Merge tag 'ovl-update-5.10' of git://git.kernel.org/pub/scm/linux/ker…

…nel/git/mszeredi/vfs

Pull overlayfs updates from Miklos Szeredi:

 - Improve performance for certain container setups by introducing a
   "volatile" mode

 - ioctl improvements

 - continue preparation for unprivileged overlay mounts

* tag 'ovl-update-5.10' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs:
  ovl: use generic vfs_ioc_setflags_prepare() helper
  ovl: support [S|G]ETFLAGS and FS[S|G]ETXATTR ioctls for directories
  ovl: rearrange ovl_can_list()
  ovl: enumerate private xattrs
  ovl: pass ovl_fs down to functions accessing private xattrs
  ovl: drop flags argument from ovl_do_setxattr()
  ovl: adhere to the vfs_ vs. ovl_do_ conventions for xattrs
  ovl: use ovl_do_getxattr() for private xattr
  ovl: fold ovl_getxattr() into ovl_get_redirect_xattr()
  ovl: clean up ovl_getxattr() in copy_up.c
  duplicate ovl_getxattr()
  ovl: provide a mount option "volatile"
  ovl: check for incompatible features in work dir

Documentation/filesystems/overlayfs.rst

@@ -564,6 +564,25 @@ Note: the mount options index=off,nfs_export=on are conflicting for a
 read-write mount and will result in an error.
 
 
+Volatile mount
+--------------
+
+This is enabled with the "volatile" mount option.  Volatile mounts are not
+guaranteed to survive a crash.  It is strongly recommended that volatile
+mounts are only used if data written to the overlay can be recreated
+without significant effort.
+
+The advantage of mounting with the "volatile" option is that all forms of
+sync calls to the upper filesystem are omitted.
+
+When overlay is mounted with "volatile" option, the directory
+"$workdir/work/incompat/volatile" is created.  During next mount, overlay
+checks for this directory and refuses to mount if present. This is a strong
+indicator that user should throw away upper and work directories and create
+fresh one. In very limited cases where the user knows that the system has
+not crashed and contents of upperdir are intact, The "volatile" directory
+can be removed.
+
 Testsuite
 ---------
 

fs/overlayfs/copy_up.c

@@ -43,7 +43,8 @@ static bool ovl_must_copy_xattr(const char *name)
 	       !strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN);
 }
 
-int ovl_copy_xattr(struct dentry *old, struct dentry *new)
+int ovl_copy_xattr(struct super_block *sb, struct dentry *old,
+		   struct dentry *new)
 {
 	ssize_t list_size, size, value_size = 0;
 	char *buf, *name, *value = NULL;
@@ -81,7 +82,7 @@ int ovl_copy_xattr(struct dentry *old, struct dentry *new)
 		}
 		list_size -= slen;
 
-		if (ovl_is_private_xattr(name))
+		if (ovl_is_private_xattr(sb, name))
 			continue;
 retry:
 		size = vfs_getxattr(old, name, value, value_size);
@@ -128,7 +129,8 @@ int ovl_copy_xattr(struct dentry *old, struct dentry *new)
 	return error;
 }
 
-static int ovl_copy_up_data(struct path *old, struct path *new, loff_t len)
+static int ovl_copy_up_data(struct ovl_fs *ofs, struct path *old,
+			    struct path *new, loff_t len)
 {
 	struct file *old_file;
 	struct file *new_file;
@@ -218,7 +220,7 @@ static int ovl_copy_up_data(struct path *old, struct path *new, loff_t len)
 		len -= bytes;
 	}
 out:
-	if (!error)
+	if (!error && ovl_should_sync(ofs))
 		error = vfs_fsync(new_file, 0);
 	fput(new_file);
 out_fput:
@@ -354,7 +356,8 @@ int ovl_set_origin(struct dentry *dentry, struct dentry *lower,
 }
 
 /* Store file handle of @upper dir in @index dir entry */
-static int ovl_set_upper_fh(struct dentry *upper, struct dentry *index)
+static int ovl_set_upper_fh(struct ovl_fs *ofs, struct dentry *upper,
+			    struct dentry *index)
 {
 	const struct ovl_fh *fh;
 	int err;
@@ -363,7 +366,7 @@ static int ovl_set_upper_fh(struct dentry *upper, struct dentry *index)
 	if (IS_ERR(fh))
 		return PTR_ERR(fh);
 
-	err = ovl_do_setxattr(index, OVL_XATTR_UPPER, fh->buf, fh->fb.len, 0);
+	err = ovl_do_setxattr(ofs, index, OVL_XATTR_UPPER, fh->buf, fh->fb.len);
 
 	kfree(fh);
 	return err;
@@ -408,7 +411,7 @@ static int ovl_create_index(struct dentry *dentry, struct dentry *origin,
 	if (IS_ERR(temp))
 		goto free_name;
 
-	err = ovl_set_upper_fh(upper, temp);
+	err = ovl_set_upper_fh(OVL_FS(dentry->d_sb), upper, temp);
 	if (err)
 		goto out;
 
@@ -484,6 +487,7 @@ static int ovl_link_up(struct ovl_copy_up_ctx *c)
 
 static int ovl_copy_up_inode(struct ovl_copy_up_ctx *c, struct dentry *temp)
 {
+	struct ovl_fs *ofs = OVL_FS(c->dentry->d_sb);
 	int err;
 
 	/*
@@ -499,12 +503,13 @@ static int ovl_copy_up_inode(struct ovl_copy_up_ctx *c, struct dentry *temp)
 		upperpath.dentry = temp;
 
 		ovl_path_lowerdata(c->dentry, &datapath);
-		err = ovl_copy_up_data(&datapath, &upperpath, c->stat.size);
+		err = ovl_copy_up_data(ofs, &datapath, &upperpath,
+				       c->stat.size);
 		if (err)
 			return err;
 	}
 
-	err = ovl_copy_xattr(c->lowerpath.dentry, temp);
+	err = ovl_copy_xattr(c->dentry->d_sb, c->lowerpath.dentry, temp);
 	if (err)
 		return err;
 
@@ -781,9 +786,33 @@ static bool ovl_need_meta_copy_up(struct dentry *dentry, umode_t mode,
 	return true;
 }
 
+static ssize_t ovl_getxattr(struct dentry *dentry, char *name, char **value)
+{
+	ssize_t res;
+	char *buf;
+
+	res = vfs_getxattr(dentry, name, NULL, 0);
+	if (res == -ENODATA || res == -EOPNOTSUPP)
+		res = 0;
+
+	if (res > 0) {
+		buf = kzalloc(res, GFP_KERNEL);
+		if (!buf)
+			return -ENOMEM;
+
+		res = vfs_getxattr(dentry, name, buf, res);
+		if (res < 0)
+			kfree(buf);
+		else
+			*value = buf;
+	}
+	return res;
+}
+
 /* Copy up data of an inode which was copied up metadata only in the past. */
 static int ovl_copy_up_meta_inode_data(struct ovl_copy_up_ctx *c)
 {
+	struct ovl_fs *ofs = OVL_FS(c->dentry->d_sb);
 	struct path upperpath, datapath;
 	int err;
 	char *capability = NULL;
@@ -799,12 +828,12 @@ static int ovl_copy_up_meta_inode_data(struct ovl_copy_up_ctx *c)
 
 	if (c->stat.size) {
 		err = cap_size = ovl_getxattr(upperpath.dentry, XATTR_NAME_CAPS,
-					      &capability, 0);
-		if (err < 0 && err != -ENODATA)
+					      &capability);
+		if (cap_size < 0)
 			goto out;
 	}
 
-	err = ovl_copy_up_data(&datapath, &upperpath, c->stat.size);
+	err = ovl_copy_up_data(ofs, &datapath, &upperpath, c->stat.size);
 	if (err)
 		goto out_free;
 
@@ -813,14 +842,14 @@ static int ovl_copy_up_meta_inode_data(struct ovl_copy_up_ctx *c)
 	 * don't want that to happen for normal copy-up operation.
 	 */
 	if (capability) {
-		err = ovl_do_setxattr(upperpath.dentry, XATTR_NAME_CAPS,
-				      capability, cap_size, 0);
+		err = vfs_setxattr(upperpath.dentry, XATTR_NAME_CAPS,
+				   capability, cap_size, 0);
 		if (err)
 			goto out_free;
 	}
 
 
-	err = vfs_removexattr(upperpath.dentry, OVL_XATTR_METACOPY);
+	err = ovl_do_removexattr(ofs, upperpath.dentry, OVL_XATTR_METACOPY);
 	if (err)
 		goto out_free;
 

fs/overlayfs/dir.c

@@ -394,7 +394,7 @@ static struct dentry *ovl_clear_empty(struct dentry *dentry,
 	if (IS_ERR(opaquedir))
 		goto out_unlock;
 
-	err = ovl_copy_xattr(upper, opaquedir);
+	err = ovl_copy_xattr(dentry->d_sb, upper, opaquedir);
 	if (err)
 		goto out_cleanup;
 

fs/overlayfs/export.c

@@ -752,7 +752,7 @@ static struct dentry *ovl_lower_fh_to_d(struct super_block *sb,
 			goto out_err;
 	}
 	if (index) {
-		err = ovl_verify_origin(index, origin.dentry, false);
+		err = ovl_verify_origin(ofs, index, origin.dentry, false);
 		if (err)
 			goto out_err;
 	}