ovl: store enum redirect_mode in config instead of a string

Do all the logic to set the mode during mount options parsing and
do not keep the option string around.

Use a constant_table to translate from enum redirect mode to string
in preperation for new mount api option parsing.

The mount option "off" is translated to either "follow" or "nofollow",
depending on the "redirect_always_follow" build/module config, so
in effect, there are only three possible redirect modes.

This results in a minor change to the string that is displayed
in show_options() - when redirect_dir is enabled by default and the user
mounts with the option "redirect_dir=off", instead of displaying the mode
"redirect_dir=off" in show_options(), the displayed mode will be either
"redirect_dir=follow" or "redirect_dir=nofollow", depending on the value
of "redirect_always_follow" build/module config.

The displayed mode reflects the effective mode, so mounting overlayfs
again with the dispalyed redirect_dir option will result with the same
effective and displayed mode.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>

1 files changed, 71 insertions, 58 deletions

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 5bcb26528408..5a84af92c91e 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -244,7 +244,6 @@ static void ovl_free_fs(struct ovl_fs *ofs)
 	kfree(ofs->config.lowerdir);
 	kfree(ofs->config.upperdir);
 	kfree(ofs->config.workdir);
-	kfree(ofs->config.redirect_mode);
 	if (ofs->creator_cred)
 		put_cred(ofs->creator_cred);
 	kfree(ofs);
@@ -330,9 +329,24 @@ static bool ovl_force_readonly(struct ovl_fs *ofs)
 	return (!ovl_upper_mnt(ofs) || !ofs->workdir);
 }
 
-static const char *ovl_redirect_mode_def(void)
+static const struct constant_table ovl_parameter_redirect_dir[] = {
+	{ "off",	OVL_REDIRECT_OFF      },
+	{ "follow",	OVL_REDIRECT_FOLLOW   },
+	{ "nofollow",	OVL_REDIRECT_NOFOLLOW },
+	{ "on",		OVL_REDIRECT_ON       },
+	{}
+};
+
+static const char *ovl_redirect_mode(struct ovl_config *config)
 {
-	return ovl_redirect_dir_def ? "on" : "off";
+	return ovl_parameter_redirect_dir[config->redirect_mode].name;
+}
+
+static int ovl_redirect_mode_def(void)
+{
+	return ovl_redirect_dir_def ? OVL_REDIRECT_ON :
+		ovl_redirect_always_follow ? OVL_REDIRECT_FOLLOW :
+					     OVL_REDIRECT_NOFOLLOW;
 }
 
 static const struct constant_table ovl_parameter_xino[] = {
@@ -372,8 +386,9 @@ static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
 	}
 	if (ofs->config.default_permissions)
 		seq_puts(m, ",default_permissions");
-	if (strcmp(ofs->config.redirect_mode, ovl_redirect_mode_def()) != 0)
-		seq_printf(m, ",redirect_dir=%s", ofs->config.redirect_mode);
+	if (ofs->config.redirect_mode != ovl_redirect_mode_def())
+		seq_printf(m, ",redirect_dir=%s",
+			   ovl_redirect_mode(&ofs->config));
 	if (ofs->config.index != ovl_index_def)
 		seq_printf(m, ",index=%s", ofs->config.index ? "on" : "off");
 	if (!ofs->config.uuid)
@@ -431,7 +446,10 @@ enum {
 	OPT_UPPERDIR,
 	OPT_WORKDIR,
 	OPT_DEFAULT_PERMISSIONS,
-	OPT_REDIRECT_DIR,
+	OPT_REDIRECT_DIR_ON,
+	OPT_REDIRECT_DIR_OFF,
+	OPT_REDIRECT_DIR_FOLLOW,
+	OPT_REDIRECT_DIR_NOFOLLOW,
 	OPT_INDEX_ON,
 	OPT_INDEX_OFF,
 	OPT_UUID_ON,
@@ -453,7 +471,10 @@ static const match_table_t ovl_tokens = {
 	{OPT_UPPERDIR,			"upperdir=%s"},
 	{OPT_WORKDIR,			"workdir=%s"},
 	{OPT_DEFAULT_PERMISSIONS,	"default_permissions"},
-	{OPT_REDIRECT_DIR,		"redirect_dir=%s"},
+	{OPT_REDIRECT_DIR_ON,		"redirect_dir=on"},
+	{OPT_REDIRECT_DIR_OFF,		"redirect_dir=off"},
+	{OPT_REDIRECT_DIR_FOLLOW,	"redirect_dir=follow"},
+	{OPT_REDIRECT_DIR_NOFOLLOW,	"redirect_dir=nofollow"},
 	{OPT_INDEX_ON,			"index=on"},
 	{OPT_INDEX_OFF,			"index=off"},
 	{OPT_USERXATTR,			"userxattr"},
@@ -493,40 +514,12 @@ static char *ovl_next_opt(char **s)
 	return sbegin;
 }
 
-static int ovl_parse_redirect_mode(struct ovl_config *config, const char *mode)
-{
-	if (strcmp(mode, "on") == 0) {
-		config->redirect_dir = true;
-		/*
-		 * Does not make sense to have redirect creation without
-		 * redirect following.
-		 */
-		config->redirect_follow = true;
-	} else if (strcmp(mode, "follow") == 0) {
-		config->redirect_follow = true;
-	} else if (strcmp(mode, "off") == 0) {
-		if (ovl_redirect_always_follow)
-			config->redirect_follow = true;
-	} else if (strcmp(mode, "nofollow") != 0) {
-		pr_err("bad mount option \"redirect_dir=%s\"\n",
-		       mode);
-		return -EINVAL;
-	}
-
-	return 0;
-}
-
 static int ovl_parse_opt(char *opt, struct ovl_config *config)
 {
 	char *p;
-	int err;
 	bool metacopy_opt = false, redirect_opt = false;
 	bool nfs_export_opt = false, index_opt = false;
 
-	config->redirect_mode = kstrdup(ovl_redirect_mode_def(), GFP_KERNEL);
-	if (!config->redirect_mode)
-		return -ENOMEM;
-
 	while ((p = ovl_next_opt(&opt)) != NULL) {
 		int token;
 		substring_t args[MAX_OPT_ARGS];
@@ -561,11 +554,25 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config)
 			config->default_permissions = true;
 			break;
 
-		case OPT_REDIRECT_DIR:
-			kfree(config->redirect_mode);
-			config->redirect_mode = match_strdup(&args[0]);
-			if (!config->redirect_mode)
-				return -ENOMEM;
+		case OPT_REDIRECT_DIR_ON:
+			config->redirect_mode = OVL_REDIRECT_ON;
+			redirect_opt = true;
+			break;
+
+		case OPT_REDIRECT_DIR_OFF:
+			config->redirect_mode = ovl_redirect_always_follow ?
+						OVL_REDIRECT_FOLLOW :
+						OVL_REDIRECT_NOFOLLOW;
+			redirect_opt = true;
+			break;
+
+		case OPT_REDIRECT_DIR_FOLLOW:
+			config->redirect_mode = OVL_REDIRECT_FOLLOW;
+			redirect_opt = true;
+			break;
+
+		case OPT_REDIRECT_DIR_NOFOLLOW:
+			config->redirect_mode = OVL_REDIRECT_NOFOLLOW;
 			redirect_opt = true;
 			break;
 
@@ -654,22 +661,18 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config)
 		config->ovl_volatile = false;
 	}
 
-	err = ovl_parse_redirect_mode(config, config->redirect_mode);
-	if (err)
-		return err;
-
 	/*
 	 * This is to make the logic below simpler.  It doesn't make any other
-	 * difference, since config->redirect_dir is only used for upper.
+	 * difference, since redirect_dir=on is only used for upper.
 	 */
-	if (!config->upperdir && config->redirect_follow)
-		config->redirect_dir = true;
+	if (!config->upperdir && config->redirect_mode == OVL_REDIRECT_FOLLOW)
+		config->redirect_mode = OVL_REDIRECT_ON;
 
 	/* Resolve metacopy -> redirect_dir dependency */
-	if (config->metacopy && !config->redirect_dir) {
+	if (config->metacopy && config->redirect_mode != OVL_REDIRECT_ON) {
 		if (metacopy_opt && redirect_opt) {
 			pr_err("conflicting options: metacopy=on,redirect_dir=%s\n",
-			       config->redirect_mode);
+			       ovl_redirect_mode(config));
 			return -EINVAL;
 		}
 		if (redirect_opt) {
@@ -678,17 +681,18 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config)
 			 * in this conflict.
 			 */
 			pr_info("disabling metacopy due to redirect_dir=%s\n",
-				config->redirect_mode);
+				ovl_redirect_mode(config));
 			config->metacopy = false;
 		} else {
 			/* Automatically enable redirect otherwise. */
-			config->redirect_follow = config->redirect_dir = true;
+			config->redirect_mode = OVL_REDIRECT_ON;
 		}
 	}
 
 	/* Resolve nfs_export -> index dependency */
 	if (config->nfs_export && !config->index) {
-		if (!config->upperdir && config->redirect_follow) {
+		if (!config->upperdir &&
+		    config->redirect_mode != OVL_REDIRECT_NOFOLLOW) {
 			pr_info("NFS export requires \"redirect_dir=nofollow\" on non-upper mount, falling back to nfs_export=off.\n");
 			config->nfs_export = false;
 		} else if (nfs_export_opt && index_opt) {
@@ -733,9 +737,10 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config)
 
 	/* Resolve userxattr -> !redirect && !metacopy dependency */
 	if (config->userxattr) {
-		if (config->redirect_follow && redirect_opt) {
+		if (redirect_opt &&
+		    config->redirect_mode != OVL_REDIRECT_NOFOLLOW) {
 			pr_err("conflicting options: userxattr,redirect_dir=%s\n",
-			       config->redirect_mode);
+			       ovl_redirect_mode(config));
 			return -EINVAL;
 		}
 		if (config->metacopy && metacopy_opt) {
@@ -748,7 +753,7 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config)
 		 * options must be explicitly enabled if used together with
 		 * userxattr.
 		 */
-		config->redirect_dir = config->redirect_follow = false;
+		config->redirect_mode = OVL_REDIRECT_NOFOLLOW;
 		config->metacopy = false;
 	}
 
@@ -1332,10 +1337,17 @@ static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs,
 	if (err) {
 		pr_warn("failed to set xattr on upper\n");
 		ofs->noxattr = true;
-		if (ofs->config.index || ofs->config.metacopy) {
-			ofs->config.index = false;
+		if (ovl_redirect_follow(ofs)) {
+			ofs->config.redirect_mode = OVL_REDIRECT_NOFOLLOW;
+			pr_warn("...falling back to redirect_dir=nofollow.\n");
+		}
+		if (ofs->config.metacopy) {
 			ofs->config.metacopy = false;
-			pr_warn("...falling back to index=off,metacopy=off.\n");
+			pr_warn("...falling back to metacopy=off.\n");
+		}
+		if (ofs->config.index) {
+			ofs->config.index = false;
+			pr_warn("...falling back to index=off.\n");
 		}
 		/*
 		 * xattr support is required for persistent st_ino.
@@ -1963,6 +1975,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 	if (!cred)
 		goto out_err;
 
+	ofs->config.redirect_mode = ovl_redirect_mode_def();
 	ofs->config.index = ovl_index_def;
 	ofs->config.uuid = true;
 	ofs->config.nfs_export = ovl_nfs_export_def;