diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index f97ad8b40dbb..db22cbde1487 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -16,6 +16,8 @@
 #include <linux/posix_acl_xattr.h>
 #include <linux/exportfs.h>
 #include <linux/file.h>
+#include <linux/fs_context.h>
+#include <linux/fs_parser.h>
 #include "overlayfs.h"
 
 MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
@@ -67,6 +69,76 @@ 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 {
+	Opt_lowerdir,
+	Opt_upperdir,
+	Opt_workdir,
+	Opt_default_permissions,
+	Opt_redirect_dir,
+	Opt_index,
+	Opt_uuid,
+	Opt_nfs_export,
+	Opt_userxattr,
+	Opt_xino,
+	Opt_metacopy,
+	Opt_volatile,
+};
+
+static const struct constant_table ovl_parameter_bool[] = {
+	{ "on",		true  },
+	{ "off",	false },
+	{}
+};
+
+static const struct constant_table ovl_parameter_xino[] = {
+	{ "on",		OVL_XINO_ON   },
+	{ "off",	OVL_XINO_OFF  },
+	{ "auto",	OVL_XINO_AUTO },
+	{}
+};
+
+#define fsparam_string_empty(NAME, OPT) \
+	__fsparam(fs_param_is_string, NAME, OPT, fs_param_can_be_empty, NULL)
+
+static const struct fs_parameter_spec ovl_parameter_spec[] = {
+	fsparam_string_empty("lowerdir",    Opt_lowerdir),
+	fsparam_string_empty("upperdir",    Opt_upperdir),
+	fsparam_string_empty("workdir",     Opt_workdir),
+	fsparam_flag("default_permissions", Opt_default_permissions),
+	fsparam_enum("redirect_dir",        Opt_redirect_dir, ovl_parameter_xino),
+	fsparam_enum("index",               Opt_index, ovl_parameter_bool),
+	fsparam_enum("uuid",                Opt_uuid, ovl_parameter_bool),
+	fsparam_enum("nfs_export",          Opt_nfs_export, ovl_parameter_bool),
+	fsparam_flag("userxattr",           Opt_userxattr),
+	fsparam_enum("xino",                Opt_xino, ovl_parameter_bool),
+	fsparam_enum("metacopy",            Opt_metacopy, ovl_parameter_bool),
+	fsparam_flag("volatile",            Opt_volatile),
+	{}
+};
+
+struct ovl_fs_context_layer {
+	char *name;
+	struct path path;
+};
+
+/*
+ * These options imply different behavior when they are explicitly
+ * specified than when they are left in their default state.
+ */
+#define OVL_METACOPY_SET	BIT(0)
+#define OVL_REDIRECT_SET	BIT(1)
+#define OVL_NFS_EXPORT_SET	BIT(2)
+#define OVL_INDEX_SET		BIT(3)
+
+struct ovl_fs_context {
+	struct path upper;
+	struct path work;
+	size_t capacity;
+	size_t nr;
+	u8 set;
+	struct ovl_fs_context_layer *lower;
+};
+
 static void ovl_dentry_release(struct dentry *dentry)
 {
 	struct ovl_entry *oe = dentry->d_fsdata;
@@ -394,27 +466,6 @@ static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
 	return 0;
 }
 
-static int ovl_remount(struct super_block *sb, int *flags, char *data)
-{
-	struct ovl_fs *ofs = sb->s_fs_info;
-	struct super_block *upper_sb;
-	int ret = 0;
-
-	if (!(*flags & SB_RDONLY) && ovl_force_readonly(ofs))
-		return -EROFS;
-
-	if (*flags & SB_RDONLY && !sb_rdonly(sb)) {
-		upper_sb = ovl_upper_mnt(ofs)->mnt_sb;
-		if (ovl_should_sync(ofs)) {
-			down_read(&upper_sb->s_umount);
-			ret = sync_filesystem(upper_sb);
-			up_read(&upper_sb->s_umount);
-		}
-	}
-
-	return ret;
-}
-
 static const struct super_operations ovl_super_operations = {
 	.alloc_inode	= ovl_alloc_inode,
 	.free_inode	= ovl_free_inode,
@@ -424,76 +475,8 @@ static const struct super_operations ovl_super_operations = {
 	.sync_fs	= ovl_sync_fs,
 	.statfs		= ovl_statfs,
 	.show_options	= ovl_show_options,
-	.remount_fs	= ovl_remount,
-};
-
-enum {
-	OPT_LOWERDIR,
-	OPT_UPPERDIR,
-	OPT_WORKDIR,
-	OPT_DEFAULT_PERMISSIONS,
-	OPT_REDIRECT_DIR,
-	OPT_INDEX_ON,
-	OPT_INDEX_OFF,
-	OPT_UUID_ON,
-	OPT_UUID_OFF,
-	OPT_NFS_EXPORT_ON,
-	OPT_USERXATTR,
-	OPT_NFS_EXPORT_OFF,
-	OPT_XINO_ON,
-	OPT_XINO_OFF,
-	OPT_XINO_AUTO,
-	OPT_METACOPY_ON,
-	OPT_METACOPY_OFF,
-	OPT_VOLATILE,
-	OPT_ERR,
-};
-
-static const match_table_t ovl_tokens = {
-	{OPT_LOWERDIR,			"lowerdir=%s"},
-	{OPT_UPPERDIR,			"upperdir=%s"},
-	{OPT_WORKDIR,			"workdir=%s"},
-	{OPT_DEFAULT_PERMISSIONS,	"default_permissions"},
-	{OPT_REDIRECT_DIR,		"redirect_dir=%s"},
-	{OPT_INDEX_ON,			"index=on"},
-	{OPT_INDEX_OFF,			"index=off"},
-	{OPT_USERXATTR,			"userxattr"},
-	{OPT_UUID_ON,			"uuid=on"},
-	{OPT_UUID_OFF,			"uuid=off"},
-	{OPT_NFS_EXPORT_ON,		"nfs_export=on"},
-	{OPT_NFS_EXPORT_OFF,		"nfs_export=off"},
-	{OPT_XINO_ON,			"xino=on"},
-	{OPT_XINO_OFF,			"xino=off"},
-	{OPT_XINO_AUTO,			"xino=auto"},
-	{OPT_METACOPY_ON,		"metacopy=on"},
-	{OPT_METACOPY_OFF,		"metacopy=off"},
-	{OPT_VOLATILE,			"volatile"},
-	{OPT_ERR,			NULL}
 };
 
-static char *ovl_next_opt(char **s)
-{
-	char *sbegin = *s;
-	char *p;
-
-	if (sbegin == NULL)
-		return NULL;
-
-	for (p = sbegin; *p; p++) {
-		if (*p == '\\') {
-			p++;
-			if (!*p)
-				break;
-		} else if (*p == ',') {
-			*p = '\0';
-			*s = p + 1;
-			return sbegin;
-		}
-	}
-	*s = NULL;
-	return sbegin;
-}
-
 static int ovl_parse_redirect_mode(struct ovl_config *config, const char *mode)
 {
 	if (strcmp(mode, "on") == 0) {
@@ -517,123 +500,14 @@ static int ovl_parse_redirect_mode(struct ovl_config *config, const char *mode)
 	return 0;
 }
 
-static int ovl_parse_opt(char *opt, struct ovl_config *config)
+static int ovl_fs_params_verify(const struct ovl_fs_context *ctx,
+				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];
-
-		if (!*p)
-			continue;
-
-		token = match_token(p, ovl_tokens, args);
-		switch (token) {
-		case OPT_UPPERDIR:
-			kfree(config->upperdir);
-			config->upperdir = match_strdup(&args[0]);
-			if (!config->upperdir)
-				return -ENOMEM;
-			break;
-
-		case OPT_LOWERDIR:
-			kfree(config->lowerdir);
-			config->lowerdir = match_strdup(&args[0]);
-			if (!config->lowerdir)
-				return -ENOMEM;
-			break;
-
-		case OPT_WORKDIR:
-			kfree(config->workdir);
-			config->workdir = match_strdup(&args[0]);
-			if (!config->workdir)
-				return -ENOMEM;
-			break;
-
-		case OPT_DEFAULT_PERMISSIONS:
-			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;
-			redirect_opt = true;
-			break;
-
-		case OPT_INDEX_ON:
-			config->index = true;
-			index_opt = true;
-			break;
-
-		case OPT_INDEX_OFF:
-			config->index = false;
-			index_opt = true;
-			break;
-
-		case OPT_UUID_ON:
-			config->uuid = true;
-			break;
-
-		case OPT_UUID_OFF:
-			config->uuid = false;
-			break;
-
-		case OPT_NFS_EXPORT_ON:
-			config->nfs_export = true;
-			nfs_export_opt = true;
-			break;
-
-		case OPT_NFS_EXPORT_OFF:
-			config->nfs_export = false;
-			nfs_export_opt = true;
-			break;
-
-		case OPT_XINO_ON:
-			config->xino = OVL_XINO_ON;
-			break;
-
-		case OPT_XINO_OFF:
-			config->xino = OVL_XINO_OFF;
-			break;
-
-		case OPT_XINO_AUTO:
-			config->xino = OVL_XINO_AUTO;
-			break;
-
-		case OPT_METACOPY_ON:
-			config->metacopy = true;
-			metacopy_opt = true;
-			break;
-
-		case OPT_METACOPY_OFF:
-			config->metacopy = false;
-			metacopy_opt = true;
-			break;
-
-		case OPT_VOLATILE:
-			config->ovl_volatile = true;
-			break;
-
-		case OPT_USERXATTR:
-			config->userxattr = true;
-			break;
-
-		default:
-			pr_err("unrecognized mount option \"%s\" or missing value\n",
-					p);
-			return -EINVAL;
-		}
-	}
+	bool metacopy_opt = ctx->set & OVL_METACOPY_SET,
+	     redirect_opt = ctx->set & OVL_REDIRECT_SET;
+	bool nfs_export_opt = ctx->set & OVL_NFS_EXPORT_SET,
+	     index_opt = ctx->set & OVL_INDEX_SET;
 
 	/* Workdir/index are useless in non-upper mount */
 	if (!config->upperdir) {
@@ -932,10 +806,6 @@ static int ovl_lower_dir(const char *name, struct path *path,
 	int fh_type;
 	int err;
 
-	err = ovl_mount_dir_noesc(name, path);
-	if (err)
-		return err;
-
 	err = ovl_check_namelen(path, ofs, name);
 	if (err)
 		return err;
@@ -984,9 +854,9 @@ static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir)
 	return ok;
 }
 
-static unsigned int ovl_split_lowerdirs(char *str)
+static size_t ovl_parse_param_split_lowerdirs(char *str)
 {
-	unsigned int ctr = 1;
+	size_t ctr = 1;
 	char *s, *d;
 
 	for (s = d = str;; s++, d++) {
@@ -1104,15 +974,12 @@ static int ovl_report_in_use(struct ovl_fs *ofs, const char *name)
 }
 
 static int ovl_get_upper(struct super_block *sb, struct ovl_fs *ofs,
-			 struct ovl_layer *upper_layer, struct path *upperpath)
+			 struct ovl_layer *upper_layer,
+			 const struct path *upperpath)
 {
 	struct vfsmount *upper_mnt;
 	int err;
 
-	err = ovl_mount_dir(ofs->config.upperdir, upperpath);
-	if (err)
-		goto out;
-
 	/* Upperdir path should not be r/o */
 	if (__mnt_is_readonly(upperpath->mnt)) {
 		pr_err("upper fs is r/o, try multi-lower layers mount\n");
@@ -1399,46 +1266,37 @@ static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs,
 }
 
 static int ovl_get_workdir(struct super_block *sb, struct ovl_fs *ofs,
-			   const struct path *upperpath)
+			   const struct path *upperpath,
+			   const struct path *workpath)
 {
 	int err;
-	struct path workpath = { };
-
-	err = ovl_mount_dir(ofs->config.workdir, &workpath);
-	if (err)
-		goto out;
 
 	err = -EINVAL;
-	if (upperpath->mnt != workpath.mnt) {
+	if (upperpath->mnt != workpath->mnt) {
 		pr_err("workdir and upperdir must reside under the same mount\n");
-		goto out;
+		return err;
 	}
-	if (!ovl_workdir_ok(workpath.dentry, upperpath->dentry)) {
+	if (!ovl_workdir_ok(workpath->dentry, upperpath->dentry)) {
 		pr_err("workdir and upperdir must be separate subtrees\n");
-		goto out;
+		return err;
 	}
 
-	ofs->workbasedir = dget(workpath.dentry);
+	ofs->workbasedir = dget(workpath->dentry);
 
 	if (ovl_inuse_trylock(ofs->workbasedir)) {
 		ofs->workdir_locked = true;
 	} else {
 		err = ovl_report_in_use(ofs, "workdir");
 		if (err)
-			goto out;
+			return err;
 	}
 
 	err = ovl_setup_trap(sb, ofs->workbasedir, &ofs->workbasedir_trap,
 			     "workdir");
 	if (err)
-		goto out;
-
-	err = ovl_make_workdir(sb, ofs, &workpath);
-
-out:
-	path_put(&workpath);
+		return err;
 
-	return err;
+	return ovl_make_workdir(sb, ofs, workpath);
 }
 
 static int ovl_get_indexdir(struct super_block *sb, struct ovl_fs *ofs,
@@ -1592,14 +1450,13 @@ static int ovl_get_fsid(struct ovl_fs *ofs, const struct path *path)
 }
 
 static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs,
-			  struct path *stack, unsigned int numlower,
-			  struct ovl_layer *layers)
+			  struct ovl_fs_context *ctx, struct ovl_layer *layers)
 {
 	int err;
 	unsigned int i;
 
 	err = -ENOMEM;
-	ofs->fs = kcalloc(numlower + 1, sizeof(struct ovl_sb), GFP_KERNEL);
+	ofs->fs = kcalloc(ctx->nr + 1, sizeof(struct ovl_sb), GFP_KERNEL);
 	if (ofs->fs == NULL)
 		goto out;
 
@@ -1623,12 +1480,13 @@ static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs,
 		ofs->fs[0].is_lower = false;
 	}
 
-	for (i = 0; i < numlower; i++) {
+	for (i = 0; i < ctx->nr; i++) {
+		struct ovl_fs_context_layer *l = &ctx->lower[i];
 		struct vfsmount *mnt;
 		struct inode *trap;
 		int fsid;
 
-		err = fsid = ovl_get_fsid(ofs, &stack[i]);
+		err = fsid = ovl_get_fsid(ofs, &l->path);
 		if (err < 0)
 			goto out;
 
@@ -1639,11 +1497,11 @@ static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs,
 		 * the upperdir/workdir is in fact in-use by our
 		 * upperdir/workdir.
 		 */
-		err = ovl_setup_trap(sb, stack[i].dentry, &trap, "lowerdir");
+		err = ovl_setup_trap(sb, l->path.dentry, &trap, "lowerdir");
 		if (err)
 			goto out;
 
-		if (ovl_is_inuse(stack[i].dentry)) {
+		if (ovl_is_inuse(l->path.dentry)) {
 			err = ovl_report_in_use(ofs, "lowerdir");
 			if (err) {
 				iput(trap);
@@ -1651,7 +1509,7 @@ static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs,
 			}
 		}
 
-		mnt = clone_private_mount(&stack[i]);
+		mnt = clone_private_mount(&l->path);
 		err = PTR_ERR(mnt);
 		if (IS_ERR(mnt)) {
 			pr_err("failed to clone lowerpath\n");
@@ -1712,63 +1570,86 @@ static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs,
 }
 
 static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb,
-				const char *lower, unsigned int numlower,
-				struct ovl_fs *ofs, struct ovl_layer *layers)
+					    struct ovl_fs_context *ctx,
+					    struct ovl_fs *ofs,
+					    struct ovl_layer *layers)
 {
 	int err;
-	struct path *stack = NULL;
 	unsigned int i;
 	struct ovl_entry *oe;
+	size_t len;
+	char *lowerdir;
+	struct ovl_fs_context_layer *l;
 
-	if (!ofs->config.upperdir && numlower == 1) {
+	if (!ofs->config.upperdir && ctx->nr == 1) {
 		pr_err("at least 2 lowerdir are needed while upperdir nonexistent\n");
 		return ERR_PTR(-EINVAL);
 	}
 
-	stack = kcalloc(numlower, sizeof(struct path), GFP_KERNEL);
-	if (!stack)
-		return ERR_PTR(-ENOMEM);
-
 	err = -EINVAL;
-	for (i = 0; i < numlower; i++) {
-		err = ovl_lower_dir(lower, &stack[i], ofs, &sb->s_stack_depth);
+	len = 0;
+	for (i = 0; i < ctx->nr; i++) {
+		l = &ctx->lower[i];
+
+		err = ovl_lower_dir(l->name, &l->path, ofs, &sb->s_stack_depth);
 		if (err)
-			goto out_err;
+			return ERR_PTR(err);
 
-		lower = strchr(lower, '\0') + 1;
+		len += strlen(l->name);
 	}
 
 	err = -EINVAL;
 	sb->s_stack_depth++;
 	if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
 		pr_err("maximum fs stacking depth exceeded\n");
-		goto out_err;
+		return ERR_PTR(err);
+	}
+
+	/*
+	 * Create a string of all lower layers that we store in
+	 * ofs->config.lowerdir which we can display to userspace in
+	 * mount options. For example, this assembles "/lower1",
+	 * "/lower2" into "/lower1:/lower2".
+	 *
+	 * We need to make sure we add a ':'. Thus, we need to account
+	 * for the separators when allocating space when multiple layers
+	 * are specified. That should be easy since we know that ctx->nr
+	 * >= 1. So we know that ctx->nr - 1 will be correct for the
+	 * base case ctx->nr == 1 and all other cases.
+	 */
+	len += ctx->nr - 1;
+	len++; /* and leave room for \0 */
+	lowerdir = kzalloc(len, GFP_KERNEL_ACCOUNT);
+	if (!lowerdir)
+		return ERR_PTR(-ENOMEM);
+
+	ofs->config.lowerdir = lowerdir;
+	for (i = 0; i < ctx->nr; i++) {
+		l = &ctx->lower[i];
+
+		len = strlen(l->name);
+		memcpy(lowerdir, l->name, len);
+		if ((ctx->nr > 1) && ((i + 1) != ctx->nr))
+			lowerdir[len++] = ':';
+		lowerdir += len;
 	}
 
-	err = ovl_get_layers(sb, ofs, stack, numlower, layers);
+	err = ovl_get_layers(sb, ofs, ctx, layers);
 	if (err)
-		goto out_err;
+		return ERR_PTR(err);
 
 	err = -ENOMEM;
-	oe = ovl_alloc_entry(numlower);
+	oe = ovl_alloc_entry(ctx->nr);
 	if (!oe)
-		goto out_err;
+		return ERR_PTR(err);
 
-	for (i = 0; i < numlower; i++) {
-		oe->lowerstack[i].dentry = dget(stack[i].dentry);
-		oe->lowerstack[i].layer = &ofs->layers[i+1];
+	for (i = 0; i < ctx->nr; i++) {
+		l = &ctx->lower[i];
+		oe->lowerstack[i].dentry = dget(l->path.dentry);
+		oe->lowerstack[i].layer = &ofs->layers[i + 1];
 	}
 
-out:
-	for (i = 0; i < numlower; i++)
-		path_put(&stack[i]);
-	kfree(stack);
-
 	return oe;
-
-out_err:
-	oe = ERR_PTR(err);
-	goto out;
 }
 
 /*
@@ -1878,72 +1759,354 @@ static struct dentry *ovl_get_root(struct super_block *sb,
 	ovl_set_upperdata(d_inode(root));
 	ovl_inode_init(d_inode(root), &oip, ino, fsid);
 	ovl_dentry_update_reval(root, upperdentry, DCACHE_OP_WEAK_REVALIDATE);
+	/*
+	 * We're going to put upper path when we call
+	 * fs_context_operations->free() take an additional
+	 * reference so we can just call path_put().
+	 */
+	dget(upperdentry);
 
 	return root;
 }
 
-static int ovl_fill_super(struct super_block *sb, void *data, int silent)
+static inline void ovl_parse_param_drop_lowerdir(struct ovl_fs_context *ctx)
+{
+	for (size_t nr = 0; nr < ctx->nr; nr++) {
+		path_put(&ctx->lower[nr].path);
+		kfree(ctx->lower[nr].name);
+		ctx->lower[nr].name = NULL;
+	}
+	ctx->nr = 0;
+}
+
+/*
+ * Parse lowerdir= mount option:
+ *
+ * (1) lowerdir=/lower1:/lower2:/lower3
+ *     Set "/lower1", "/lower2", and "/lower3" as lower layers. Any
+ *     existing lower layers are replaced.
+ * (2) lowerdir=:/lower4
+ *     Append "/lower4" to current stack of lower layers. This requires
+ *     that there already is at least one lower layer configured.
+ */
+static int ovl_parse_param_lowerdir(const char *name, struct fs_context *fc)
+{
+	int err;
+	struct ovl_fs_context *ctx = fc->fs_private;
+	struct ovl_fs_context_layer *l;
+	char *dup = NULL, *dup_iter;
+	size_t nr_lower = 0, nr = 0;
+	bool append = false;
+
+	/* Enforce that users are forced to specify a single ':'. */
+	if (strncmp(name, "::", 2) == 0)
+		return -EINVAL;
+
+	/*
+	 * Ensure we're backwards compatible with mount(2)
+	 * by allowing relative paths.
+	 */
+
+	/* drop all existing lower layers */
+	if (!*name) {
+		ovl_parse_param_drop_lowerdir(ctx);
+		return 0;
+	}
+
+	if (*name == ':') {
+		/*
+		 * If users want to append a layer enforce that they
+		 * have already specified a first layer before. It's
+		 * better to be strict.
+		 */
+		if (ctx->nr == 0)
+			return -EINVAL;
+
+		/*
+		 * Drop the leading. We'll create the final mount option
+		 * string for the lower layers when we create the superblock.
+		 */
+		name++;
+		append = true;
+	}
+
+	dup = kstrdup(name, GFP_KERNEL);
+	if (!dup)
+		return -ENOMEM;
+
+	err = -EINVAL;
+	nr_lower = ovl_parse_param_split_lowerdirs(dup);
+	if ((nr_lower > OVL_MAX_STACK) ||
+	    (append && (size_add(ctx->nr, nr_lower) > OVL_MAX_STACK))) {
+		pr_err("too many lower directories, limit is %d\n", OVL_MAX_STACK);
+		goto out_err;
+	}
+
+	if (!append)
+		ovl_parse_param_drop_lowerdir(ctx);
+
+	/*
+	 * (1) append
+	 *
+	 * We want nr <= nr_lower <= capacity We know nr > 0 and nr <=
+	 * capacity. If nr == 0 this wouldn't be append. If nr +
+	 * nr_lower is <= capacity then nr <= nr_lower <= capacity
+	 * already holds. If nr + nr_lower exceeds capacity, we realloc.
+	 *
+	 * (2) replace
+	 *
+	 * Ensure we're backwards compatible with mount(2) which allows
+	 * "lowerdir=/a:/b:/c,lowerdir=/d:/e:/f" causing the last
+	 * specified lowerdir mount option to win.
+	 *
+	 * We want nr <= nr_lower <= capacity We know either (i) nr == 0
+	 * or (ii) nr > 0. We also know nr_lower > 0. The capacity
+	 * could've been changed multiple times already so we only know
+	 * nr <= capacity. If nr + nr_lower > capacity we realloc,
+	 * otherwise nr <= nr_lower <= capacity holds already.
+	 */
+	nr_lower += ctx->nr;
+	if (nr_lower > ctx->capacity) {
+		err = -ENOMEM;
+		l = krealloc_array(ctx->lower, nr_lower, sizeof(*ctx->lower),
+				   GFP_KERNEL_ACCOUNT);
+		if (!l)
+			goto out_err;
+
+		ctx->lower = l;
+		ctx->capacity = nr_lower;
+	}
+
+	/* By (1) and (2) we know nr <= nr_lower <= capacity. */
+	dup_iter = dup;
+	for (nr = ctx->nr; nr < nr_lower; nr++) {
+		l = &ctx->lower[nr];
+
+		err = ovl_mount_dir_noesc(dup_iter, &l->path);
+		if (err)
+			goto out_put;
+
+		err = -ENOMEM;
+		l->name = kstrdup(dup_iter, GFP_KERNEL_ACCOUNT);
+		if (!l->name)
+			goto out_put;
+
+		dup_iter = strchr(dup_iter, '\0') + 1;
+	}
+	ctx->nr = nr_lower;
+	kfree(dup);
+	return 0;
+
+out_put:
+	/*
+	 * We know nr >= ctx->nr < nr_lower. If we failed somewhere
+	 * we want to undo until nr == ctx->nr. This is correct for
+	 * both ctx->nr == 0 and ctx->nr > 0.
+	 */
+	for (; nr >= ctx->nr; nr--) {
+		l = &ctx->lower[nr];
+		kfree(l->name);
+		l->name = NULL;
+		path_put(&l->path);
+
+		/* don't overflow */
+		if (nr == 0)
+			break;
+	}
+
+out_err:
+	kfree(dup);
+
+	/* Intentionally don't realloc to a smaller size. */
+	return err;
+}
+
+static int ovl_parse_param(struct fs_context *fc, struct fs_parameter *param)
+{
+	int err = 0;
+	struct fs_parse_result result;
+	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;
+	int opt;
+	char *sval;
+
+	/*
+	 * On remount overlayfs has always ignored all mount options no
+	 * matter if malformed or not so for backwards compatibility we
+	 * do the same here.
+	 */
+	if (fc->purpose == FS_CONTEXT_FOR_RECONFIGURE)
+		return 0;
+
+	opt = fs_parse(fc, ovl_parameter_spec, param, &result);
+	if (opt < 0)
+		return opt;
+
+	switch (opt) {
+	case Opt_lowerdir:
+		err = ovl_parse_param_lowerdir(param->string, fc);
+		break;
+	case Opt_upperdir:
+		err = ovl_mount_dir(param->string, &path);
+		if (err)
+			break;
+
+		/*
+		 * 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);
+			err = -EINVAL;
+			break;
+		}
+
+		dup = kstrdup(param->string, GFP_KERNEL);
+		if (!dup) {
+			path_put(&path);
+			err = -ENOMEM;
+			break;
+		}
+
+		kfree(config->upperdir);
+		config->upperdir = dup;
+		path_put(&ctx->upper);
+		ctx->upper = path;
+		break;
+	case Opt_workdir:
+		err = ovl_mount_dir(param->string, &path);
+		if (err)
+			break;
+		dup = kstrdup(param->string, GFP_KERNEL);
+		if (!dup) {
+			path_put(&path);
+			err = -ENOMEM;
+			break;
+		}
+
+		kfree(config->workdir);
+		config->workdir = dup;
+		path_put(&ctx->work);
+		ctx->work = path;
+		break;
+	case Opt_default_permissions:
+		config->default_permissions = true;
+		break;
+	case Opt_index:
+		config->index = result.uint_32;
+		ctx->set |= OVL_INDEX_SET;
+		break;
+	case Opt_uuid:
+		config->uuid = result.uint_32;
+		break;
+	case Opt_nfs_export:
+		config->nfs_export = result.uint_32;
+		ctx->set |= OVL_NFS_EXPORT_SET;
+		break;
+	case Opt_metacopy:
+		config->metacopy = result.uint_32;
+		ctx->set |= OVL_METACOPY_SET;
+		break;
+	case Opt_userxattr:
+		config->userxattr = true;
+		break;
+	case Opt_volatile:
+		config->ovl_volatile = true;
+		break;
+	case Opt_xino:
+		config->xino = result.uint_32;
+		break;
+	case Opt_redirect_dir:
+		if (result.uint_32 == true)
+			sval = kstrdup("on", GFP_KERNEL);
+		else
+			sval = kstrdup("off", GFP_KERNEL);
+		if (!sval) {
+			err = -ENOMEM;
+			break;
+		}
+
+		kfree(config->redirect_mode);
+		config->redirect_mode = sval;
+		ctx->set |= OVL_REDIRECT_SET;
+		break;
+	default:
+		pr_err("unrecognized mount option \"%s\" or missing value\n", param->key);
+		return -EINVAL;
+	}
+
+	return err;
+}
+
+
+static int ovl_reconfigure(struct fs_context *fc)
+{
+	struct super_block *sb = fc->root->d_sb;
+	struct ovl_fs *ofs = sb->s_fs_info;
+	struct super_block *upper_sb;
+	int ret = 0;
+
+	if (!(fc->sb_flags & SB_RDONLY) && ovl_force_readonly(ofs))
+		return -EROFS;
+
+	if (fc->sb_flags & SB_RDONLY && !sb_rdonly(sb)) {
+		upper_sb = ovl_upper_mnt(ofs)->mnt_sb;
+		if (ovl_should_sync(ofs)) {
+			down_read(&upper_sb->s_umount);
+			ret = sync_filesystem(upper_sb);
+			up_read(&upper_sb->s_umount);
+		}
+	}
+
+	return ret;
+}
+
+static int ovl_fill_super(struct super_block *sb, struct fs_context *fc)
 {
-	struct path upperpath = { };
+	struct ovl_fs *ofs = sb->s_fs_info;
+	struct ovl_fs_context *ctx = fc->fs_private;
+
 	struct dentry *root_dentry;
 	struct ovl_entry *oe;
-	struct ovl_fs *ofs;
 	struct ovl_layer *layers;
 	struct cred *cred;
-	char *splitlower = NULL;
-	unsigned int numlower;
 	int err;
 
 	err = -EIO;
-	if (WARN_ON(sb->s_user_ns != current_user_ns()))
-		goto out;
+	if (WARN_ON(fc->user_ns != current_user_ns()))
+		goto out_err;
 
+	ofs->share_whiteout = true;
 	sb->s_d_op = &ovl_dentry_operations;
 
-	err = -ENOMEM;
-	ofs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL);
-	if (!ofs)
-		goto out;
-
 	err = -ENOMEM;
 	ofs->creator_cred = cred = prepare_creds();
 	if (!cred)
 		goto out_err;
 
-	/* Is there a reason anyone would want not to share whiteouts? */
-	ofs->share_whiteout = true;
-
-	ofs->config.index = ovl_index_def;
-	ofs->config.uuid = true;
-	ofs->config.nfs_export = ovl_nfs_export_def;
-	ofs->config.xino = ovl_xino_def();
-	ofs->config.metacopy = ovl_metacopy_def;
-	err = ovl_parse_opt((char *) data, &ofs->config);
+	err = ovl_fs_params_verify(ctx, &ofs->config);
 	if (err)
 		goto out_err;
 
+	/*
+	 * Check ctx->nr instead of ofs->config.lowerdir since we're
+	 * going to set ofs->config.lowerdir here after we know that the
+	 * user specified all layers.
+	 */
 	err = -EINVAL;
-	if (!ofs->config.lowerdir) {
-		if (!silent)
+	if (ctx->nr == 0) {
+		if (fc->sb_flags & SB_SILENT)
 			pr_err("missing 'lowerdir'\n");
 		goto out_err;
 	}
 
 	err = -ENOMEM;
-	splitlower = kstrdup(ofs->config.lowerdir, GFP_KERNEL);
-	if (!splitlower)
-		goto out_err;
-
-	err = -EINVAL;
-	numlower = ovl_split_lowerdirs(splitlower);
-	if (numlower > OVL_MAX_STACK) {
-		pr_err("too many lower directories, limit is %d\n",
-		       OVL_MAX_STACK);
-		goto out_err;
-	}
-
-	err = -ENOMEM;
-	layers = kcalloc(numlower + 1, sizeof(struct ovl_layer), GFP_KERNEL);
+	layers = kcalloc(ctx->nr + 1, sizeof(struct ovl_layer), GFP_KERNEL);
 	if (!layers)
 		goto out_err;
 
@@ -1975,7 +2138,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 			goto out_err;
 		}
 
-		err = ovl_get_upper(sb, ofs, &layers[0], &upperpath);
+		err = ovl_get_upper(sb, ofs, &layers[0], &ctx->upper);
 		if (err)
 			goto out_err;
 
@@ -1989,7 +2152,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 			}
 		}
 
-		err = ovl_get_workdir(sb, ofs, &upperpath);
+		err = ovl_get_workdir(sb, ofs, &ctx->upper, &ctx->work);
 		if (err)
 			goto out_err;
 
@@ -1999,7 +2162,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 		sb->s_stack_depth = upper_sb->s_stack_depth;
 		sb->s_time_gran = upper_sb->s_time_gran;
 	}
-	oe = ovl_get_lowerstack(sb, splitlower, numlower, ofs, layers);
+	oe = ovl_get_lowerstack(sb, ctx, ofs, layers);
 	err = PTR_ERR(oe);
 	if (IS_ERR(oe))
 		goto out_err;
@@ -2014,7 +2177,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 	}
 
 	if (!ovl_force_readonly(ofs) && ofs->config.index) {
-		err = ovl_get_indexdir(sb, ofs, oe, &upperpath);
+		err = ovl_get_indexdir(sb, ofs, oe, &ctx->upper);
 		if (err)
 			goto out_free_oe;
 
@@ -2055,13 +2218,10 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 	sb->s_iflags |= SB_I_SKIP_SYNC;
 
 	err = -ENOMEM;
-	root_dentry = ovl_get_root(sb, upperpath.dentry, oe);
+	root_dentry = ovl_get_root(sb, ctx->upper.dentry, oe);
 	if (!root_dentry)
 		goto out_free_oe;
 
-	mntput(upperpath.mnt);
-	kfree(splitlower);
-
 	sb->s_root = root_dentry;
 
 	return 0;
@@ -2070,25 +2230,105 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 	ovl_entry_stack_free(oe);
 	kfree(oe);
 out_err:
-	kfree(splitlower);
-	path_put(&upperpath);
-	ovl_free_fs(ofs);
-out:
 	return err;
 }
 
-static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags,
-				const char *dev_name, void *raw_data)
+static int ovl_get_tree(struct fs_context *fc)
+{
+	return get_tree_nodev(fc, ovl_fill_super);
+}
+
+static inline void ovl_fs_context_free(struct ovl_fs_context *ctx)
+{
+	ovl_parse_param_drop_lowerdir(ctx);
+	path_put(&ctx->upper);
+	path_put(&ctx->work);
+	kfree(ctx->lower);
+	kfree(ctx);
+}
+
+static void ovl_free(struct fs_context *fc)
 {
-	return mount_nodev(fs_type, flags, raw_data, ovl_fill_super);
+	struct ovl_fs *ofs = fc->s_fs_info;
+	struct ovl_fs_context *ctx = fc->fs_private;
+
+	/*
+	 * ofs is stored in the fs_context when it is initialized.
+	 * ofs is transferred to the superblock on a successful mount,
+	 * but if an error occurs before the transfer we have to free
+	 * it here.
+	 */
+	if (ofs)
+		ovl_free_fs(ofs);
+
+	if (ctx)
+		ovl_fs_context_free(ctx);
+}
+
+static const struct fs_context_operations ovl_context_ops = {
+	.parse_param = ovl_parse_param,
+	.get_tree    = ovl_get_tree,
+	.reconfigure = ovl_reconfigure,
+	.free        = ovl_free,
+};
+
+/*
+ * This is called during fsopen() and will record the user namespace of
+ * the caller in fc->user_ns since we've raised FS_USERNS_MOUNT. We'll
+ * need it when we actually create the superblock to verify that the
+ * process creating the superblock is in the same user namespace as
+ * process that called fsopen().
+ */
+static int ovl_init_fs_context(struct fs_context *fc)
+{
+	struct ovl_fs_context *ctx = NULL;
+	struct ovl_fs *ofs = NULL;
+
+	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL_ACCOUNT);
+	if (!ctx)
+		goto out_err;
+
+	/*
+	 * By default we allocate for three lower layers. It's likely
+	 * that it'll cover most users.
+	 */
+	ctx->lower = kmalloc_array(3, sizeof(*ctx->lower), GFP_KERNEL_ACCOUNT);
+	if (!ctx->lower)
+		goto out_err;
+	ctx->capacity = 3;
+
+	ofs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL);
+	if (!ofs)
+		goto out_err;
+
+	ofs->config.redirect_mode = kstrdup(ovl_redirect_mode_def(), GFP_KERNEL);
+	if (!ofs->config.redirect_mode)
+		goto out_err;
+
+	ofs->config.index	= ovl_index_def;
+	ofs->config.uuid	= true;
+	ofs->config.nfs_export	= ovl_nfs_export_def;
+	ofs->config.xino	= ovl_xino_def();
+	ofs->config.metacopy	= ovl_metacopy_def;
+
+	fc->s_fs_info		= ofs;
+	fc->fs_private		= ctx;
+	fc->ops			= &ovl_context_ops;
+	return 0;
+
+out_err:
+	ovl_fs_context_free(ctx);
+	ovl_free_fs(ofs);
+	return -ENOMEM;
 }
 
 static struct file_system_type ovl_fs_type = {
-	.owner		= THIS_MODULE,
-	.name		= "overlay",
-	.fs_flags	= FS_USERNS_MOUNT,
-	.mount		= ovl_mount,
-	.kill_sb	= kill_anon_super,
+	.owner			= THIS_MODULE,
+	.name			= "overlay",
+	.init_fs_context	= ovl_init_fs_context,
+	.parameters		= ovl_parameter_spec,
+	.fs_flags		= FS_USERNS_MOUNT,
+	.kill_sb		= kill_anon_super,
 };
 MODULE_ALIAS_FS("overlay");
 
