Message-ID: <155315518700.21302.17394925275943156425.stgit@warthog.procyon.org.uk>
Date:   Thu, 21 Mar 2019 07:59:47 +0000
From:   David Howells <dhowells@...hat.com>
To:     balbi@...nel.org
Cc:     dhowells@...hat.com, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] vfs: Convert functionfs to fs_context

Signed-off-by: David Howells <dhowells@...hat.com>
cc: Felipe Balbi <balbi@...nel.org>
cc: Michał Nazarewicz <mina86@...a86.com>
cc: linux-usb@...r.kernel.org
---

 drivers/usb/gadget/function/f_fs.c |  232 ++++++++++++++++++------------------
 1 file changed, 119 insertions(+), 113 deletions(-)

diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
index 20413c276c61..1b8061cdf87c 100644
--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -17,6 +17,7 @@
 #include <linux/blkdev.h>
 #include <linux/pagemap.h>
 #include <linux/export.h>
+#include <linux/fs_parser.h>
 #include <linux/hid.h>
 #include <linux/mm.h>
 #include <linux/module.h>
@@ -1447,9 +1448,9 @@ struct ffs_sb_fill_data {
 	struct ffs_data *ffs_data;
 };
 
-static int ffs_sb_fill(struct super_block *sb, void *_data, int silent)
+static int ffs_sb_fill(struct super_block *sb, struct fs_context *fc)
 {
-	struct ffs_sb_fill_data *data = _data;
+	struct ffs_sb_fill_data *data = fc->fs_private;
 	struct inode	*inode;
 	struct ffs_data	*ffs = data->ffs_data;
 
@@ -1482,147 +1483,152 @@ static int ffs_sb_fill(struct super_block *sb, void *_data, int silent)
 	return 0;
 }
 
-static int ffs_fs_parse_opts(struct ffs_sb_fill_data *data, char *opts)
-{
-	ENTER();
+enum {
+	Opt_no_disconnect,
+	Opt_rmode,
+	Opt_fmode,
+	Opt_mode,
+	Opt_uid,
+	Opt_gid,
+};
 
-	if (!opts || !*opts)
-		return 0;
+static const struct fs_parameter_spec ffs_fs_param_specs[] = {
+	fsparam_bool	("no_disconnect",	Opt_no_disconnect),
+	fsparam_u32	("rmode",		Opt_rmode),
+	fsparam_u32	("fmode",		Opt_fmode),
+	fsparam_u32	("mode",		Opt_mode),
+	fsparam_u32	("uid",			Opt_uid),
+	fsparam_u32	("gid",			Opt_gid),
+	{}
+};
 
-	for (;;) {
-		unsigned long value;
-		char *eq, *comma;
-
-		/* Option limit */
-		comma = strchr(opts, ',');
-		if (comma)
-			*comma = 0;
-
-		/* Value limit */
-		eq = strchr(opts, '=');
-		if (unlikely(!eq)) {
-			pr_err("'=' missing in %s\n", opts);
-			return -EINVAL;
-		}
-		*eq = 0;
+static const struct fs_parameter_description ffs_fs_fs_parameters = {
+	.name		= "kAFS",
+	.specs		= ffs_fs_param_specs,
+};
 
-		/* Parse value */
-		if (kstrtoul(eq + 1, 0, &value)) {
-			pr_err("%s: invalid value: %s\n", opts, eq + 1);
-			return -EINVAL;
-		}
+static int ffs_fs_parse_param(struct fs_context *fc, struct fs_parameter *param)
+{
+	struct ffs_sb_fill_data *data = fc->fs_private;
+	struct fs_parse_result result;
+	int opt;
 
-		/* Interpret option */
-		switch (eq - opts) {
-		case 13:
-			if (!memcmp(opts, "no_disconnect", 13))
-				data->no_disconnect = !!value;
-			else
-				goto invalid;
-			break;
-		case 5:
-			if (!memcmp(opts, "rmode", 5))
-				data->root_mode  = (value & 0555) | S_IFDIR;
-			else if (!memcmp(opts, "fmode", 5))
-				data->perms.mode = (value & 0666) | S_IFREG;
-			else
-				goto invalid;
-			break;
+	ENTER();
 
-		case 4:
-			if (!memcmp(opts, "mode", 4)) {
-				data->root_mode  = (value & 0555) | S_IFDIR;
-				data->perms.mode = (value & 0666) | S_IFREG;
-			} else {
-				goto invalid;
-			}
-			break;
+	opt = fs_parse(fc, &ffs_fs_fs_parameters, param, &result);
+	if (opt < 0)
+		return opt;
 
-		case 3:
-			if (!memcmp(opts, "uid", 3)) {
-				data->perms.uid = make_kuid(current_user_ns(), value);
-				if (!uid_valid(data->perms.uid)) {
-					pr_err("%s: unmapped value: %lu\n", opts, value);
-					return -EINVAL;
-				}
-			} else if (!memcmp(opts, "gid", 3)) {
-				data->perms.gid = make_kgid(current_user_ns(), value);
-				if (!gid_valid(data->perms.gid)) {
-					pr_err("%s: unmapped value: %lu\n", opts, value);
-					return -EINVAL;
-				}
-			} else {
-				goto invalid;
-			}
-			break;
+	switch (opt) {
+	case Opt_no_disconnect:
+		data->no_disconnect = result.boolean;
+		break;
+	case Opt_rmode:
+		data->root_mode  = (result.uint_32 & 0555) | S_IFDIR;
+		break;
+	case Opt_fmode:
+		data->perms.mode = (result.uint_32 & 0666) | S_IFREG;
+		break;
+	case Opt_mode:
+		data->root_mode  = (result.uint_32 & 0555) | S_IFDIR;
+		data->perms.mode = (result.uint_32 & 0666) | S_IFREG;
+		break;
 
-		default:
-invalid:
-			pr_err("%s: invalid option\n", opts);
-			return -EINVAL;
-		}
+	case Opt_uid:
+		data->perms.uid = make_kuid(current_user_ns(), result.uint_32);
+		if (!uid_valid(data->perms.uid))
+			goto unmapped_value;
+		break;
+	case Opt_gid:
+		data->perms.gid = make_kgid(current_user_ns(), result.uint_32);
+		if (!gid_valid(data->perms.gid))
+			goto unmapped_value;
+		break;
 
-		/* Next iteration */
-		if (!comma)
-			break;
-		opts = comma + 1;
+	default:
+		return -ENOPARAM;
 	}
 
 	return 0;
-}
 
-/* "mount -t functionfs dev_name /dev/function" ends up here */
+unmapped_value:
+	return invalf(fc, "%s: unmapped value: %u", param->key, result.uint_32);
+}
 
-static struct dentry *
-ffs_fs_mount(struct file_system_type *t, int flags,
-	      const char *dev_name, void *opts)
-{
-	struct ffs_sb_fill_data data = {
-		.perms = {
-			.mode = S_IFREG | 0600,
-			.uid = GLOBAL_ROOT_UID,
-			.gid = GLOBAL_ROOT_GID,
-		},
-		.root_mode = S_IFDIR | 0500,
-		.no_disconnect = false,
-	};
-	struct dentry *rv;
-	int ret;
+/*
+ * Set up the superblock for a mount.
+ */
+static int ffs_fs_get_tree(struct fs_context *fc)
+{
+	struct ffs_sb_fill_data *ctx = fc->fs_private;
 	void *ffs_dev;
 	struct ffs_data	*ffs;
 
 	ENTER();
 
-	ret = ffs_fs_parse_opts(&data, opts);
-	if (unlikely(ret < 0))
-		return ERR_PTR(ret);
+	if (!fc->source)
+		return invalf(fc, "No source specified");
 
-	ffs = ffs_data_new(dev_name);
+	ffs = ffs_data_new(fc->source);
 	if (unlikely(!ffs))
-		return ERR_PTR(-ENOMEM);
-	ffs->file_perms = data.perms;
-	ffs->no_disconnect = data.no_disconnect;
+		return -ENOMEM;
+	ffs->file_perms = ctx->perms;
+	ffs->no_disconnect = ctx->no_disconnect;
 
-	ffs->dev_name = kstrdup(dev_name, GFP_KERNEL);
+	ffs->dev_name = kstrdup(fc->source, GFP_KERNEL);
 	if (unlikely(!ffs->dev_name)) {
 		ffs_data_put(ffs);
-		return ERR_PTR(-ENOMEM);
+		return -ENOMEM;
 	}
 
-	ffs_dev = ffs_acquire_dev(dev_name);
+	ffs_dev = ffs_acquire_dev(ffs->dev_name);
 	if (IS_ERR(ffs_dev)) {
 		ffs_data_put(ffs);
-		return ERR_CAST(ffs_dev);
+		return PTR_ERR(ffs_dev);
 	}
+
 	ffs->private_data = ffs_dev;
-	data.ffs_data = ffs;
+	ctx->ffs_data = ffs;
+	return vfs_get_super(fc, vfs_get_independent_super, ffs_sb_fill);
+}
+
+static void ffs_fs_free_fc(struct fs_context *fc)
+{
+	struct ffs_sb_fill_data *ctx = fc->fs_private;
+
+	if (ctx) {
+		if (ctx->ffs_data) {
+			ffs_release_dev(ctx->ffs_data);
+			ffs_data_put(ctx->ffs_data);
+		}
 
-	rv = mount_nodev(t, flags, &data, ffs_sb_fill);
-	if (IS_ERR(rv) && data.ffs_data) {
-		ffs_release_dev(data.ffs_data);
-		ffs_data_put(data.ffs_data);
+		kfree(ctx);
 	}
-	return rv;
+}
+
+static const struct fs_context_operations ffs_fs_context_ops = {
+	.free		= ffs_fs_free_fc,
+	.parse_param	= ffs_fs_parse_param,
+	.get_tree	= ffs_fs_get_tree,
+};
+
+static int ffs_fs_init_fs_context(struct fs_context *fc)
+{
+	struct ffs_sb_fill_data *ctx;
+
+	ctx = kzalloc(sizeof(struct ffs_sb_fill_data), GFP_KERNEL);
+	if (!ctx)
+		return -ENOMEM;
+
+	ctx->perms.mode = S_IFREG | 0600;
+	ctx->perms.uid = GLOBAL_ROOT_UID;
+	ctx->perms.gid = GLOBAL_ROOT_GID;
+	ctx->root_mode = S_IFDIR | 0500;
+	ctx->no_disconnect = false;
+
+	fc->fs_private = ctx;
+	fc->ops = &ffs_fs_context_ops;
+	return 0;
 }
 
 static void
@@ -1640,7 +1646,7 @@ ffs_fs_kill_sb(struct super_block *sb)
 static struct file_system_type ffs_fs_type = {
 	.owner		= THIS_MODULE,
 	.name		= "functionfs",
-	.mount		= ffs_fs_mount,
+	.init_fs_context = ffs_fs_init_fs_context,
 	.kill_sb	= ffs_fs_kill_sb,
 };
 MODULE_ALIAS_FS("functionfs");

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