From 77a02621812952acfde887244f6f480de1b51f95 Mon Sep 17 00:00:00 2001

From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>

Date: Sun, 4 Dec 2011 22:35:28 +0530

Subject: [PATCH 04/25] hw/9pfs: use migration blockers to prevent live

 migration when virtfs export path is mounted

Now when you try to migrate with VirtFS export path mounted, you get a proper QMP error:

(qemu) migrate tcp:localhost:4444

Migration is disabled when VirtFS export path '/tmp/' is mounted in the guest using mount_tag 'v_tmp'

(qemu)

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

---

 hw/9pfs/virtio-9p-device.c |   22 +++++++++++-----------

 hw/9pfs/virtio-9p.c        |   19 +++++++++++++++++++

 hw/9pfs/virtio-9p.h        |    5 +++--

 qerror.c                   |    5 +++++

 qerror.h                   |    3 +++

 5 files changed, 41 insertions(+), 13 deletions(-)

diff --git a/hw/9pfs/virtio-9p-device.c b/hw/9pfs/virtio-9p-device.c

index bba4c54..c9bca8b 100644

--- a/hw/9pfs/virtio-9p-device.c

+++ b/hw/9pfs/virtio-9p-device.c

@@ -33,13 +33,15 @@ static V9fsState *to_virtio_9p(VirtIODevice *vdev)

 static void virtio_9p_get_config(VirtIODevice *vdev, uint8_t *config)

 {

+    int len;

     struct virtio_9p_config *cfg;

     V9fsState *s = to_virtio_9p(vdev);

-    cfg = g_malloc0(sizeof(struct virtio_9p_config) +

-                        s->tag_len);

-    stw_raw(&cfg->tag_len, s->tag_len);

-    memcpy(cfg->tag, s->tag, s->tag_len);

+    len = strlen(s->tag);

+    cfg = g_malloc0(sizeof(struct virtio_9p_config) + len);

+    stw_raw(&cfg->tag_len, len);

+    /* We don't copy the terminating null to config space */

+    memcpy(cfg->tag, s->tag, len);

     memcpy(config, cfg, s->config_size);

     g_free(cfg);

 }

@@ -96,20 +98,18 @@ VirtIODevice *virtio_9p_init(DeviceState *dev, V9fsConf *conf)

     }

     len = strlen(conf->tag);

-    if (len > MAX_TAG_LEN) {

+    if (len > MAX_TAG_LEN - 1) {

         fprintf(stderr, "mount tag '%s' (%d bytes) is longer than "

-                "maximum (%d bytes)", conf->tag, len, MAX_TAG_LEN);

+                "maximum (%d bytes)", conf->tag, len, MAX_TAG_LEN - 1);

         exit(1);

     }

-    /* s->tag is non-NULL terminated string */

-    s->tag = g_malloc(len);

-    memcpy(s->tag, conf->tag, len);

-    s->tag_len = len;

+

+    s->tag = strdup(conf->tag);

     s->ctx.uid = -1;

     s->ops = fse->ops;

     s->vdev.get_features = virtio_9p_get_features;

-    s->config_size = sizeof(struct virtio_9p_config) + s->tag_len;

+    s->config_size = sizeof(struct virtio_9p_config) + len;

     s->vdev.get_config = virtio_9p_get_config;

     s->fid_list = NULL;

     qemu_co_rwlock_init(&s->rename_lock);

diff --git a/hw/9pfs/virtio-9p.c b/hw/9pfs/virtio-9p.c

index 1b2fc5d..32b98dd 100644

--- a/hw/9pfs/virtio-9p.c

+++ b/hw/9pfs/virtio-9p.c

@@ -23,6 +23,7 @@

 #include "virtio-9p-xattr.h"

 #include "virtio-9p-coth.h"

 #include "trace.h"

+#include "migration.h"

 int open_fd_hw;

 int total_open_fd;

@@ -373,6 +374,19 @@ static void put_fid(V9fsPDU *pdu, V9fsFidState *fidp)

      * Don't free the fid if it is in reclaim list

      */

     if (!fidp->ref && fidp->clunked) {

+        if (fidp->fid == pdu->s->root_fid) {

+            /*

+             * if the clunked fid is root fid then we

+             * have unmounted the fs on the client side.

+             * delete the migration blocker. Ideally, this

+             * should be hooked to transport close notification

+             */

+            if (pdu->s->migration_blocker) {

+                migrate_del_blocker(pdu->s->migration_blocker);

+                error_free(pdu->s->migration_blocker);

+                pdu->s->migration_blocker = NULL;

+            }

+        }

         free_fid(pdu, fidp);

     }

 }

@@ -1235,6 +1249,11 @@ static void v9fs_attach(void *opaque)

     err = offset;

     trace_v9fs_attach_return(pdu->tag, pdu->id,

                              qid.type, qid.version, qid.path);

+    s->root_fid = fid;

+    /* disable migration */

+    error_set(&s->migration_blocker, QERR_VIRTFS_FEATURE_BLOCKS_MIGRATION,

+              s->ctx.fs_root, s->tag);

+    migrate_add_blocker(s->migration_blocker);

 out:

     put_fid(pdu, fidp);

 out_nofid:

diff --git a/hw/9pfs/virtio-9p.h b/hw/9pfs/virtio-9p.h

index 7f88356..8b612da 100644

--- a/hw/9pfs/virtio-9p.h

+++ b/hw/9pfs/virtio-9p.h

@@ -246,8 +246,7 @@ typedef struct V9fsState

     V9fsFidState *fid_list;

     FileOperations *ops;

     FsContext ctx;

-    uint16_t tag_len;

-    uint8_t *tag;

+    char *tag;

     size_t config_size;

     enum p9_proto_version proto_version;

     int32_t msize;

@@ -256,6 +255,8 @@ typedef struct V9fsState

      * on rename.

      */

     CoRwlock rename_lock;

+    int32_t root_fid;

+    Error *migration_blocker;

 } V9fsState;

 typedef struct V9fsStatState {

diff --git a/qerror.c b/qerror.c

index fdf62b9..25bc91e 100644

--- a/qerror.c

+++ b/qerror.c

@@ -235,6 +235,11 @@ static const QErrorStringTable qerror_table[] = {

                      "supported by this qemu version: %(feature)",

     },

     {

+        .error_fmt = QERR_VIRTFS_FEATURE_BLOCKS_MIGRATION,

+        .desc      = "Migration is disabled when VirtFS export path '%(path)' "

+                     "is mounted in the guest using mount_tag '%(tag)'",

+    },

+    {

         .error_fmt = QERR_VNC_SERVER_FAILED,

         .desc      = "Could not start VNC server on %(target)",

     },

diff --git a/qerror.h b/qerror.h

index 2d3d43b..6414cd9 100644

--- a/qerror.h

+++ b/qerror.h

@@ -192,6 +192,9 @@ QError *qobject_to_qerror(const QObject *obj);

 #define QERR_UNKNOWN_BLOCK_FORMAT_FEATURE \

     "{ 'class': 'UnknownBlockFormatFeature', 'data': { 'device': %s, 'format': %s, 'feature': %s } }"

+#define QERR_VIRTFS_FEATURE_BLOCKS_MIGRATION \

+    "{ 'class': 'VirtFSFeatureBlocksMigration', 'data': { 'path': %s, 'tag': %s } }"

+

 #define QERR_VNC_SERVER_FAILED \

     "{ 'class': 'VNCServerFailed', 'data': { 'target': %s } }"

-- 

1.7.7.5