ovl: improve mount helpers

Move common checks into ovl_mount_dir() helper.

Create helper for looking up lower directories.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index a17702833dd040ccca0744d6b39af9891c6c70d1..592370ff453a188999c597421ed459bc752bf410 100644 (file)
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -669,24 +669,6 @@ static void ovl_unescape(char *s)
        }
 }
 
-static int ovl_mount_dir(const char *name, struct path *path)
-{
-       int err;
-       char *tmp = kstrdup(name, GFP_KERNEL);
-
-       if (!tmp)
-               return -ENOMEM;
-
-       ovl_unescape(tmp);
-       err = kern_path(tmp, LOOKUP_FOLLOW, path);
-       if (err) {
-               pr_err("overlayfs: failed to resolve '%s': %i\n", tmp, err);
-               err = -EINVAL;
-       }
-       kfree(tmp);
-       return err;
-}
-
 static bool ovl_is_allowed_fs_type(struct dentry *root)
 {
        const struct dentry_operations *dop = root->d_op;
@@ -706,6 +688,71 @@ static bool ovl_is_allowed_fs_type(struct dentry *root)
        return true;
 }
 
+static int ovl_mount_dir_noesc(const char *name, struct path *path)
+{
+       int err;
+
+       err = kern_path(name, LOOKUP_FOLLOW, path);
+       if (err) {
+               pr_err("overlayfs: failed to resolve '%s': %i\n", name, err);
+               goto out;
+       }
+       err = -EINVAL;
+       if (!ovl_is_allowed_fs_type(path->dentry)) {
+               pr_err("overlayfs: filesystem on '%s' not supported\n", name);
+               goto out_put;
+       }
+       if (!S_ISDIR(path->dentry->d_inode->i_mode)) {
+               pr_err("overlayfs: '%s' not a directory\n", name);
+               goto out_put;
+       }
+       return 0;
+
+out_put:
+       path_put(path);
+out:
+       return err;
+}
+
+static int ovl_mount_dir(const char *name, struct path *path)
+{
+       int err = -ENOMEM;
+       char *tmp = kstrdup(name, GFP_KERNEL);
+
+       if (tmp) {
+               ovl_unescape(tmp);
+               err = ovl_mount_dir_noesc(tmp, path);
+               kfree(tmp);
+       }
+       return err;
+}
+
+static int ovl_lower_dir(const char *name, struct path *path, long *namelen,
+                        int *stack_depth)
+{
+       int err;
+       struct kstatfs statfs;
+
+       err = ovl_mount_dir(name, path);
+       if (err)
+               goto out;
+
+       err = vfs_statfs(path, &statfs);
+       if (err) {
+               pr_err("overlayfs: statfs failed on '%s'\n", name);
+               goto out_put;
+       }
+       *namelen = max(*namelen, statfs.f_namelen);
+       *stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth);
+
+       return 0;
+
+out_put:
+       path_put(path);
+out:
+       return err;
+}
+
 /* Workdir should not be subdir of upperdir and vice versa */
 static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir)
 {
@@ -726,7 +773,6 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
        struct dentry *root_dentry;
        struct ovl_entry *oe;
        struct ovl_fs *ufs;
-       struct kstatfs statfs;
        struct vfsmount *mnt;
        unsigned int i;
        int err;
@@ -756,48 +802,23 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
        if (err)
                goto out_put_upperpath;
 
-       err = ovl_mount_dir(ufs->config.lowerdir, &lowerpath);
-       if (err)
-               goto out_put_workpath;
-
-       err = -EINVAL;
-       if (!S_ISDIR(upperpath.dentry->d_inode->i_mode) ||
-           !S_ISDIR(lowerpath.dentry->d_inode->i_mode) ||
-           !S_ISDIR(workpath.dentry->d_inode->i_mode)) {
-               pr_err("overlayfs: upperdir or lowerdir or workdir not a directory\n");
-               goto out_put_lowerpath;
-       }
-
        if (upperpath.mnt != workpath.mnt) {
                pr_err("overlayfs: workdir and upperdir must reside under the same mount\n");
-               goto out_put_lowerpath;
+               goto out_put_workpath;
        }
        if (!ovl_workdir_ok(workpath.dentry, upperpath.dentry)) {
                pr_err("overlayfs: workdir and upperdir must be separate subtrees\n");
-               goto out_put_lowerpath;
-       }
-
-       if (!ovl_is_allowed_fs_type(upperpath.dentry)) {
-               pr_err("overlayfs: filesystem of upperdir is not supported\n");
-               goto out_put_lowerpath;
-       }
-
-       if (!ovl_is_allowed_fs_type(lowerpath.dentry)) {
-               pr_err("overlayfs: filesystem of lowerdir is not supported\n");
-               goto out_put_lowerpath;
-       }
-
-       err = vfs_statfs(&lowerpath, &statfs);
-       if (err) {
-               pr_err("overlayfs: statfs failed on lowerpath\n");
-               goto out_put_lowerpath;
+               goto out_put_workpath;
        }
-       ufs->lower_namelen = statfs.f_namelen;
+       sb->s_stack_depth = upperpath.mnt->mnt_sb->s_stack_depth;
 
-       sb->s_stack_depth = max(upperpath.mnt->mnt_sb->s_stack_depth,
-                               lowerpath.mnt->mnt_sb->s_stack_depth) + 1;
+       err = ovl_lower_dir(ufs->config.lowerdir, &lowerpath,
+                           &ufs->lower_namelen, &sb->s_stack_depth);
+       if (err)
+               goto out_put_workpath;
 
        err = -EINVAL;
+       sb->s_stack_depth++;
        if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
                pr_err("overlayfs: maximum fs stacking depth exceeded\n");
                goto out_put_lowerpath;