diff --git a/fs/Kconfig b/fs/Kconfig
index ac474a61be37..25700b152c75 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -8,6 +8,13 @@ menu "File systems"
 config DCACHE_WORD_ACCESS
        bool
 
+config VALIDATE_FS_PARSER
+	bool "Validate filesystem parameter description"
+	default y
+	help
+	  Enable this to perform validation of the parameter description for a
+	  filesystem when it is registered.
+
 if BLOCK
 
 config FS_IOMAP
diff --git a/fs/Makefile b/fs/Makefile
index 293733f61594..07b894227dce 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -12,7 +12,8 @@ obj-y :=	open.o read_write.o file_table.o super.o \
 		attr.o bad_inode.o file.o filesystems.o namespace.o \
 		seq_file.o xattr.o libfs.o fs-writeback.o \
 		pnode.o splice.o sync.o utimes.o d_path.o \
-		stack.o fs_struct.o statfs.o fs_pin.o nsfs.o
+		stack.o fs_struct.o statfs.o fs_pin.o nsfs.o \
+		fs_parser.o
 
 ifeq ($(CONFIG_BLOCK),y)
 obj-y +=	buffer.o block_dev.o direct-io.o mpage.o
diff --git a/fs/fs_parser.c b/fs/fs_parser.c
new file mode 100644
index 000000000000..12401b38cd51
--- /dev/null
+++ b/fs/fs_parser.c
@@ -0,0 +1,476 @@
+/* Filesystem parameter parser.
+ *
+ * Copyright (C) 2018 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#include <linux/export.h>
+#include <linux/fs_context.h>
+#include <linux/fs_parser.h>
+#include <linux/slab.h>
+#include <linux/security.h>
+#include <linux/namei.h>
+#include <linux/bsearch.h>
+#include "internal.h"
+
+static const struct constant_table bool_names[] = {
+	{ "0",		false },
+	{ "1",		true },
+	{ "false",	false },
+	{ "no",		false },
+	{ "true",	true },
+	{ "yes",	true },
+};
+
+static int cmp_constant(const void *name, const void *entry)
+{
+	const struct constant_table *e = entry;
+	return strcmp(name, e->name);
+}
+
+/**
+ * lookup_constant - Look up a constant by name in an ordered table
+ * @tbl: The table of constants to search.
+ * @tbl_size: The size of the table.
+ * @name: The name to look up.
+ * @not_found: The value to return if the name is not found.
+ */
+int __lookup_constant(const struct constant_table *tbl, size_t tbl_size,
+		      const char *name, int not_found)
+{
+	const struct constant_table *e;
+
+	e = bsearch(name, tbl, tbl_size, sizeof(tbl[0]), cmp_constant);
+	if (!e)
+		return not_found;
+	return e->value;
+}
+EXPORT_SYMBOL(__lookup_constant);
+
+/*
+ * fs_parse - Parse a filesystem configuration parameter
+ * @fc: The filesystem context to log errors through.
+ * @desc: The parameter description to use.
+ * @param: The parameter.
+ * @result: Where to place the result of the parse
+ *
+ * Parse a filesystem configuration parameter and attempt a conversion for a
+ * simple parameter for which this is requested.  If successful, the determined
+ * parameter ID is placed into @result->key, the desired type is indicated in
+ * @result->t and any converted value is placed into an appropriate member of
+ * the union in @result.
+ *
+ * The function returns 1 if the parameter was matched, 0 if it wasn't matched
+ * and @desc->ignore_unknown indicated that unknown parameters are okay and
+ * -EINVAL if there was a conversion issue or the parameter wasn't recognised
+ * and unknowns aren't okay.
+ */
+int fs_parse(struct fs_context *fc,
+	     const struct fs_parameter_description *desc,
+	     struct fs_parameter *param,
+	     struct fs_parse_result *result)
+{
+	int ret, k, i, b;
+
+	k = __lookup_constant(desc->keys, desc->nr_keys, param->key,
+			      -EAGAIN);
+	if (k == -EAGAIN) {
+		/* If we didn't find something that looks like "noxxx", see if
+		 * "xxx" takes the "no"-form negative - but only if there
+		 * wasn't an value.
+		 */
+		if (param->string || param->size > 0)
+			goto unknown_parameter;
+		if (param->key[0] != 'n' || param->key[1] != 'o' || !param->key[2])
+			goto unknown_parameter;
+
+		k = __lookup_constant(desc->keys, desc->nr_keys,
+				      param->key + 2, -EAGAIN);
+		if (k == -EAGAIN)
+			goto unknown_parameter;
+		if (!(desc->specs[k].flags & fs_param_neg_with_no))
+			goto unknown_parameter;
+		result->key = k;
+		result->uint_32 = 0;
+		result->negated = true;
+		goto okay;
+	}
+
+	result->key = k;
+	result->negated = false;
+	if (result->key == fsconfig_key_removed)
+		return invalf(fc, "%s: Unsupported parameter name '%s'",
+			      desc->name, param->key);
+
+	result->t = desc->specs[result->key];
+	if (result->t.flags & fs_param_deprecated)
+		warnf(fc, "%s: Deprecated parameter '%s'",
+		      desc->name, param->key);
+
+	/* Certain parameter types only take a string and convert it. */
+	switch (result->t.type) {
+	case __fs_param_wasnt_defined:
+		return -EINVAL;
+	case fs_param_is_u32:
+	case fs_param_is_u32_octal:
+	case fs_param_is_u32_hex:
+	case fs_param_is_s32:
+	case fs_param_is_enum:
+	case fs_param_is_string:
+		if (param->type != fs_value_is_string)
+			goto bad_value;
+		/* Fall through */
+	default:
+		break;
+	}
+
+	/* Try to turn the type we were given into the type desired by the
+	 * parameter and give an error if we can't.
+	 */
+	switch (result->t.type) {
+	case fs_param_takes_no_value:
+		if (param->type != fs_value_is_flag &&
+		    (param->type != fs_value_is_string || param->size > 0))
+			return invalf(fc, "%s: Unexpected value for '%s'",
+				      desc->name, param->key);
+		result->boolean = true;
+		goto okay;
+
+	case fs_param_is_bool:
+		switch (param->type) {
+		case fs_value_is_flag:
+			result->boolean = true;
+			goto okay;
+		case fs_value_is_string:
+			if (param->size == 0) {
+				result->boolean = true;
+				goto okay;
+			}
+			b = lookup_constant(bool_names, param->string, -1);
+			if (b == -1)
+				goto bad_value;
+			result->boolean = b;
+			goto okay;
+		default:
+			goto bad_value;
+		}
+
+	case fs_param_is_u32:
+		ret = kstrtouint(param->string, 0, &result->uint_32);
+		goto maybe_okay;
+	case fs_param_is_u32_octal:
+		ret = kstrtouint(param->string, 8, &result->uint_32);
+		goto maybe_okay;
+	case fs_param_is_u32_hex:
+		ret = kstrtouint(param->string, 16, &result->uint_32);
+		goto maybe_okay;
+	case fs_param_is_s32:
+		ret = kstrtoint(param->string, 0, &result->int_32);
+		goto maybe_okay;
+
+	case fs_param_is_enum:
+		for (i = 0; i < desc->nr_enums; i++) {
+			if (desc->enums[i].param_id == result->key &&
+			    strcmp(desc->enums[i].name, param->string) == 0) {
+				result->uint_32 = desc->enums[i].value;
+				goto okay;
+			}
+		}
+		goto bad_value;
+
+	case fs_param_is_string:
+		goto okay;
+	case fs_param_is_blob:
+		if (param->type != fs_value_is_blob)
+			goto bad_value;
+		goto okay;
+
+	case fs_param_is_fd: {
+		if (param->type != fs_value_is_file)
+			goto bad_value;
+		goto okay;
+	}
+
+	case fs_param_is_blockdev:
+	case fs_param_is_path:
+		goto okay;
+	default:
+		BUG();
+	}
+
+maybe_okay:
+	if (ret < 0)
+		goto bad_value;
+okay:
+	return 1;
+
+bad_value:
+	return invalf(fc, "%s: Bad value for '%s'", desc->name, param->key);
+unknown_parameter:
+	if (desc->ignore_unknown)
+		return 0;
+	if (desc->no_source && strcmp(param->key, "source") == 0)
+		return 0; /* The source parameter is special */
+	return invalf(fc, "%s: Unknown parameter '%s'", desc->name, param->key);
+}
+EXPORT_SYMBOL(fs_parse);
+
+/**
+ * fs_lookup_param - Look up a path referred to by a parameter
+ * @fc: The filesystem context to log errors through.
+ * @desc: The parameter description that was used
+ * @key: The name of the parameter.
+ * @value: The supplied value for the parameter
+ * @result: The result of the parse from a previous call to fs_parse()
+ * @_path: The result of the lookup
+ */
+int fs_lookup_param(struct fs_context *fc,
+		    const struct fs_parameter_description *desc,
+		    struct fs_parameter *param,
+		    struct fs_parse_result *result,
+		    struct path *_path)
+{
+	struct filename *f;
+	unsigned int flags = 0;
+	bool put_f;
+	int ret;
+
+	switch (param->type) {
+	case fs_value_is_string:
+		f = getname_kernel(param->string);
+		if (IS_ERR(f))
+			return PTR_ERR(f);
+		put_f = true;
+		break;
+	case fs_value_is_filename_empty:
+		flags = LOOKUP_EMPTY;
+		/* Fall through */
+	case fs_value_is_filename:
+		f = param->name;
+		put_f = false;
+		break;
+	default:
+		return invalf(fc, "%s: '%s' not usable as path",
+			      desc->name, param->key);
+	}
+
+	ret = filename_lookup(param->dirfd, f, flags, _path, NULL);
+	if (put_f)
+		putname(f);
+	if (ret < 0) {
+		errorf(fc, "%s: Lookup failure for '%s'",
+		       desc->name, param->key);
+		return ret;
+	}
+
+	if (result->t.type == fs_param_is_blockdev &&
+	    !S_ISBLK(d_real_inode(_path->dentry)->i_mode)) {
+		path_put(_path);
+		_path->dentry = NULL;
+		_path->mnt = NULL;
+		errorf(fc, "%s: Non-blockdev passed to '%s'",
+		       desc->name, param->key);
+		return -ENOTBLK;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(fs_lookup_param);
+
+#ifdef CONFIG_VALIDATE_FS_PARSER
+/**
+ * validate_constant_table - Validate a constant table
+ * @tbl: The constant table to validate.
+ * @tbl_size: The size of the table.
+ * @low: The lowest permissible value.
+ * @high: The highest permissible value.
+ * @special: One special permissible value outside of the range.
+ */
+bool validate_constant_table(const struct constant_table *tbl, size_t tbl_size,
+			     int low, int high, int special)
+{
+	size_t i;
+	bool good = true;
+
+	if (tbl_size == 0) {
+		pr_warn("VALIDATE C-TBL: Empty\n");
+		return true;
+	}
+
+	for (i = 0; i < tbl_size; i++) {
+		if (!tbl[i].name) {
+			pr_err("VALIDATE C-TBL[%zu]: Null\n", i);
+			good = false;
+		} else if (i > 0 && tbl[i - 1].name) {
+			int c = strcmp(tbl[i-1].name, tbl[i].name);
+
+			if (c == 0) {
+				pr_err("VALIDATE C-TBL[%zu]: Duplicate %s\n",
+				       i, tbl[i].name);
+				good = false;
+			}
+			if (c > 0) {
+				pr_err("VALIDATE C-TBL[%zu]: Missorted %s>=%s\n",
+				       i, tbl[i-1].name, tbl[i].name);
+				good = false;
+			}
+		}
+
+		if (tbl[i].value != special &&
+		    (tbl[i].value < low || tbl[i].value > high)) {
+			pr_err("VALIDATE C-TBL[%zu]: %s->%d const out of range (%d-%d)\n",
+			       i, tbl[i].name, tbl[i].value, low, high);
+			good = false;
+		}
+	}
+
+	if (!good)
+		dump_stack();
+	return good;
+}
+
+/**
+ * fs_validate_description - Validate a parameter description
+ * @desc: The parameter description to validate.
+ */
+bool fs_validate_description(const struct fs_parameter_description *desc)
+{
+	const char *name = desc->name;
+	bool good = true, dump = true, enums = false;
+	int i, j;
+
+	if (!name[0]) {
+		pr_err("Parser: No name\n");
+		name = "Unknown";
+		good = false;
+	}
+
+	if (desc->nr_params) {
+		if (!desc->specs) {
+			pr_err("%s: Parser: Missing types table\n", name);
+			good = false;
+			goto no_specs;
+		}
+
+		for (i = 0; i < desc->nr_params; i++) {
+			enum fs_parameter_type t = desc->specs[i].type;
+			if (t == __fs_param_wasnt_defined) {
+				pr_err("%s: Parser: [%u] Undefined type\n",
+				       name, i);
+				good = false;
+			} else if (t >= nr__fs_parameter_type) {
+				pr_err("%s: Parser: [%u] Bad type %u\n",
+				       name, i, t);
+				good = false;
+			} else if (t == fs_param_is_enum) {
+				enums = true;
+			}
+		}
+	}
+
+no_specs:
+	if (desc->nr_keys) {
+		if (!desc->nr_params) {
+			pr_err("%s: Parser: %u keys but 0 params\n",
+			       name, desc->nr_keys);
+			good = false;
+			goto no_keys;
+		}
+		if (!desc->keys) {
+			pr_err("%s: Parser: Missing keys table\n", name);
+			good = false;
+			goto no_keys;
+		}
+
+		if (!validate_constant_table(desc->keys, desc->nr_keys,
+					     0, desc->nr_params - 1,
+					     fsconfig_key_removed)) {
+			pr_err("%s: Parser: Bad keys table\n", name);
+			good = false;
+			dump = false;
+		}
+
+		/* The "source" key is used to convey the device/source
+		 * information.
+		 */
+		if (__lookup_constant(desc->keys, desc->nr_keys,
+				      "source", -1234) == -1234) {
+			if (!desc->no_source) {
+				pr_err("%s: Parser: Source key, but marked no_source\n",
+				       name);
+				good = false;
+			}
+		} else {
+			if (desc->no_source) {
+				pr_err("%s: Parser: Marked no_source, but no source key\n",
+				       name);
+				good = false;
+			}
+		}
+	}
+
+no_keys:
+	if (desc->nr_enums) {
+		if (!enums) {
+			pr_err("%s: Parser: Enum table but no enum-type values\n",
+			       name);
+			good = false;
+			goto no_enums;
+		}
+		if (!desc->enums) {
+			pr_err("%s: Parser: Missing enums table\n", name);
+			good = false;
+			goto no_enums;
+		}
+
+		for (j = 0; j < desc->nr_enums; j++) {
+			const struct fs_parameter_enum *e = &desc->enums[j];
+
+			if (!e->name[0]) {
+				pr_err("%s: Parser: e[%u] no name\n", name, j);
+				good = false;
+			}
+			if (e->param_id >= desc->nr_params) {
+				pr_err("%s: Parser: e[%u] bad param %u\n",
+				       name, j, e->param_id);
+				good = false;
+			}
+			if (desc->specs[e->param_id].type != fs_param_is_enum) {
+				pr_err("%s: Parser: e[%u] enum val for non-enum type %u\n",
+				       name, j, e->param_id);
+				good = false;
+			}
+		}
+
+		for (i = 0; i < desc->nr_params; i++) {
+			if (desc->specs[i].type != fs_param_is_enum)
+				continue;
+			for (j = 0; j < desc->nr_enums; j++)
+				if (desc->enums[j].param_id == i)
+					break;
+			if (j == desc->nr_enums) {
+				pr_err("%s: Parser: t[%u] enum with no vals\n",
+				       name, i);
+				good = false;
+			}
+		}
+	} else {
+		if (enums) {
+			pr_err("%s: Parser: enum-type values, but no enum table\n",
+			       name);
+			good = false;
+			goto no_enums;
+		}
+	}
+
+no_enums:
+	if (!good && dump)
+		dump_stack();
+	return good;
+}
+#endif /* CONFIG_VALIDATE_FS_PARSER */
diff --git a/fs/internal.h b/fs/internal.h
index 383ee4724f77..f11b834ff1e6 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -52,6 +52,8 @@ extern void __init chrdev_init(void);
 /*
  * namei.c
  */
+extern int filename_lookup(int dfd, struct filename *name, unsigned flags,
+			   struct path *path, struct path *root);
 extern int user_path_mountpoint_at(int, const char __user *, unsigned int, struct path *);
 extern int vfs_path_lookup(struct dentry *, struct vfsmount *,
 			   const char *, unsigned int, struct path *);
diff --git a/fs/namei.c b/fs/namei.c
index 734cef54fdf8..097f6ec1ae0e 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2306,8 +2306,8 @@ static int path_lookupat(struct nameidata *nd, unsigned flags, struct path *path
 	return err;
 }
 
-static int filename_lookup(int dfd, struct filename *name, unsigned flags,
-			   struct path *path, struct path *root)
+int filename_lookup(int dfd, struct filename *name, unsigned flags,
+		    struct path *path, struct path *root)
 {
 	int retval;
 	struct nameidata nd;
diff --git a/include/linux/fs_parser.h b/include/linux/fs_parser.h
new file mode 100644
index 000000000000..a5ba9b1d87c6
--- /dev/null
+++ b/include/linux/fs_parser.h
@@ -0,0 +1,116 @@
+/* Filesystem parameter description and parser
+ *
+ * Copyright (C) 2018 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#ifndef _LINUX_FS_PARSER_H
+#define _LINUX_FS_PARSER_H
+
+#include <linux/fs_context.h>
+
+struct path;
+
+struct constant_table {
+	const char	*name;
+	int		value;
+};
+
+#define fsconfig_key_removed	-5678	/* Parameter name is no longer valid */
+
+/*
+ * The type of parameter expected.
+ */
+enum fs_parameter_type {
+	__fs_param_wasnt_defined,
+	fs_param_takes_no_value,
+	fs_param_is_bool,
+	fs_param_is_u32,
+	fs_param_is_u32_octal,
+	fs_param_is_u32_hex,
+	fs_param_is_s32,
+	fs_param_is_enum,
+	fs_param_is_string,
+	fs_param_is_blob,
+	fs_param_is_blockdev,
+	fs_param_is_path,
+	fs_param_is_fd,
+	nr__fs_parameter_type,
+};
+
+/*
+ * Specification of the type of value a parameter wants.
+ */
+struct fs_parameter_spec {
+	enum fs_parameter_type	type:8;	/* The desired parameter type */
+	u8			flags;
+#define fs_param_v_optional	0x01	/* The value is optional */
+#define fs_param_neg_with_no	0x02	/* "noxxx" is negative param */
+#define fs_param_neg_with_empty	0x04	/* "xxx=" is negative param */
+#define fs_param_deprecated	0x08	/* The param is deprecated */
+};
+
+struct fs_parameter_enum {
+	u8		param_id;
+	char		name[14];
+	u8		value;
+};
+
+struct fs_parameter_description {
+	const char	name[16];	/* Name for logging purposes */
+	u8		nr_params;	/* Number of parameter IDs */
+	u8		nr_keys;	/* Number of key names */
+	u8		nr_enums;	/* Number of enum value names */
+	bool		ignore_unknown;	/* Set to ignore unknown parameters */
+	bool		no_source;	/* Set if no source is expected */
+	const struct constant_table *keys; /* List of key names */
+	const struct fs_parameter_spec *specs; /* List of param specifications */
+	const struct fs_parameter_enum *enums; /* Enum values */
+};
+
+/*
+ * Result of parse.
+ */
+struct fs_parse_result {
+	struct fs_parameter_spec t;
+	u8			key;		/* Looked up key ID */
+	bool			negated;	/* T if param was "noxxx" */
+	union {
+		bool		boolean;	/* For spec_bool */
+		int		int_32;		/* For spec_s32/spec_enum */
+		unsigned int	uint_32;	/* For spec_u32{,_octal,_hex}/spec_enum */
+	};
+};
+
+extern int fs_parse(struct fs_context *fc,
+		    const struct fs_parameter_description *desc,
+		    struct fs_parameter *value,
+		    struct fs_parse_result *result);
+extern int fs_lookup_param(struct fs_context *fc,
+			   const struct fs_parameter_description *desc,
+			   struct fs_parameter *param,
+			   struct fs_parse_result *result,
+			   struct path *_path);
+
+extern int __lookup_constant(const struct constant_table tbl[], size_t tbl_size,
+			     const char *name, int not_found);
+#define lookup_constant(t, n, nf) __lookup_constant(t, ARRAY_SIZE(t), (n), (nf))
+
+#ifdef CONFIG_VALIDATE_FS_PARSER
+extern bool validate_constant_table(const struct constant_table *tbl, size_t tbl_size,
+				    int low, int high, int special);
+extern bool fs_validate_description(const struct fs_parameter_description *desc);
+#else
+static inline bool validate_constant_table(const struct constant_table *tbl, size_t tbl_size,
+					   int low, int high, int special)
+{ return true; }
+static inline bool fs_validate_description(const struct fs_parameter_description *desc)
+{ return true; }
+#endif
+
+#endif /* _LINUX_FS_PARSER_H */
