hw/9pfs: Use read-write lock for protecting fid path.

On rename we take the write lock and this ensure path
doesn't change as we operate on them.

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

hw/9pfs/codir.c

@@ -65,22 +65,34 @@ void v9fs_co_rewinddir(V9fsState *s, V9fsFidState *fidp)
         });
 }
 
-int v9fs_co_mkdir(V9fsState *s, char *name, mode_t mode, uid_t uid, gid_t gid)
+int v9fs_co_mkdir(V9fsState *s, V9fsFidState *fidp, V9fsString *name,
+                  mode_t mode, uid_t uid, gid_t gid, struct stat *stbuf)
 {
     int err;
     FsCred cred;
+    V9fsString fullname;
 
     cred_init(&cred);
     cred.fc_mode = mode;
     cred.fc_uid = uid;
     cred.fc_gid = gid;
+    v9fs_string_init(&fullname);
+    qemu_co_rwlock_rdlock(&s->rename_lock);
+    v9fs_string_sprintf(&fullname, "%s/%s", fidp->path.data, name->data);
     v9fs_co_run_in_worker(
         {
-            err = s->ops->mkdir(&s->ctx, name, &cred);
+            err = s->ops->mkdir(&s->ctx, fullname.data, &cred);
             if (err < 0) {
                 err = -errno;
+            } else {
+                err = s->ops->lstat(&s->ctx, fullname.data, stbuf);
+                if (err < 0) {
+                    err = -errno;
+                }
             }
         });
+    qemu_co_rwlock_unlock(&s->rename_lock);
+    v9fs_string_free(&fullname);
     return err;
 }
 
@@ -88,6 +100,7 @@ int v9fs_co_opendir(V9fsState *s, V9fsFidState *fidp)
 {
     int err;
 
+    qemu_co_rwlock_rdlock(&s->rename_lock);
     v9fs_co_run_in_worker(
         {
             fidp->fs.dir = s->ops->opendir(&s->ctx, fidp->path.data);
@@ -97,6 +110,7 @@ int v9fs_co_opendir(V9fsState *s, V9fsFidState *fidp)
                 err = 0;
             }
         });
+    qemu_co_rwlock_unlock(&s->rename_lock);
     if (!err) {
         total_open_fd++;
         if (total_open_fd > open_fd_hw) {

hw/9pfs/cofile.c

@@ -21,6 +21,7 @@ int v9fs_co_lstat(V9fsState *s, V9fsString *path, struct stat *stbuf)
 {
     int err;
 
+    qemu_co_rwlock_rdlock(&s->rename_lock);
     v9fs_co_run_in_worker(
         {
             err = s->ops->lstat(&s->ctx, path->data, stbuf);
@@ -28,6 +29,7 @@ int v9fs_co_lstat(V9fsState *s, V9fsString *path, struct stat *stbuf)
                 err = -errno;
             }
         });
+    qemu_co_rwlock_unlock(&s->rename_lock);
     return err;
 }
 
@@ -49,6 +51,7 @@ int v9fs_co_open(V9fsState *s, V9fsFidState *fidp, int flags)
 {
     int err;
 
+    qemu_co_rwlock_rdlock(&s->rename_lock);
     v9fs_co_run_in_worker(
         {
             fidp->fs.fd = s->ops->open(&s->ctx, fidp->path.data, flags);
@@ -58,6 +61,7 @@ int v9fs_co_open(V9fsState *s, V9fsFidState *fidp, int flags)
                 err = 0;
             }
         });
+    qemu_co_rwlock_unlock(&s->rename_lock);
     if (!err) {
         total_open_fd++;
         if (total_open_fd > open_fd_hw) {
@@ -67,30 +71,48 @@ int v9fs_co_open(V9fsState *s, V9fsFidState *fidp, int flags)
     return err;
 }
 
-int v9fs_co_open2(V9fsState *s, V9fsFidState *fidp, char *fullname, gid_t gid,
-                  int flags, int mode)
+int v9fs_co_open2(V9fsState *s, V9fsFidState *fidp, V9fsString *name, gid_t gid,
+                  int flags, int mode, struct stat *stbuf)
 {
     int err;
     FsCred cred;
+    V9fsString fullname;
 
     cred_init(&cred);
     cred.fc_mode = mode & 07777;
     cred.fc_uid = fidp->uid;
     cred.fc_gid = gid;
+    v9fs_string_init(&fullname);
+    /*
+     * Hold the directory fid lock so that directory path name
+     * don't change. Read lock is fine because this fid cannot
+     * be used by any other operation.
+     */
+    qemu_co_rwlock_rdlock(&s->rename_lock);
+    v9fs_string_sprintf(&fullname, "%s/%s", fidp->path.data, name->data);
     v9fs_co_run_in_worker(
         {
-            fidp->fs.fd = s->ops->open2(&s->ctx, fullname, flags, &cred);
-            err = 0;
+            fidp->fs.fd = s->ops->open2(&s->ctx, fullname.data, flags, &cred);
             if (fidp->fs.fd == -1) {
                 err = -errno;
+            } else {
+                err = s->ops->lstat(&s->ctx, fullname.data, stbuf);
+                if (err < 0) {
+                    err = -errno;
+                    err = s->ops->close(&s->ctx, fidp->fs.fd);
+                } else {
+                    v9fs_string_copy(&fidp->path, &fullname);
+                }
             }
         });
+    qemu_co_rwlock_unlock(&s->rename_lock);
     if (!err) {
         total_open_fd++;
         if (total_open_fd > open_fd_hw) {
             v9fs_reclaim_fd(s);
         }
     }
+    v9fs_string_free(&fullname);
     return err;
 }
 
@@ -131,6 +153,7 @@ int v9fs_co_link(V9fsState *s, V9fsString *oldpath, V9fsString *newpath)
 {
     int err;
 
+    qemu_co_rwlock_rdlock(&s->rename_lock);
     v9fs_co_run_in_worker(
         {
             err = s->ops->link(&s->ctx, oldpath->data, newpath->data);
@@ -138,6 +161,7 @@ int v9fs_co_link(V9fsState *s, V9fsString *oldpath, V9fsString *newpath)
                 err = -errno;
             }
         });
+    qemu_co_rwlock_unlock(&s->rename_lock);
     return err;
 }
 

hw/9pfs/cofs.c

@@ -23,6 +23,8 @@ int v9fs_co_readlink(V9fsState *s, V9fsString *path, V9fsString *buf)
     ssize_t len;
 
     buf->data = g_malloc(PATH_MAX);
+    qemu_co_rwlock_rdlock(&s->rename_lock);
+
     v9fs_co_run_in_worker(
         {
             len = s->ops->readlink(&s->ctx, path->data,
@@ -35,6 +37,7 @@ int v9fs_co_readlink(V9fsState *s, V9fsString *path, V9fsString *buf)
                 err = -errno;
             }
         });
+    qemu_co_rwlock_unlock(&s->rename_lock);
     if (err) {
         g_free(buf->data);
         buf->data = NULL;
@@ -47,6 +50,7 @@ int v9fs_co_statfs(V9fsState *s, V9fsString *path, struct statfs *stbuf)
 {
     int err;
 
+    qemu_co_rwlock_rdlock(&s->rename_lock);
     v9fs_co_run_in_worker(
         {
             err = s->ops->statfs(&s->ctx, path->data, stbuf);
@@ -54,6 +58,7 @@ int v9fs_co_statfs(V9fsState *s, V9fsString *path, struct statfs *stbuf)
                 err = -errno;
             }
         });
+    qemu_co_rwlock_unlock(&s->rename_lock);
     return err;
 }
 
@@ -64,6 +69,7 @@ int v9fs_co_chmod(V9fsState *s, V9fsString *path, mode_t mode)
 
     cred_init(&cred);
     cred.fc_mode = mode;
+    qemu_co_rwlock_rdlock(&s->rename_lock);
     v9fs_co_run_in_worker(
         {
             err = s->ops->chmod(&s->ctx, path->data, &cred);
@@ -71,6 +77,7 @@ int v9fs_co_chmod(V9fsState *s, V9fsString *path, mode_t mode)
                 err = -errno;
             }
         });
+    qemu_co_rwlock_unlock(&s->rename_lock);
     return err;
 }
 
@@ -79,6 +86,7 @@ int v9fs_co_utimensat(V9fsState *s, V9fsString *path,
 {
     int err;
 
+    qemu_co_rwlock_rdlock(&s->rename_lock);
     v9fs_co_run_in_worker(
         {
             err = s->ops->utimensat(&s->ctx, path->data, times);
@@ -86,6 +94,7 @@ int v9fs_co_utimensat(V9fsState *s, V9fsString *path,
                 err = -errno;
             }
         });
+    qemu_co_rwlock_unlock(&s->rename_lock);
     return err;
 }
 
@@ -97,6 +106,7 @@ int v9fs_co_chown(V9fsState *s, V9fsString *path, uid_t uid, gid_t gid)
     cred_init(&cred);
     cred.fc_uid = uid;
     cred.fc_gid = gid;
+    qemu_co_rwlock_rdlock(&s->rename_lock);
     v9fs_co_run_in_worker(
         {
             err = s->ops->chown(&s->ctx, path->data, &cred);
@@ -104,6 +114,7 @@ int v9fs_co_chown(V9fsState *s, V9fsString *path, uid_t uid, gid_t gid)
                 err = -errno;
             }
         });
+    qemu_co_rwlock_unlock(&s->rename_lock);
     return err;
 }
 
@@ -111,6 +122,7 @@ int v9fs_co_truncate(V9fsState *s, V9fsString *path, off_t size)
 {
     int err;
 
+    qemu_co_rwlock_rdlock(&s->rename_lock);
     v9fs_co_run_in_worker(
         {
             err = s->ops->truncate(&s->ctx, path->data, size);
@@ -118,27 +130,39 @@ int v9fs_co_truncate(V9fsState *s, V9fsString *path, off_t size)
                 err = -errno;
             }
         });
+    qemu_co_rwlock_unlock(&s->rename_lock);
     return err;
 }
 
-int v9fs_co_mknod(V9fsState *s, V9fsString *path, uid_t uid,
-                  gid_t gid, dev_t dev, mode_t mode)
+int v9fs_co_mknod(V9fsState *s, V9fsFidState *fidp, V9fsString *name, uid_t uid,
+                  gid_t gid, dev_t dev, mode_t mode, struct stat *stbuf)
 {
     int err;
     FsCred cred;
+    V9fsString fullname;
 
     cred_init(&cred);
     cred.fc_uid  = uid;
     cred.fc_gid  = gid;
     cred.fc_mode = mode;
     cred.fc_rdev = dev;
+    v9fs_string_init(&fullname);
+    qemu_co_rwlock_rdlock(&s->rename_lock);
+    v9fs_string_sprintf(&fullname, "%s/%s", fidp->path.data, name->data);
     v9fs_co_run_in_worker(
         {
-            err = s->ops->mknod(&s->ctx, path->data, &cred);
+            err = s->ops->mknod(&s->ctx, fullname.data, &cred);
             if (err < 0) {
                 err = -errno;
+            } else {
+                err = s->ops->lstat(&s->ctx, fullname.data, stbuf);
+                if (err < 0) {
+                    err = -errno;
+                }
             }
         });
+    qemu_co_rwlock_unlock(&s->rename_lock);
+    v9fs_string_free(&fullname);
     return err;
 }
 
@@ -146,6 +170,7 @@ int v9fs_co_remove(V9fsState *s, V9fsString *path)
 {
     int err;
 
+    qemu_co_rwlock_rdlock(&s->rename_lock);
     v9fs_co_run_in_worker(
         {
             err = s->ops->remove(&s->ctx, path->data);
@@ -153,6 +178,7 @@ int v9fs_co_remove(V9fsState *s, V9fsString *path)
                 err = -errno;
             }
         });
+    qemu_co_rwlock_unlock(&s->rename_lock);
     return err;
 }
 
@@ -170,22 +196,34 @@ int v9fs_co_rename(V9fsState *s, V9fsString *oldpath, V9fsString *newpath)
     return err;
 }
 
-int v9fs_co_symlink(V9fsState *s, V9fsFidState *fidp,
-                    const char *oldpath, const char *newpath, gid_t gid)
+int v9fs_co_symlink(V9fsState *s, V9fsFidState *dfidp, V9fsString *name,
+                    const char *oldpath, gid_t gid, struct stat *stbuf)
 {
     int err;
     FsCred cred;
+    V9fsString fullname;
+
 
     cred_init(&cred);
-    cred.fc_uid = fidp->uid;
+    cred.fc_uid = dfidp->uid;
     cred.fc_gid = gid;
     cred.fc_mode = 0777;
+    v9fs_string_init(&fullname);
+    qemu_co_rwlock_rdlock(&s->rename_lock);
+    v9fs_string_sprintf(&fullname, "%s/%s", dfidp->path.data, name->data);
     v9fs_co_run_in_worker(
         {
-            err = s->ops->symlink(&s->ctx, oldpath, newpath, &cred);
+            err = s->ops->symlink(&s->ctx, oldpath, fullname.data, &cred);
             if (err < 0) {
                 err = -errno;
+            } else {
+                err = s->ops->lstat(&s->ctx, fullname.data, stbuf);
+                if (err < 0) {
+                    err = -errno;
+                }
             }
         });
+    qemu_co_rwlock_unlock(&s->rename_lock);
+    v9fs_string_free(&fullname);
     return err;
 }

hw/9pfs/coxattr.c

@@ -21,6 +21,7 @@ int v9fs_co_llistxattr(V9fsState *s, V9fsString *path, void *value, size_t size)
 {
     int err;
 
+    qemu_co_rwlock_rdlock(&s->rename_lock);
     v9fs_co_run_in_worker(
         {
             err = s->ops->llistxattr(&s->ctx, path->data, value, size);
@@ -28,6 +29,7 @@ int v9fs_co_llistxattr(V9fsState *s, V9fsString *path, void *value, size_t size)
                 err = -errno;
             }
         });
+    qemu_co_rwlock_unlock(&s->rename_lock);
     return err;
 }
 
@@ -37,6 +39,7 @@ int v9fs_co_lgetxattr(V9fsState *s, V9fsString *path,
 {
     int err;
 
+    qemu_co_rwlock_rdlock(&s->rename_lock);
     v9fs_co_run_in_worker(
         {
             err = s->ops->lgetxattr(&s->ctx, path->data,
@@ -46,6 +49,7 @@ int v9fs_co_lgetxattr(V9fsState *s, V9fsString *path,
                 err = -errno;
             }
         });
+    qemu_co_rwlock_unlock(&s->rename_lock);
     return err;
 }
 
@@ -55,6 +59,7 @@ int v9fs_co_lsetxattr(V9fsState *s, V9fsString *path,
 {
     int err;
 
+    qemu_co_rwlock_rdlock(&s->rename_lock);
     v9fs_co_run_in_worker(
         {
             err = s->ops->lsetxattr(&s->ctx, path->data,
@@ -64,6 +69,7 @@ int v9fs_co_lsetxattr(V9fsState *s, V9fsString *path,
                 err = -errno;
             }
         });
+    qemu_co_rwlock_unlock(&s->rename_lock);
     return err;
 }
 
@@ -72,6 +78,7 @@ int v9fs_co_lremovexattr(V9fsState *s, V9fsString *path,
 {
     int err;
 
+    qemu_co_rwlock_rdlock(&s->rename_lock);
     v9fs_co_run_in_worker(
         {
             err = s->ops->lremovexattr(&s->ctx, path->data,
@@ -80,5 +87,6 @@ int v9fs_co_lremovexattr(V9fsState *s, V9fsString *path,
                 err = -errno;
             }
         });
+    qemu_co_rwlock_unlock(&s->rename_lock);
     return err;
 }

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

@@ -71,23 +71,25 @@ extern int v9fs_co_truncate(V9fsState *, V9fsString *, off_t);
 extern int v9fs_co_llistxattr(V9fsState *, V9fsString *, void *, size_t);
 extern int v9fs_co_lgetxattr(V9fsState *, V9fsString *,
                              V9fsString *, void *, size_t);
-extern int v9fs_co_mknod(V9fsState *, V9fsString *, uid_t,
-                         gid_t, dev_t, mode_t);
-extern int v9fs_co_mkdir(V9fsState *, char *, mode_t, uid_t, gid_t);
+extern int v9fs_co_mknod(V9fsState *, V9fsFidState *, V9fsString *, uid_t,
+                         gid_t, dev_t, mode_t, struct stat *);
+extern int v9fs_co_mkdir(V9fsState *, V9fsFidState *, V9fsString *,
+                         mode_t, uid_t, gid_t, struct stat *);
 extern int v9fs_co_remove(V9fsState *, V9fsString *);
 extern int v9fs_co_rename(V9fsState *, V9fsString *, V9fsString *);
 extern int v9fs_co_fstat(V9fsState *, int, struct stat *);
 extern int v9fs_co_opendir(V9fsState *, V9fsFidState *);
 extern int v9fs_co_open(V9fsState *, V9fsFidState *, int);
-extern int v9fs_co_open2(V9fsState *, V9fsFidState *, char *, gid_t, int, int);
+extern int v9fs_co_open2(V9fsState *, V9fsFidState *, V9fsString *,
+                         gid_t, int, int, struct stat *);
 extern int v9fs_co_lsetxattr(V9fsState *, V9fsString *, V9fsString *,
                              void *, size_t, int);
 extern int v9fs_co_lremovexattr(V9fsState *, V9fsString *, V9fsString *);
 extern int v9fs_co_closedir(V9fsState *, DIR *);
 extern int v9fs_co_close(V9fsState *, int);
 extern int v9fs_co_fsync(V9fsState *, V9fsFidState *, int);
-extern int v9fs_co_symlink(V9fsState *, V9fsFidState *, const char *,
-                           const char *, gid_t);
+extern int v9fs_co_symlink(V9fsState *, V9fsFidState *, V9fsString *,
+                           const char *, gid_t, struct stat *);
 extern int v9fs_co_link(V9fsState *, V9fsString *, V9fsString *);
 extern int v9fs_co_pwritev(V9fsState *, V9fsFidState *,
                            struct iovec *, int, int64_t);

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

@@ -131,6 +131,7 @@ VirtIODevice *virtio_9p_init(DeviceState *dev, V9fsConf *conf)
                         s->tag_len;
     s->vdev.get_config = virtio_9p_get_config;
     s->fid_list = NULL;
+    qemu_co_rwlock_init(&s->rename_lock);
 
     if (v9fs_init_worker_threads() < 0) {
         fprintf(stderr, "worker thread initialization failed\n");

hw/9pfs/virtio-9p.c

@@ -1582,7 +1582,6 @@ static void v9fs_lcreate(void *opaque)
     gid_t gid;
     ssize_t err = 0;
     ssize_t offset = 7;
-    V9fsString fullname;
     V9fsString name;
     V9fsFidState *fidp;
     struct stat stbuf;
@@ -1590,7 +1589,6 @@ static void v9fs_lcreate(void *opaque)
     int32_t iounit;
     V9fsPDU *pdu = opaque;
 
-    v9fs_string_init(&fullname);
     pdu_unmarshal(pdu, offset, "dsddd", &dfid, &name, &flags,
                   &mode, &gid);
 
@@ -1599,12 +1597,12 @@ static void v9fs_lcreate(void *opaque)
         err = -ENOENT;
         goto out_nofid;
     }
-    v9fs_string_sprintf(&fullname, "%s/%s", fidp->path.data, name.data);
 
     /* Ignore direct disk access hint until the server supports it. */
     flags &= ~O_DIRECT;
 
-    err = v9fs_co_open2(pdu->s, fidp, fullname.data, gid, flags, mode);
+    err = v9fs_co_open2(pdu->s, fidp, &name, gid,
+                        flags | O_CREAT, mode, &stbuf);
     if (err < 0) {
         goto out;
     }
@@ -1617,17 +1615,7 @@ static void v9fs_lcreate(void *opaque)
          */
         fidp->flags |= FID_NON_RECLAIMABLE;
     }
-    iounit =  get_iounit(pdu->s, &fullname);
-
-    err = v9fs_co_lstat(pdu->s, &fullname, &stbuf);
-    if (err < 0) {
-        fidp->fid_type = P9_FID_NONE;
-        if (fidp->fs.fd > 0) {
-            v9fs_co_close(pdu->s, fidp->fs.fd);
-        }
-        goto out;
-    }
-    v9fs_string_copy(&fidp->path, &fullname);
+    iounit =  get_iounit(pdu->s, &fidp->path);
     stat_to_qid(&stbuf, &qid);
     offset += pdu_marshal(pdu, offset, "Qd", &qid, iounit);
     err = offset;
@@ -1636,7 +1624,6 @@ out:
 out_nofid:
     complete_pdu(pdu->s, pdu, err);
     v9fs_string_free(&name);
-    v9fs_string_free(&fullname);
 }
 
 static void v9fs_fsync(void *opaque)
@@ -2102,11 +2089,12 @@ static void v9fs_create(void *opaque)
         goto out;
     }
     if (perm & P9_STAT_MODE_DIR) {
-        err = v9fs_co_mkdir(pdu->s, fullname.data, perm & 0777,
-                            fidp->uid, -1);
+        err = v9fs_co_mkdir(pdu->s, fidp, &name, perm & 0777,
+                            fidp->uid, -1, &stbuf);
         if (err < 0) {
             goto out;
         }
+        v9fs_string_sprintf(&fullname, "%s/%s", fidp->path.data, name.data);
         v9fs_string_copy(&fidp->path, &fullname);
         err = v9fs_co_opendir(pdu->s, fidp);
         if (err < 0) {
@@ -2114,11 +2102,13 @@ static void v9fs_create(void *opaque)
         }
         fidp->fid_type = P9_FID_DIR;
     } else if (perm & P9_STAT_MODE_SYMLINK) {
-        err = v9fs_co_symlink(pdu->s, fidp, extension.data,
-                              fullname.data, -1);
+        err = v9fs_co_symlink(pdu->s, fidp, &name,
+                              extension.data, -1 , &stbuf);
         if (err < 0) {
             goto out;
         }
+        v9fs_string_sprintf(&fullname, "%s/%s", fidp->path.data, name.data);
+        v9fs_string_copy(&fidp->path, &fullname);
     } else if (perm & P9_STAT_MODE_LINK) {
         int32_t nfid = atoi(extension.data);
         V9fsFidState *nfidp = get_fid(pdu->s, nfid);
@@ -2126,12 +2116,19 @@ static void v9fs_create(void *opaque)
             err = -EINVAL;
             goto out;
         }
+        v9fs_string_sprintf(&fullname, "%s/%s", fidp->path.data, name.data);
         err = v9fs_co_link(pdu->s, &nfidp->path, &fullname);
+        put_fid(pdu->s, nfidp);
         if (err < 0) {
-            put_fid(pdu->s, nfidp);
             goto out;
         }
-        put_fid(pdu->s, nfidp);
+        v9fs_string_sprintf(&fullname, "%s/%s", fidp->path.data, name.data);
+        v9fs_string_copy(&fidp->path, &fullname);
+        err = v9fs_co_lstat(pdu->s, &fidp->path, &stbuf);
+        if (err < 0) {
+            fidp->fid_type = P9_FID_NONE;
+            goto out;
+        }
     } else if (perm & P9_STAT_MODE_DEVICE) {
         char ctype;
         uint32_t major, minor;
@@ -2155,26 +2152,32 @@ static void v9fs_create(void *opaque)
         }
 
         nmode |= perm & 0777;
-        err = v9fs_co_mknod(pdu->s, &fullname, fidp->uid, -1,
-                            makedev(major, minor), nmode);
+        err = v9fs_co_mknod(pdu->s, fidp, &name, fidp->uid, -1,
+                            makedev(major, minor), nmode, &stbuf);
         if (err < 0) {
             goto out;
         }
+        v9fs_string_sprintf(&fullname, "%s/%s", fidp->path.data, name.data);
+        v9fs_string_copy(&fidp->path, &fullname);
     } else if (perm & P9_STAT_MODE_NAMED_PIPE) {
-        err = v9fs_co_mknod(pdu->s, &fullname, fidp->uid, -1,
-                            0, S_IFIFO | (perm & 0777));
+        err = v9fs_co_mknod(pdu->s, fidp, &name, fidp->uid, -1,
+                            0, S_IFIFO | (perm & 0777), &stbuf);
         if (err < 0) {
             goto out;
         }
+        v9fs_string_sprintf(&fullname, "%s/%s", fidp->path.data, name.data);
+        v9fs_string_copy(&fidp->path, &fullname);
     } else if (perm & P9_STAT_MODE_SOCKET) {
-        err = v9fs_co_mknod(pdu->s, &fullname, fidp->uid, -1,
-                            0, S_IFSOCK | (perm & 0777));
+        err = v9fs_co_mknod(pdu->s, fidp, &name, fidp->uid, -1,
+                            0, S_IFSOCK | (perm & 0777), &stbuf);
         if (err < 0) {
             goto out;
         }
+        v9fs_string_sprintf(&fullname, "%s/%s", fidp->path.data, name.data);
+        v9fs_string_copy(&fidp->path, &fullname);
     } else {
-        err = v9fs_co_open2(pdu->s, fidp, fullname.data, -1,
-                            omode_to_uflags(mode)|O_CREAT, perm);
+        err = v9fs_co_open2(pdu->s, fidp, &name, -1,
+                            omode_to_uflags(mode)|O_CREAT, perm, &stbuf);
         if (err < 0) {
             goto out;
         }
@@ -2188,16 +2191,7 @@ static void v9fs_create(void *opaque)
             fidp->flags |= FID_NON_RECLAIMABLE;
         }
     }
-    err = v9fs_co_lstat(pdu->s, &fullname, &stbuf);
-    if (err < 0) {
-        fidp->fid_type = P9_FID_NONE;
-        if (fidp->fs.fd) {
-            v9fs_co_close(pdu->s, fidp->fs.fd);
-        }
-        goto out;
-    }
     iounit = get_iounit(pdu->s, &fidp->path);
-    v9fs_string_copy(&fidp->path, &fullname);
     stat_to_qid(&stbuf, &qid);
     offset += pdu_marshal(pdu, offset, "Qd", &qid, iounit);
     err = offset;
@@ -2215,7 +2209,6 @@ static void v9fs_symlink(void *opaque)
     V9fsPDU *pdu = opaque;
     V9fsString name;
     V9fsString symname;
-    V9fsString fullname;
     V9fsFidState *dfidp;
     V9fsQID qid;
     struct stat stbuf;
@@ -2224,7 +2217,6 @@ static void v9fs_symlink(void *opaque)
     gid_t gid;
     size_t offset = 7;
 
-    v9fs_string_init(&fullname);
     pdu_unmarshal(pdu, offset, "dssd", &dfid, &name, &symname, &gid);
 
     dfidp = get_fid(pdu->s, dfid);
@@ -2232,13 +2224,7 @@ static void v9fs_symlink(void *opaque)
         err = -EINVAL;
         goto out_nofid;
     }
-
-    v9fs_string_sprintf(&fullname, "%s/%s", dfidp->path.data, name.data);
-    err = v9fs_co_symlink(pdu->s, dfidp, symname.data, fullname.data, gid);
-    if (err < 0) {
-        goto out;
-    }
-    err = v9fs_co_lstat(pdu->s, &fullname, &stbuf);
+    err = v9fs_co_symlink(pdu->s, dfidp, &name, symname.data, gid, &stbuf);
     if (err < 0) {
         goto out;
     }
@@ -2251,7 +2237,6 @@ out_nofid:
     complete_pdu(pdu->s, pdu, err);
     v9fs_string_free(&name);
     v9fs_string_free(&symname);
-    v9fs_string_free(&fullname);
 }
 
 static void v9fs_flush(void *opaque)
@@ -2469,7 +2454,9 @@ static void v9fs_rename(void *opaque)
     }
     BUG_ON(fidp->fid_type != P9_FID_NONE);
 
+    qemu_co_rwlock_wrlock(&s->rename_lock);
     err = v9fs_complete_rename(s, fidp, newdirfid, &name);
+    qemu_co_rwlock_unlock(&s->rename_lock);
     if (!err) {
         err = offset;
     }
@@ -2551,7 +2538,9 @@ static void v9fs_renameat(void *opaque)
     pdu_unmarshal(pdu, offset, "dsds", &olddirfid,
                   &old_name, &newdirfid, &new_name);
 
+    qemu_co_rwlock_wrlock(&s->rename_lock);
     err = v9fs_complete_renameat(s, olddirfid, &old_name, newdirfid, &new_name);
+    qemu_co_rwlock_unlock(&s->rename_lock);
     if (!err) {
         err = offset;
     }
@@ -2735,12 +2724,10 @@ static void v9fs_mknod(void *opaque)
     size_t offset = 7;
     V9fsString name;
     struct stat stbuf;
-    V9fsString fullname;
     V9fsFidState *fidp;
     V9fsPDU *pdu = opaque;
     V9fsState *s = pdu->s;
 
-    v9fs_string_init(&fullname);
     pdu_unmarshal(pdu, offset, "dsdddd", &fid, &name, &mode,
                   &major, &minor, &gid);
 
@@ -2749,13 +2736,8 @@ static void v9fs_mknod(void *opaque)
         err = -ENOENT;
         goto out_nofid;
     }
-    v9fs_string_sprintf(&fullname, "%s/%s", fidp->path.data, name.data);
-    err = v9fs_co_mknod(s, &fullname, fidp->uid, gid,
-                        makedev(major, minor), mode);
-    if (err < 0) {
-        goto out;
-    }
-    err = v9fs_co_lstat(s, &fullname, &stbuf);
+    err = v9fs_co_mknod(s, fidp, &name, fidp->uid, gid,
+                        makedev(major, minor), mode, &stbuf);
     if (err < 0) {
         goto out;
     }
@@ -2766,7 +2748,6 @@ out:
     put_fid(s, fidp);
 out_nofid:
     complete_pdu(s, pdu, err);
-    v9fs_string_free(&fullname);
     v9fs_string_free(&name);
 }
 
@@ -2867,14 +2848,13 @@ static void v9fs_mkdir(void *opaque)
     size_t offset = 7;
     int32_t fid;
     struct stat stbuf;
-    V9fsString name, fullname;
     V9fsQID qid;
+    V9fsString name;
     V9fsFidState *fidp;
     gid_t gid;
     int mode;
     int err = 0;
 
-    v9fs_string_init(&fullname);
     pdu_unmarshal(pdu, offset, "dsdd", &fid, &name, &mode, &gid);
 
     fidp = get_fid(pdu->s, fid);
@@ -2882,12 +2862,7 @@ static void v9fs_mkdir(void *opaque)
         err = -ENOENT;
         goto out_nofid;
     }
-    v9fs_string_sprintf(&fullname, "%s/%s", fidp->path.data, name.data);
-    err = v9fs_co_mkdir(pdu->s, fullname.data, mode, fidp->uid, gid);
-    if (err < 0) {
-        goto out;
-    }
-    err = v9fs_co_lstat(pdu->s, &fullname, &stbuf);
+    err = v9fs_co_mkdir(pdu->s, fidp, &name, mode, fidp->uid, gid, &stbuf);
     if (err < 0) {
         goto out;
     }
@@ -2898,7 +2873,6 @@ out:
     put_fid(pdu->s, fidp);
 out_nofid:
     complete_pdu(pdu->s, pdu, err);
-    v9fs_string_free(&fullname);
     v9fs_string_free(&name);
 }
 

hw/9pfs/virtio-9p.h

@@ -8,6 +8,8 @@
 #include <sys/resource.h>
 #include "hw/virtio.h"
 #include "fsdev/file-op-9p.h"
+#include "qemu-thread.h"
+#include "qemu-coroutine.h"
 
 /* The feature bitmap for virtio 9P */
 /* The mount point is specified in a config variable */
@@ -237,6 +239,11 @@ typedef struct V9fsState
     size_t config_size;
     enum p9_proto_version proto_version;
     int32_t msize;
+    /*
+     * lock ensuring atomic path update
+     * on rename.
+     */
+    CoRwlock rename_lock;
 } V9fsState;
 
 typedef struct V9fsStatState {