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SubjectRe: [RFC PATCH 3/8] vfs: Convert tracefs to fs_context
On Thu, 21 Mar 2019 11:47:57 +0000
David Howells <dhowells@redhat.com> wrote:

Very weak change log (none!). What is this fs_context, and why does it
need to change? Each patch should hold its own as a stand alone, as git
history shows a patch not a series, and the cover letters will get lost
over time.

-- Steve


> Signed-off-by: David Howells <dhowells@redhat.com>
> cc: Steven Rostedt <rostedt@goodmis.org>
> cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> ---
>
> fs/tracefs/inode.c | 180 ++++++++++++++++++++++++----------------------------
> 1 file changed, 83 insertions(+), 97 deletions(-)
>
> diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
> index 7098c49f3693..7ba64f38931f 100644
> --- a/fs/tracefs/inode.c
> +++ b/fs/tracefs/inode.c
> @@ -16,12 +16,13 @@
> #include <linux/module.h>
> #include <linux/fs.h>
> #include <linux/mount.h>
> +#include <linux/fs_context.h>
> +#include <linux/fs_parser.h>
> #include <linux/kobject.h>
> #include <linux/namei.h>
> #include <linux/tracefs.h>
> #include <linux/fsnotify.h>
> #include <linux/seq_file.h>
> -#include <linux/parser.h>
> #include <linux/magic.h>
> #include <linux/slab.h>
>
> @@ -138,73 +139,62 @@ static struct inode *tracefs_get_inode(struct super_block *sb)
> return inode;
> }
>
> -struct tracefs_mount_opts {
> +struct tracefs_fs_info {
> kuid_t uid;
> kgid_t gid;
> umode_t mode;
> };
>
> enum {
> - Opt_uid,
> Opt_gid,
> Opt_mode,
> - Opt_err
> + Opt_uid,
> };
>
> -static const match_table_t tokens = {
> - {Opt_uid, "uid=%u"},
> - {Opt_gid, "gid=%u"},
> - {Opt_mode, "mode=%o"},
> - {Opt_err, NULL}
> +static const struct fs_parameter_spec tracefs_param_specs[] = {
> + fsparam_u32 ("gid", Opt_gid),
> + fsparam_u32oct ("mode", Opt_mode),
> + fsparam_u32 ("uid", Opt_uid),
> + {}
> };
>
> -struct tracefs_fs_info {
> - struct tracefs_mount_opts mount_opts;
> +static const struct fs_parameter_description tracefs_fs_parameters = {
> + .name = "tracefs",
> + .specs = tracefs_param_specs,
> };
>
> -static int tracefs_parse_options(char *data, struct tracefs_mount_opts *opts)
> +static int tracefs_parse_param(struct fs_context *fc, struct fs_parameter *param)
> {
> - substring_t args[MAX_OPT_ARGS];
> - int option;
> - int token;
> + struct tracefs_fs_info *opts = fc->s_fs_info;
> + struct fs_parse_result result;
> kuid_t uid;
> kgid_t gid;
> - char *p;
> -
> - opts->mode = TRACEFS_DEFAULT_MODE;
> -
> - while ((p = strsep(&data, ",")) != NULL) {
> - if (!*p)
> - continue;
> -
> - token = match_token(p, tokens, args);
> - switch (token) {
> - case Opt_uid:
> - if (match_int(&args[0], &option))
> - return -EINVAL;
> - uid = make_kuid(current_user_ns(), option);
> - if (!uid_valid(uid))
> - return -EINVAL;
> - opts->uid = uid;
> - break;
> - case Opt_gid:
> - if (match_int(&args[0], &option))
> - return -EINVAL;
> - gid = make_kgid(current_user_ns(), option);
> - if (!gid_valid(gid))
> - return -EINVAL;
> - opts->gid = gid;
> - break;
> - case Opt_mode:
> - if (match_octal(&args[0], &option))
> - return -EINVAL;
> - opts->mode = option & S_IALLUGO;
> - break;
> + int opt;
> +
> + opt = fs_parse(fc, &tracefs_fs_parameters, param, &result);
> + if (opt < 0)
> + return opt;
> +
> + switch (opt) {
> + case Opt_uid:
> + uid = make_kuid(current_user_ns(), result.uint_32);
> + if (!uid_valid(uid))
> + return invalf(fc, "Unknown uid");
> + opts->uid = uid;
> + break;
> + case Opt_gid:
> + gid = make_kgid(current_user_ns(), result.uint_32);
> + if (!gid_valid(gid))
> + return invalf(fc, "Unknown gid");
> + opts->gid = gid;
> + break;
> + case Opt_mode:
> + opts->mode = result.uint_32 & S_IALLUGO;
> + break;
> /*
> * We might like to report bad mount options here;
> * but traditionally tracefs has ignored all mount options
> */
> - }
> }
>
> return 0;
> @@ -214,100 +204,96 @@ static int tracefs_apply_options(struct super_block *sb)
> {
> struct tracefs_fs_info *fsi = sb->s_fs_info;
> struct inode *inode = sb->s_root->d_inode;
> - struct tracefs_mount_opts *opts = &fsi->mount_opts;
>
> inode->i_mode &= ~S_IALLUGO;
> - inode->i_mode |= opts->mode;
> + inode->i_mode |= fsi->mode;
>
> - inode->i_uid = opts->uid;
> - inode->i_gid = opts->gid;
> + inode->i_uid = fsi->uid;
> + inode->i_gid = fsi->gid;
>
> return 0;
> }
>
> -static int tracefs_remount(struct super_block *sb, int *flags, char *data)
> +static int tracefs_reconfigure(struct fs_context *fc)
> {
> - int err;
> - struct tracefs_fs_info *fsi = sb->s_fs_info;
> + struct super_block *sb = fc->root->d_sb;
>
> sync_filesystem(sb);
> - err = tracefs_parse_options(data, &fsi->mount_opts);
> - if (err)
> - goto fail;
> -
> - tracefs_apply_options(sb);
> -
> -fail:
> - return err;
> + return tracefs_apply_options(sb);
> }
>
> static int tracefs_show_options(struct seq_file *m, struct dentry *root)
> {
> struct tracefs_fs_info *fsi = root->d_sb->s_fs_info;
> - struct tracefs_mount_opts *opts = &fsi->mount_opts;
>
> - if (!uid_eq(opts->uid, GLOBAL_ROOT_UID))
> + if (!uid_eq(fsi->uid, GLOBAL_ROOT_UID))
> seq_printf(m, ",uid=%u",
> - from_kuid_munged(&init_user_ns, opts->uid));
> - if (!gid_eq(opts->gid, GLOBAL_ROOT_GID))
> + from_kuid_munged(&init_user_ns, fsi->uid));
> + if (!gid_eq(fsi->gid, GLOBAL_ROOT_GID))
> seq_printf(m, ",gid=%u",
> - from_kgid_munged(&init_user_ns, opts->gid));
> - if (opts->mode != TRACEFS_DEFAULT_MODE)
> - seq_printf(m, ",mode=%o", opts->mode);
> + from_kgid_munged(&init_user_ns, fsi->gid));
> + if (fsi->mode != TRACEFS_DEFAULT_MODE)
> + seq_printf(m, ",mode=%o", fsi->mode);
>
> return 0;
> }
>
> static const struct super_operations tracefs_super_operations = {
> .statfs = simple_statfs,
> - .remount_fs = tracefs_remount,
> .show_options = tracefs_show_options,
> };
>
> -static int trace_fill_super(struct super_block *sb, void *data, int silent)
> +static int tracefs_fill_super(struct super_block *sb, struct fs_context *fc)
> {
> static const struct tree_descr trace_files[] = {{""}};
> - struct tracefs_fs_info *fsi;
> int err;
>
> - fsi = kzalloc(sizeof(struct tracefs_fs_info), GFP_KERNEL);
> - sb->s_fs_info = fsi;
> - if (!fsi) {
> - err = -ENOMEM;
> - goto fail;
> - }
> -
> - err = tracefs_parse_options(data, &fsi->mount_opts);
> + err = simple_fill_super(sb, TRACEFS_MAGIC, trace_files);
> if (err)
> - goto fail;
> -
> - err = simple_fill_super(sb, TRACEFS_MAGIC, trace_files);
> - if (err)
> - goto fail;
> + return err;
>
> sb->s_op = &tracefs_super_operations;
> + return tracefs_apply_options(sb);
> +}
>
> - tracefs_apply_options(sb);
> -
> - return 0;
> +static int tracefs_get_tree(struct fs_context *fc)
> +{
> + return vfs_get_super(fc, vfs_get_single_reconf_super,
> + tracefs_fill_super);
> +}
>
> -fail:
> - kfree(fsi);
> - sb->s_fs_info = NULL;
> - return err;
> +static void tracefs_free_fc(struct fs_context *fc)
> +{
> + kfree(fc->s_fs_info);
> }
>
> -static struct dentry *trace_mount(struct file_system_type *fs_type,
> - int flags, const char *dev_name,
> - void *data)
> +static const struct fs_context_operations tracefs_context_ops = {
> + .free = tracefs_free_fc,
> + .parse_param = tracefs_parse_param,
> + .get_tree = tracefs_get_tree,
> + .reconfigure = tracefs_reconfigure,
> +};
> +
> +static int tracefs_init_fs_context(struct fs_context *fc)
> {
> - return mount_single(fs_type, flags, data, trace_fill_super);
> + struct tracefs_fs_info *fsi;
> +
> + fsi = kzalloc(sizeof(struct tracefs_fs_info), GFP_KERNEL);
> + if (!fsi)
> + return -ENOMEM;
> +
> + fsi->mode = TRACEFS_DEFAULT_MODE;
> +
> + fc->s_fs_info = fsi;
> + fc->ops = &tracefs_context_ops;
> + return 0;
> }
>
> static struct file_system_type trace_fs_type = {
> .owner = THIS_MODULE,
> .name = "tracefs",
> - .mount = trace_mount,
> + .init_fs_context = tracefs_init_fs_context,
> + .parameters = &tracefs_fs_parameters,
> .kill_sb = kill_litter_super,
> };
> MODULE_ALIAS_FS("tracefs");

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