO, "%s: Waiting for vhost-user socket connection...\n",

              __func__);

-    int data_sock = accept(listen_sock, NULL, NULL);

+    int data_sock = accept(se->vu_listen_fd, NULL, NULL);

     if (data_sock == -1) {

         fuse_log(FUSE_LOG_ERR, "vhost socket accept: %m\n");

-        close(listen_sock);

+        close(se->vu_listen_fd);

         return -1;

     }

-    close(listen_sock);

+    close(se->vu_listen_fd);

+    se->vu_listen_fd = -1;

     fuse_log(FUSE_LOG_INFO, "%s: Received vhost-user socket connection\n",

              __func__);