Message-ID: <155258003937.13720.18351716241563842940.stgit@warthog.procyon.org.uk>
Date:   Thu, 14 Mar 2019 16:13:59 +0000
From:   David Howells <dhowells@...hat.com>
To:     viro@...iv.linux.org.uk
Cc:     Hugh Dickins <hughd@...gle.com>, linux-mm@...ck.org,
        dhowells@...hat.com, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 38/38] tmpfs, devtmpfs, ramfs, rootfs: Convert to fs_context

Convert tmpfs to fs_context as the mpol= option can be properly handled.
The issue is that it can contain embedded commas, so it can't be trivially
split up using strsep() to break on commas in generic_parse_monolithic().
Instead, tmpfs must supply its own generic parser.

However, if tmpfs changes, then devtmpfs and rootfs, which are wrappers around
tmpfs or ramfs, must change too - and thus so must ramfs, so convert these
also.

Signed-off-by: David Howells <dhowells@...hat.com>
cc: Hugh Dickins <hughd@...gle.com>
cc: linux-mm@...ck.org
---

 drivers/base/devtmpfs.c  |   16 +-
 fs/ramfs/inode.c         |  104 +++++++-----
 include/linux/ramfs.h    |    6 -
 include/linux/shmem_fs.h |    4 
 init/do_mounts.c         |   12 +
 mm/shmem.c               |  396 ++++++++++++++++++++++++++++++----------------
 6 files changed, 341 insertions(+), 197 deletions(-)

diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c
index 0dbc43068eeb..1f50c844c2ab 100644
--- a/drivers/base/devtmpfs.c
+++ b/drivers/base/devtmpfs.c
@@ -56,19 +56,15 @@ static int __init mount_param(char *str)
 }
 __setup("devtmpfs.mount=", mount_param);
 
-static struct dentry *dev_mount(struct file_system_type *fs_type, int flags,
-		      const char *dev_name, void *data)
-{
+static struct file_system_type dev_fs_type = {
+	.name = "devtmpfs",
 #ifdef CONFIG_TMPFS
-	return mount_single(fs_type, flags, data, shmem_fill_super);
+	.init_fs_context = shmem_init_fs_context,
+	.parameters	= &shmem_fs_parameters,
 #else
-	return mount_single(fs_type, flags, data, ramfs_fill_super);
+	.init_fs_context = ramfs_init_fs_context,
+	.parameters	= &ramfs_fs_parameters,
 #endif
-}
-
-static struct file_system_type dev_fs_type = {
-	.name = "devtmpfs",
-	.mount = dev_mount,
 	.kill_sb = kill_litter_super,
 };
 
diff --git a/fs/ramfs/inode.c b/fs/ramfs/inode.c
index 11201b2d06b9..01170dd6c95f 100644
--- a/fs/ramfs/inode.c
+++ b/fs/ramfs/inode.c
@@ -36,6 +36,8 @@
 #include <linux/magic.h>
 #include <linux/slab.h>
 #include <linux/uaccess.h>
+#include <linux/fs_context.h>
+#include <linux/fs_parser.h>
 #include "internal.h"
 
 struct ramfs_mount_opts {
@@ -175,62 +177,52 @@ static const struct super_operations ramfs_ops = {
 	.show_options	= ramfs_show_options,
 };
 
-enum {
+enum ramfs_param {
 	Opt_mode,
-	Opt_err
 };
 
-static const match_table_t tokens = {
-	{Opt_mode, "mode=%o"},
-	{Opt_err, NULL}
+static const struct fs_parameter_spec ramfs_param_specs[] = {
+	fsparam_u32oct("mode",	Opt_mode),
+	{}
 };
 
-static int ramfs_parse_options(char *data, struct ramfs_mount_opts *opts)
+const struct fs_parameter_description ramfs_fs_parameters = {
+	.name		= "ramfs",
+	.specs		= ramfs_param_specs,
+};
+
+static int ramfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
 {
-	substring_t args[MAX_OPT_ARGS];
-	int option;
-	int token;
-	char *p;
-
-	opts->mode = RAMFS_DEFAULT_MODE;
-
-	while ((p = strsep(&data, ",")) != NULL) {
-		if (!*p)
-			continue;
-
-		token = match_token(p, tokens, args);
-		switch (token) {
-		case Opt_mode:
-			if (match_octal(&args[0], &option))
-				return -EINVAL;
-			opts->mode = option & S_IALLUGO;
-			break;
+	struct fs_parse_result result;
+	struct ramfs_fs_info *fsi = fc->s_fs_info;
+	int opt;
+
+	opt = fs_parse(fc, &ramfs_fs_parameters, param, &result);
+	if (opt < 0) {
 		/*
 		 * We might like to report bad mount options here;
 		 * but traditionally ramfs has ignored all mount options,
 		 * and as it is used as a !CONFIG_SHMEM simple substitute
 		 * for tmpfs, better continue to ignore other mount options.
 		 */
-		}
+		if (opt == -ENOPARAM)
+			opt = 0;
+		return opt;
+	}
+
+	switch (opt) {
+	case Opt_mode:
+		fsi->mount_opts.mode = result.uint_32 & S_IALLUGO;
+		break;
 	}
 
 	return 0;
 }
 
-int ramfs_fill_super(struct super_block *sb, void *data, int silent)
+static int ramfs_fill_super(struct super_block *sb, struct fs_context *fc)
 {
-	struct ramfs_fs_info *fsi;
+	struct ramfs_fs_info *fsi = sb->s_fs_info;
 	struct inode *inode;
-	int err;
-
-	fsi = kzalloc(sizeof(struct ramfs_fs_info), GFP_KERNEL);
-	sb->s_fs_info = fsi;
-	if (!fsi)
-		return -ENOMEM;
-
-	err = ramfs_parse_options(data, &fsi->mount_opts);
-	if (err)
-		return err;
 
 	sb->s_maxbytes		= MAX_LFS_FILESIZE;
 	sb->s_blocksize		= PAGE_SIZE;
@@ -247,10 +239,39 @@ int ramfs_fill_super(struct super_block *sb, void *data, int silent)
 	return 0;
 }
 
-struct dentry *ramfs_mount(struct file_system_type *fs_type,
-	int flags, const char *dev_name, void *data)
+static int ramfs_get_tree(struct fs_context *fc)
 {
-	return mount_nodev(fs_type, flags, data, ramfs_fill_super);
+	enum vfs_get_super_keying keying = vfs_get_independent_super;
+
+	if (strcmp(fc->fs_type->name, "devtmpfs") == 0)
+		keying = vfs_get_single_super;
+
+	return vfs_get_super(fc, keying, ramfs_fill_super);
+}
+
+static void ramfs_free_fc(struct fs_context *fc)
+{
+	kfree(fc->s_fs_info);
+}
+
+static const struct fs_context_operations ramfs_context_ops = {
+	.free		= ramfs_free_fc,
+	.parse_param	= ramfs_parse_param,
+	.get_tree	= ramfs_get_tree,
+};
+
+int ramfs_init_fs_context(struct fs_context *fc)
+{
+	struct ramfs_fs_info *fsi;
+
+	fsi = kzalloc(sizeof(*fsi), GFP_KERNEL);
+	if (!fsi)
+		return -ENOMEM;
+
+	fsi->mount_opts.mode = RAMFS_DEFAULT_MODE;
+	fc->s_fs_info = fsi;
+	fc->ops = &ramfs_context_ops;
+	return 0;
 }
 
 static void ramfs_kill_sb(struct super_block *sb)
@@ -261,7 +282,8 @@ static void ramfs_kill_sb(struct super_block *sb)
 
 static struct file_system_type ramfs_fs_type = {
 	.name		= "ramfs",
-	.mount		= ramfs_mount,
+	.init_fs_context = ramfs_init_fs_context,
+	.parameters	= &ramfs_fs_parameters,
 	.kill_sb	= ramfs_kill_sb,
 	.fs_flags	= FS_USERNS_MOUNT,
 };
diff --git a/include/linux/ramfs.h b/include/linux/ramfs.h
index 5ef7d54caac2..94b407424cb7 100644
--- a/include/linux/ramfs.h
+++ b/include/linux/ramfs.h
@@ -4,8 +4,7 @@
 
 struct inode *ramfs_get_inode(struct super_block *sb, const struct inode *dir,
 	 umode_t mode, dev_t dev);
-extern struct dentry *ramfs_mount(struct file_system_type *fs_type,
-	 int flags, const char *dev_name, void *data);
+extern int ramfs_init_fs_context(struct fs_context *fc);
 
 #ifdef CONFIG_MMU
 static inline int
@@ -17,10 +16,9 @@ ramfs_nommu_expand_for_mapping(struct inode *inode, size_t newsize)
 extern int ramfs_nommu_expand_for_mapping(struct inode *inode, size_t newsize);
 #endif
 
+extern const struct fs_parameter_description ramfs_fs_parameters;
 extern const struct file_operations ramfs_file_operations;
 extern const struct vm_operations_struct generic_file_vm_ops;
 extern int __init init_ramfs_fs(void);
 
-int ramfs_fill_super(struct super_block *sb, void *data, int silent);
-
 #endif
diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h
index f3fb1edb3526..3f73c00081e8 100644
--- a/include/linux/shmem_fs.h
+++ b/include/linux/shmem_fs.h
@@ -48,8 +48,10 @@ static inline struct shmem_inode_info *SHMEM_I(struct inode *inode)
 /*
  * Functions in mm/shmem.c called directly from elsewhere:
  */
+extern const struct fs_parameter_description shmem_fs_parameters;
+
 extern int shmem_init(void);
-extern int shmem_fill_super(struct super_block *sb, void *data, int silent);
+extern int shmem_init_fs_context(struct fs_context *fc);
 extern struct file *shmem_file_setup(const char *name,
 					loff_t size, unsigned long flags);
 extern struct file *shmem_kernel_file_setup(const char *name, loff_t size,
diff --git a/init/do_mounts.c b/init/do_mounts.c
index f8c230c77035..8242abd47e3f 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -626,24 +626,22 @@ void __init prepare_namespace(void)
 }
 
 static bool is_tmpfs;
-static struct dentry *rootfs_mount(struct file_system_type *fs_type,
-	int flags, const char *dev_name, void *data)
+static int rootfs_init_fs_context(struct fs_context *fc)
 {
 	static unsigned long once;
-	void *fill = ramfs_fill_super;
 
 	if (test_and_set_bit(0, &once))
-		return ERR_PTR(-ENODEV);
+		return -ENODEV;
 
 	if (IS_ENABLED(CONFIG_TMPFS) && is_tmpfs)
-		fill = shmem_fill_super;
+		return shmem_init_fs_context(fc);
 
-	return mount_nodev(fs_type, flags, data, fill);
+	return ramfs_init_fs_context(fc);
 }
 
 static struct file_system_type rootfs_fs_type = {
 	.name		= "rootfs",
-	.mount		= rootfs_mount,
+	.init_fs_context = rootfs_init_fs_context,
 	.kill_sb	= kill_litter_super,
 };
 
diff --git a/mm/shmem.c b/mm/shmem.c
index b3db3779a30a..5f45a710ee04 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -37,6 +37,8 @@
 #include <linux/khugepaged.h>
 #include <linux/hugetlb.h>
 #include <linux/frontswap.h>
+#include <linux/fs_context.h>
+#include <linux/fs_parser.h>
 
 #include <asm/tlbflush.h> /* for arch/microblaze update_mmu_cache() */
 
@@ -85,6 +87,17 @@ static struct vfsmount *shm_mnt;
 
 #include "internal.h"
 
+struct shmem_fs_context {
+	unsigned long	changes;
+	unsigned long	max_blocks;	/* How many blocks are allowed */
+	unsigned long	max_inodes;	/* How many inodes are allowed */
+	kuid_t		uid;
+	kgid_t		gid;
+	int		huge;
+	umode_t		mode;
+	struct mempolicy *mpol;		/* default memory policy for mappings */
+};
+
 #define BLOCKS_PER_PAGE  (PAGE_SIZE/512)
 #define VM_ACCT(size)    (PAGE_ALIGN(size) >> PAGE_SHIFT)
 
@@ -3351,16 +3364,13 @@ static const struct export_operations shmem_export_ops = {
 	.fh_to_dentry	= shmem_fh_to_dentry,
 };
 
-static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo,
-			       bool remount)
+static int shmem_parse_monolithic(struct fs_context *fc, void *data)
 {
-	char *this_char, *value, *rest;
-	struct mempolicy *mpol = NULL;
-	uid_t uid;
-	gid_t gid;
+	char *options = data, *key;
+	int ret = 0;
 
 	while (options != NULL) {
-		this_char = options;
+		key = options;
 		for (;;) {
 			/*
 			 * NUL-terminate this option: unfortunately,
@@ -3376,139 +3386,219 @@ static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo,
 				break;
 			}
 		}
-		if (!*this_char)
-			continue;
-		if ((value = strchr(this_char,'=')) != NULL) {
-			*value++ = 0;
-		} else {
-			pr_err("tmpfs: No value for mount option '%s'\n",
-			       this_char);
-			goto error;
-		}
 
-		if (!strcmp(this_char,"size")) {
-			unsigned long long size;
-			size = memparse(value,&rest);
-			if (*rest == '%') {
-				size <<= PAGE_SHIFT;
-				size *= totalram_pages();
-				do_div(size, 100);
-				rest++;
+		if (*key) {
+			size_t v_len = 0;
+			char *value = strchr(key, '=');
+
+			if (value) {
+				if (value == key)
+					continue;
+				*value++ = 0;
+				v_len = strlen(value);
 			}
-			if (*rest)
-				goto bad_val;
-			sbinfo->max_blocks =
-				DIV_ROUND_UP(size, PAGE_SIZE);
-		} else if (!strcmp(this_char,"nr_blocks")) {
-			sbinfo->max_blocks = memparse(value, &rest);
-			if (*rest)
-				goto bad_val;
-		} else if (!strcmp(this_char,"nr_inodes")) {
-			sbinfo->max_inodes = memparse(value, &rest);
-			if (*rest)
-				goto bad_val;
-		} else if (!strcmp(this_char,"mode")) {
-			if (remount)
-				continue;
-			sbinfo->mode = simple_strtoul(value, &rest, 8) & 07777;
-			if (*rest)
-				goto bad_val;
-		} else if (!strcmp(this_char,"uid")) {
-			if (remount)
-				continue;
-			uid = simple_strtoul(value, &rest, 0);
-			if (*rest)
-				goto bad_val;
-			sbinfo->uid = make_kuid(current_user_ns(), uid);
-			if (!uid_valid(sbinfo->uid))
-				goto bad_val;
-		} else if (!strcmp(this_char,"gid")) {
-			if (remount)
-				continue;
-			gid = simple_strtoul(value, &rest, 0);
-			if (*rest)
-				goto bad_val;
-			sbinfo->gid = make_kgid(current_user_ns(), gid);
-			if (!gid_valid(sbinfo->gid))
-				goto bad_val;
+			ret = vfs_parse_fs_string(fc, key, value, v_len);
+			if (ret < 0)
+				break;
+		}
+	}
+
+	return ret;
+}
+
+enum shmem_param {
+	Opt_gid,
+	Opt_huge,
+	Opt_mode,
+	Opt_mpol,
+	Opt_nr_blocks,
+	Opt_nr_inodes,
+	Opt_size,
+	Opt_uid,
+};
+
+static const struct fs_parameter_spec shmem_param_specs[] = {
+	fsparam_u32   ("gid",		Opt_gid),
+	fsparam_enum  ("huge",		Opt_huge),
+	fsparam_u32oct("mode",		Opt_mode),
+	fsparam_string("mpol",		Opt_mpol),
+	fsparam_string("nr_blocks",	Opt_nr_blocks),
+	fsparam_string("nr_inodes",	Opt_nr_inodes),
+	fsparam_string("size",		Opt_size),
+	fsparam_u32   ("uid",		Opt_uid),
+	{}
+};
+
+static const struct fs_parameter_enum shmem_param_enums[] = {
+	{ Opt_huge,	"never",	SHMEM_HUGE_NEVER },
+	{ Opt_huge,	"always",	SHMEM_HUGE_ALWAYS },
+	{ Opt_huge,	"within_size",	SHMEM_HUGE_WITHIN_SIZE },
+	{ Opt_huge,	"advise",	SHMEM_HUGE_ADVISE },
+	{ Opt_huge,	"deny",		SHMEM_HUGE_DENY },
+	{ Opt_huge,	"force",	SHMEM_HUGE_FORCE },
+	{}
+};
+
+const struct fs_parameter_description shmem_fs_parameters = {
+	.name		= "shmem",
+	.specs		= shmem_param_specs,
+	.enums		= shmem_param_enums,
+};
+
+static void shmem_apply_options(struct shmem_sb_info *sbinfo,
+				struct fs_context *fc,
+				unsigned long inodes_in_use)
+{
+	struct shmem_fs_context *ctx = fc->fs_private;
+	struct mempolicy *old = NULL;
+
+	if (test_bit(Opt_nr_blocks, &ctx->changes))
+		sbinfo->max_blocks = ctx->max_blocks;
+	if (test_bit(Opt_nr_inodes, &ctx->changes)) {
+		sbinfo->max_inodes = ctx->max_inodes;
+		sbinfo->free_inodes = ctx->max_inodes - inodes_in_use;
+	}
+	if (test_bit(Opt_huge, &ctx->changes))
+		sbinfo->huge = ctx->huge;
+	if (test_bit(Opt_mpol, &ctx->changes)) {
+		old = sbinfo->mpol;
+		sbinfo->mpol = ctx->mpol;
+	}
+
+	if (fc->purpose != FS_CONTEXT_FOR_RECONFIGURE) {
+		if (test_bit(Opt_uid, &ctx->changes))
+			sbinfo->uid = ctx->uid;
+		if (test_bit(Opt_gid, &ctx->changes))
+			sbinfo->gid = ctx->gid;
+		if (test_bit(Opt_mode, &ctx->changes))
+			sbinfo->mode = ctx->mode;
+	}
+
+	mpol_put(old);
+}
+
+static int shmem_parse_param(struct fs_context *fc, struct fs_parameter *param)
+{
+	struct shmem_fs_context *ctx = fc->fs_private;
+	struct fs_parse_result result;
+	unsigned long long size;
+	struct mempolicy *mpol;
+	char *rest;
+	int opt;
+
+	opt = fs_parse(fc, &shmem_fs_parameters, param, &result);
+	if (opt < 0)
+		return opt;
+
+	switch (opt) {
+	case Opt_size:
+		rest = param->string;
+		size = memparse(param->string, &rest);
+		if (*rest == '%') {
+			size <<= PAGE_SHIFT;
+			size *= totalram_pages();
+			do_div(size, 100);
+			rest++;
+		}
+		if (*rest)
+			return invalf(fc, "shmem: Invalid size");
+		ctx->max_blocks = DIV_ROUND_UP(size, PAGE_SIZE);
+		break;
+
+	case Opt_nr_blocks:
+		rest = param->string;
+		ctx->max_blocks = memparse(param->string, &rest);
+		if (*rest)
+			return invalf(fc, "shmem: Invalid nr_blocks");
+		break;
+	case Opt_nr_inodes:
+		rest = param->string;
+		ctx->max_inodes = memparse(param->string, &rest);
+		if (*rest)
+			return invalf(fc, "shmem: Invalid nr_inodes");
+		break;
+	case Opt_mode:
+		ctx->mode = result.uint_32 & 07777;
+		break;
+	case Opt_uid:
+		ctx->uid = make_kuid(current_user_ns(), result.uint_32);
+		if (!uid_valid(ctx->uid))
+			return invalf(fc, "shmem: Invalid uid");
+		break;
+
+	case Opt_gid:
+		ctx->gid = make_kgid(current_user_ns(), result.uint_32);
+		if (!gid_valid(ctx->gid))
+			return invalf(fc, "shmem: Invalid gid");
+		break;
+
+	case Opt_huge:
 #ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
-		} else if (!strcmp(this_char, "huge")) {
-			int huge;
-			huge = shmem_parse_huge(value);
-			if (huge < 0)
-				goto bad_val;
-			if (!has_transparent_hugepage() &&
-					huge != SHMEM_HUGE_NEVER)
-				goto bad_val;
-			sbinfo->huge = huge;
+		if (!has_transparent_hugepage() &&
+		    result.uint_32 != SHMEM_HUGE_NEVER)
+			return invalf(fc, "shmem: Huge pages disabled");
+
+		ctx->huge = result.uint_32;
+		break;
+#else
+		return invalf(fc, "shmem: huge= option disabled");
 #endif
+
+	case Opt_mpol:
 #ifdef CONFIG_NUMA
-		} else if (!strcmp(this_char,"mpol")) {
-			mpol_put(mpol);
-			mpol = NULL;
-			if (mpol_parse_str(value, &mpol))
-				goto bad_val;
+		if (mpol_parse_str(param->string, &mpol))
+			return invalf(fc, "shmem: Invalid mpol=");
+		mpol_put(ctx->mpol);
+		ctx->mpol = mpol;
 #endif
-		} else {
-			pr_err("tmpfs: Bad mount option %s\n", this_char);
-			goto error;
-		}
+		break;
 	}
-	sbinfo->mpol = mpol;
-	return 0;
-
-bad_val:
-	pr_err("tmpfs: Bad value '%s' for mount option '%s'\n",
-	       value, this_char);
-error:
-	mpol_put(mpol);
-	return 1;
 
+	__set_bit(opt, &ctx->changes);
+	return 0;
 }
 
-static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
+/*
+ * Reconfigure a shmem filesystem.
+ *
+ * Note that we disallow change from limited->unlimited blocks/inodes while any
+ * are in use; but we must separately disallow unlimited->limited, because in
+ * that case we have no record of how much is already in use.
+ */
+static int shmem_reconfigure(struct fs_context *fc)
 {
+	struct shmem_fs_context *ctx = fc->fs_private;
+	struct super_block *sb = fc->root->d_sb;
 	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
-	struct shmem_sb_info config = *sbinfo;
-	unsigned long inodes;
-	int error = -EINVAL;
-
-	config.mpol = NULL;
-	if (shmem_parse_options(data, &config, true))
-		return error;
+	unsigned long inodes_in_use;
 
 	spin_lock(&sbinfo->stat_lock);
-	inodes = sbinfo->max_inodes - sbinfo->free_inodes;
-	if (percpu_counter_compare(&sbinfo->used_blocks, config.max_blocks) > 0)
-		goto out;
-	if (config.max_inodes < inodes)
-		goto out;
-	/*
-	 * Those tests disallow limited->unlimited while any are in use;
-	 * but we must separately disallow unlimited->limited, because
-	 * in that case we have no record of how much is already in use.
-	 */
-	if (config.max_blocks && !sbinfo->max_blocks)
-		goto out;
-	if (config.max_inodes && !sbinfo->max_inodes)
-		goto out;
-
-	error = 0;
-	sbinfo->huge = config.huge;
-	sbinfo->max_blocks  = config.max_blocks;
-	sbinfo->max_inodes  = config.max_inodes;
-	sbinfo->free_inodes = config.max_inodes - inodes;
+	if (test_bit(Opt_nr_blocks, &ctx->changes)) {
+		if (ctx->max_blocks && !sbinfo->max_blocks) {
+			spin_unlock(&sbinfo->stat_lock);
+			return invalf(fc, "shmem: Can't retroactively limit nr_blocks");
+		}
+		if (percpu_counter_compare(&sbinfo->used_blocks, ctx->max_blocks) > 0) {
+			spin_unlock(&sbinfo->stat_lock);
+			return invalf(fc, "shmem: Too few blocks for current use");
+		}
+	}
 
-	/*
-	 * Preserve previous mempolicy unless mpol remount option was specified.
-	 */
-	if (config.mpol) {
-		mpol_put(sbinfo->mpol);
-		sbinfo->mpol = config.mpol;	/* transfers initial ref */
+	inodes_in_use = sbinfo->max_inodes - sbinfo->free_inodes;
+	if (test_bit(Opt_nr_inodes, &ctx->changes)) {
+		if (ctx->max_inodes && !sbinfo->max_inodes) {
+			spin_unlock(&sbinfo->stat_lock);
+			return invalf(fc, "shmem: Can't retroactively limit nr_inodes");
+		}
+		if (ctx->max_inodes < inodes_in_use) {
+			spin_unlock(&sbinfo->stat_lock);
+			return invalf(fc, "shmem: Too few inodes for current use");
+		}
 	}
-out:
+
+	shmem_apply_options(sbinfo, fc, inodes_in_use);
 	spin_unlock(&sbinfo->stat_lock);
-	return error;
+	return 0;
 }
 
 static int shmem_show_options(struct seq_file *seq, struct dentry *root)
@@ -3549,7 +3639,7 @@ static void shmem_put_super(struct super_block *sb)
 	sb->s_fs_info = NULL;
 }
 
-int shmem_fill_super(struct super_block *sb, void *data, int silent)
+static int shmem_fill_super(struct super_block *sb, struct fs_context *fc)
 {
 	struct inode *inode;
 	struct shmem_sb_info *sbinfo;
@@ -3575,10 +3665,7 @@ int shmem_fill_super(struct super_block *sb, void *data, int silent)
 	if (!(sb->s_flags & SB_KERNMOUNT)) {
 		sbinfo->max_blocks = shmem_default_max_blocks();
 		sbinfo->max_inodes = shmem_default_max_inodes();
-		if (shmem_parse_options(data, sbinfo, false)) {
-			err = -EINVAL;
-			goto failed;
-		}
+		shmem_apply_options(sbinfo, fc, 0);
 	} else {
 		sb->s_flags |= SB_NOUSER;
 	}
@@ -3624,6 +3711,36 @@ int shmem_fill_super(struct super_block *sb, void *data, int silent)
 	return err;
 }
 
+static int shmem_get_tree(struct fs_context *fc)
+{
+	enum vfs_get_super_keying keying = vfs_get_independent_super;
+
+	if (strcmp(fc->fs_type->name, "devtmpfs") == 0)
+		keying = vfs_get_single_super;
+
+	return vfs_get_super(fc, keying, shmem_fill_super);
+}
+
+static void shmem_free_fc(struct fs_context *fc)
+{
+	struct shmem_fs_context *ctx = fc->fs_private;
+
+	if (ctx) {
+		mpol_put(ctx->mpol);
+		kfree(ctx);
+	}
+}
+
+static const struct fs_context_operations shmem_fs_context_ops = {
+	.free			= shmem_free_fc,
+	.get_tree		= shmem_get_tree,
+#ifdef CONFIG_TMPFS
+	.parse_monolithic	= shmem_parse_monolithic,
+	.parse_param		= shmem_parse_param,
+	.reconfigure		= shmem_reconfigure,
+#endif
+};
+
 static struct kmem_cache *shmem_inode_cachep;
 
 static struct inode *shmem_alloc_inode(struct super_block *sb)
@@ -3741,7 +3858,6 @@ static const struct super_operations shmem_ops = {
 	.destroy_inode	= shmem_destroy_inode,
 #ifdef CONFIG_TMPFS
 	.statfs		= shmem_statfs,
-	.remount_fs	= shmem_remount_fs,
 	.show_options	= shmem_show_options,
 #endif
 	.evict_inode	= shmem_evict_inode,
@@ -3762,16 +3878,26 @@ static const struct vm_operations_struct shmem_vm_ops = {
 #endif
 };
 
-static struct dentry *shmem_mount(struct file_system_type *fs_type,
-	int flags, const char *dev_name, void *data)
+int shmem_init_fs_context(struct fs_context *fc)
 {
-	return mount_nodev(fs_type, flags, data, shmem_fill_super);
+	struct shmem_fs_context *ctx;
+
+	ctx = kzalloc(sizeof(struct shmem_fs_context), GFP_KERNEL);
+	if (!ctx)
+		return -ENOMEM;
+
+	fc->fs_private = ctx;
+	fc->ops = &shmem_fs_context_ops;
+	return 0;
 }
 
 static struct file_system_type shmem_fs_type = {
 	.owner		= THIS_MODULE,
 	.name		= "tmpfs",
-	.mount		= shmem_mount,
+	.init_fs_context = shmem_init_fs_context,
+#ifdef CONFIG_TMPFS
+	.parameters	= &shmem_fs_parameters,
+#endif
 	.kill_sb	= kill_litter_super,
 	.fs_flags	= FS_USERNS_MOUNT,
 };
@@ -3916,7 +4042,8 @@ bool shmem_huge_enabled(struct vm_area_struct *vma)
 
 static struct file_system_type shmem_fs_type = {
 	.name		= "tmpfs",
-	.mount		= ramfs_mount,
+	.init_fs_context = ramfs_init_fs_context,
+	.parameters	= &ramfs_fs_parameters,
 	.kill_sb	= kill_litter_super,
 	.fs_flags	= FS_USERNS_MOUNT,
 };
@@ -4117,3 +4244,4 @@ struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
 #endif
 }
 EXPORT_SYMBOL_GPL(shmem_read_mapping_page_gfp);
+

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