Add locks for vfs_mntpoint

Signed-off-by: Umer Saleem <[email protected]>

include/os/linux/zfs/sys/zfs_vfsops_os.h

@@ -69,6 +69,7 @@ typedef struct vfs {
 	boolean_t	vfs_do_relatime;
 	boolean_t	vfs_nbmand;
 	boolean_t	vfs_do_nbmand;
+	kmutex_t	vfs_mntpt_lock;
 } vfs_t;
 
 typedef struct zfs_mnt {

module/os/linux/zfs/zfs_ctldir.c

@@ -767,9 +767,6 @@ zfsctl_snapshot_path_objset(zfsvfs_t *zfsvfs, uint64_t objsetid,
 	uint64_t id, pos = 0;
 	int error = 0;
 
-	if (zfsvfs->z_vfs->vfs_mntpoint == NULL)
-		return (SET_ERROR(ENOENT));
-
 	cookie = spl_fstrans_mark();
 	snapname = kmem_alloc(ZFS_MAX_DATASET_NAME_LEN, KM_SLEEP);
 
@@ -786,8 +783,14 @@ zfsctl_snapshot_path_objset(zfsvfs_t *zfsvfs, uint64_t objsetid,
 			break;
 	}
 
-	snprintf(full_path, path_len, "%s/.zfs/snapshot/%s",
-	    zfsvfs->z_vfs->vfs_mntpoint, snapname);
+	mutex_enter(&zfsvfs->z_vfs->vfs_mntpt_lock);
+	if (zfsvfs->z_vfs->vfs_mntpoint != NULL) {
+		snprintf(full_path, path_len, "%s/.zfs/snapshot/%s",
+		    zfsvfs->z_vfs->vfs_mntpoint, snapname);
+	} else
+		error = SET_ERROR(ENOENT);
+	mutex_exit(&zfsvfs->z_vfs->vfs_mntpt_lock);
+
 out:
 	kmem_free(snapname, ZFS_MAX_DATASET_NAME_LEN);
 	spl_fstrans_unmark(cookie);
@@ -1182,21 +1185,22 @@ zfsctl_snapshot_mount(struct path *path, int flags)
 		/*
 		 * Current process is not in chroot context
 		 */
-		if (zfsvfs->z_vfs->vfs_mntpoint != NULL) {
-			char *m = kmem_zalloc(MAXPATHLEN, KM_SLEEP);
-			struct path mnt_path;
-			mnt_path.mnt = path->mnt;
-			mnt_path.dentry = path->mnt->mnt_root;
 
-			/*
-			 * Get path to current mountpoint
-			 */
-			error = get_root_path(&mnt_path, m, MAXPATHLEN);
-			if (error != 0) {
-				kmem_free(m, MAXPATHLEN);
-				goto error;
-			}
+		char *m = kmem_zalloc(MAXPATHLEN, KM_SLEEP);
+		struct path mnt_path;
+		mnt_path.mnt = path->mnt;
+		mnt_path.dentry = path->mnt->mnt_root;
 
+		/*
+		 * Get path to current mountpoint
+		 */
+		error = get_root_path(&mnt_path, m, MAXPATHLEN);
+		if (error != 0) {
+			kmem_free(m, MAXPATHLEN);
+			goto error;
+		}
+		mutex_enter(&zfsvfs->z_vfs->vfs_mntpt_lock);
+		if (zfsvfs->z_vfs->vfs_mntpoint != NULL) {
 			/*
 			 * If current mnountpoint and vfs_mntpoint are not same,
 			 * store current mountpoint in vfs_mntpoint.
@@ -1205,18 +1209,21 @@ zfsctl_snapshot_mount(struct path *path, int flags)
 				kmem_strfree(zfsvfs->z_vfs->vfs_mntpoint);
 				zfsvfs->z_vfs->vfs_mntpoint = kmem_strdup(m);
 			}
-			kmem_free(m, MAXPATHLEN);
 		}
+		mutex_exit(&zfsvfs->z_vfs->vfs_mntpt_lock);
+		kmem_free(m, MAXPATHLEN);
 	}
 
 	/*
 	 * Construct a mount point path from sb of the ctldir inode and dirent
 	 * name, instead of from d_path(), so that chroot'd process doesn't fail
 	 * on mount.zfs(8).
 	 */
+	mutex_enter(&zfsvfs->z_vfs->vfs_mntpt_lock);
 	snprintf(full_path, MAXPATHLEN, "%s/.zfs/snapshot/%s",
 	    zfsvfs->z_vfs->vfs_mntpoint ? zfsvfs->z_vfs->vfs_mntpoint : "",
 	    dname(dentry));
+	mutex_exit(&zfsvfs->z_vfs->vfs_mntpt_lock);
 
 	snprintf(options, 7, "%s",
 	    zfs_snapshot_no_setuid ? "nosuid" : "suid");

module/os/linux/zfs/zfs_vfsops.c

@@ -113,9 +113,12 @@ static void
 zfsvfs_vfs_free(vfs_t *vfsp)
 {
 	if (vfsp != NULL) {
-		if (vfsp->vfs_mntpoint != NULL)
+		mutex_enter(&vfsp->vfs_mntpt_lock);
+		if (vfsp->vfs_mntpoint != NULL) {
 			kmem_strfree(vfsp->vfs_mntpoint);
-
+		}
+		mutex_exit(&vfsp->vfs_mntpt_lock);
+		mutex_destroy(&vfsp->vfs_mntpt_lock);
 		kmem_free(vfsp, sizeof (vfs_t));
 	}
 }
@@ -197,10 +200,13 @@ zfsvfs_parse_option(char *option, int token, substring_t *args, vfs_t *vfsp)
 		vfsp->vfs_do_nbmand = B_TRUE;
 		break;
 	case TOKEN_MNTPOINT:
+		mutex_enter(&vfsp->vfs_mntpt_lock);
 		vfsp->vfs_mntpoint = match_strdup(&args[0]);
-		if (vfsp->vfs_mntpoint == NULL)
+		if (vfsp->vfs_mntpoint == NULL) {
+			mutex_exit(&vfsp->vfs_mntpt_lock);
 			return (SET_ERROR(ENOMEM));
-
+		}
+		mutex_exit(&vfsp->vfs_mntpt_lock);
 		break;
 	default:
 		break;
@@ -219,6 +225,7 @@ zfsvfs_parse_options(char *mntopts, vfs_t **vfsp)
 	int error;
 
 	tmp_vfsp = kmem_zalloc(sizeof (vfs_t), KM_SLEEP);
+	mutex_init(&tmp_vfsp->vfs_mntpt_lock, NULL, MUTEX_DEFAULT, NULL);
 
 	if (mntopts != NULL) {
 		substring_t args[MAX_OPT_ARGS];