ovl: refactor layer parsing helpers

In preparation for new mount options to add lowerdirs one by one,
generalize ovl_parse_param_upperdir() into helper ovl_parse_layer()
that will be used for parsing a single lower layers.

Suggested-by: Miklos Szeredi <miklos@szeredi.hu>
Link: https://lore.kernel.org/r/CAJfpegt7VC94KkRtb1dfHG8+4OzwPBLYqhtc8=QFUxpFJE+=RQ@mail.gmail.com/
Signed-off-by: Amir Goldstein <amir73il@gmail.com>

diff --git a/fs/overlayfs/params.c b/fs/overlayfs/params.c
index 0bf754a69e91963f7565f8974cde0816f4c94806..88725982b6dd3f1e3232c578dd28e38328473ae4 100644 (file)
--- a/fs/overlayfs/params.c
+++ b/fs/overlayfs/params.c
@@ -43,7 +43,7 @@ module_param_named(metacopy, ovl_metacopy_def, bool, 0644);
 MODULE_PARM_DESC(metacopy,
                 "Default to on or off for the metadata only copy up feature");
 
-enum {
+enum ovl_opt {
        Opt_lowerdir,
        Opt_upperdir,
        Opt_workdir,
@@ -238,19 +238,8 @@ static int ovl_mount_dir_noesc(const char *name, struct path *path)
                pr_err("failed to resolve '%s': %i\n", name, err);
                goto out;
        }
-       err = -EINVAL;
-       if (ovl_dentry_weird(path->dentry)) {
-               pr_err("filesystem on '%s' not supported\n", name);
-               goto out_put;
-       }
-       if (!d_is_dir(path->dentry)) {
-               pr_err("'%s' not a directory\n", name);
-               goto out_put;
-       }
        return 0;
 
-out_put:
-       path_put_init(path);
 out:
        return err;
 }
@@ -268,7 +257,7 @@ static void ovl_unescape(char *s)
        }
 }
 
-static int ovl_mount_dir(const char *name, struct path *path, bool upper)
+static int ovl_mount_dir(const char *name, struct path *path)
 {
        int err = -ENOMEM;
        char *tmp = kstrdup(name, GFP_KERNEL);
@@ -276,60 +265,82 @@ static int ovl_mount_dir(const char *name, struct path *path, bool upper)
        if (tmp) {
                ovl_unescape(tmp);
                err = ovl_mount_dir_noesc(tmp, path);
-
-               if (!err && upper && path->dentry->d_flags & DCACHE_OP_REAL) {
-                       pr_err("filesystem on '%s' not supported as upperdir\n",
-                              tmp);
-                       path_put_init(path);
-                       err = -EINVAL;
-               }
                kfree(tmp);
        }
        return err;
 }
 
-static int ovl_parse_param_upperdir(const char *name, struct fs_context *fc,
-                                   bool workdir)
+static int ovl_mount_dir_check(struct fs_context *fc, const struct path *path,
+                              enum ovl_opt layer, const char *name, bool upper)
 {
-       int err;
-       struct ovl_fs *ofs = fc->s_fs_info;
-       struct ovl_config *config = &ofs->config;
-       struct ovl_fs_context *ctx = fc->fs_private;
-       struct path path;
-       char *dup;
+       if (ovl_dentry_weird(path->dentry))
+               return invalfc(fc, "filesystem on %s not supported", name);
 
-       err = ovl_mount_dir(name, &path, true);
-       if (err)
-               return err;
+       if (!d_is_dir(path->dentry))
+               return invalfc(fc, "%s is not a directory", name);
 
        /*
         * Check whether upper path is read-only here to report failures
         * early. Don't forget to recheck when the superblock is created
         * as the mount attributes could change.
         */
-       if (__mnt_is_readonly(path.mnt)) {
-               path_put(&path);
-               return -EINVAL;
+       if (upper) {
+               if (path->dentry->d_flags & DCACHE_OP_REAL)
+                       return invalfc(fc, "filesystem on %s not supported as upperdir", name);
+               if (__mnt_is_readonly(path->mnt))
+                       return invalfc(fc, "filesystem on %s is read-only", name);
        }
+       return 0;
+}
 
-       dup = kstrdup(name, GFP_KERNEL);
-       if (!dup) {
-               path_put(&path);
-               return -ENOMEM;
-       }
+static void ovl_add_layer(struct fs_context *fc, enum ovl_opt layer,
+                        struct path *path, char **pname)
+{
+       struct ovl_fs *ofs = fc->s_fs_info;
+       struct ovl_config *config = &ofs->config;
+       struct ovl_fs_context *ctx = fc->fs_private;
 
-       if (workdir) {
-               kfree(config->workdir);
-               config->workdir = dup;
-               path_put(&ctx->work);
-               ctx->work = path;
-       } else {
-               kfree(config->upperdir);
-               config->upperdir = dup;
-               path_put(&ctx->upper);
-               ctx->upper = path;
+       switch (layer) {
+       case Opt_workdir:
+               swap(config->workdir, *pname);
+               swap(ctx->work, *path);
+               break;
+       case Opt_upperdir:
+               swap(config->upperdir, *pname);
+               swap(ctx->upper, *path);
+               break;
+       default:
+               WARN_ON(1);
        }
-       return 0;
+}
+
+static int ovl_parse_layer(struct fs_context *fc, struct fs_parameter *param,
+                          enum ovl_opt layer)
+{
+       char *name = kstrdup(param->string, GFP_KERNEL);
+       bool upper = (layer == Opt_upperdir || layer == Opt_workdir);
+       struct path path;
+       int err;
+
+       if (!name)
+               return -ENOMEM;
+
+       err = ovl_mount_dir(name, &path);
+       if (err)
+               goto out_free;
+
+       err = ovl_mount_dir_check(fc, &path, layer, name, upper);
+       if (err)
+               goto out_put;
+
+       /* Store the user provided path string in ctx to show in mountinfo */
+       ovl_add_layer(fc, layer, &path, &name);
+
+out_put:
+       path_put(&path);
+out_free:
+       kfree(name);
+       return err;
 }
 
 static void ovl_reset_lowerdirs(struct ovl_fs_context *ctx)
@@ -417,7 +428,11 @@ static int ovl_parse_param_lowerdir(const char *name, struct fs_context *fc)
        for (nr = 0; nr < nr_lower; nr++, l++) {
                memset(l, 0, sizeof(*l));
 
-               err = ovl_mount_dir(iter, &l->path, false);
+               err = ovl_mount_dir(iter, &l->path);
+               if (err)
+                       goto out_put;
+
+               err = ovl_mount_dir_check(fc, &l->path, Opt_lowerdir, iter, false);
                if (err)
                        goto out_put;
 
@@ -505,10 +520,8 @@ static int ovl_parse_param(struct fs_context *fc, struct fs_parameter *param)
                err = ovl_parse_param_lowerdir(param->string, fc);
                break;
        case Opt_upperdir:
-               fallthrough;
        case Opt_workdir:
-               err = ovl_parse_param_upperdir(param->string, fc,
-                                              (Opt_workdir == opt));
+               err = ovl_parse_layer(fc, param, opt);
                break;
        case Opt_default_permissions:
                config->default_permissions = true;