Re: [RFC PATCH 57/68] vfs: Convert pstore to use the new mount API
From: Kees Cook
Date: Wed Mar 27 2019 - 20:24:47 EST
On Wed, Mar 27, 2019 at 4:47 PM David Howells <dhowells@xxxxxxxxxx> wrote:
>
> Convert the pstore filesystem to the new internal mount API as the old
> one will be obsoleted and removed. This allows greater flexibility in
> communication of mount parameters between userspace, the VFS and the
> filesystem.
>
> See Documentation/filesystems/mount_api.txt for more information.
>
> Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
> cc: Kees Cook <keescook@xxxxxxxxxxxx>
> cc: Anton Vorontsov <anton@xxxxxxxxxx>
> cc: Colin Cross <ccross@xxxxxxxxxxx>
> cc: Tony Luck <tony.luck@xxxxxxxxx>
Acked-by: Kees Cook <keescook@xxxxxxxxxxxx>
-Kees
> ---
>
> fs/pstore/inode.c | 109 +++++++++++++++++++++++++++++++++++------------------
> 1 file changed, 71 insertions(+), 38 deletions(-)
>
> diff --git a/fs/pstore/inode.c b/fs/pstore/inode.c
> index c60ee46f3e39..bb4e4cabd11f 100644
> --- a/fs/pstore/inode.c
> +++ b/fs/pstore/inode.c
> @@ -19,6 +19,8 @@
>
> #include <linux/module.h>
> #include <linux/fs.h>
> +#include <linux/fs_context.h>
> +#include <linux/fs_parser.h>
> #include <linux/fsnotify.h>
> #include <linux/pagemap.h>
> #include <linux/highmem.h>
> @@ -26,10 +28,8 @@
> #include <linux/init.h>
> #include <linux/list.h>
> #include <linux/string.h>
> -#include <linux/mount.h>
> #include <linux/seq_file.h>
> #include <linux/ramfs.h>
> -#include <linux/parser.h>
> #include <linux/sched.h>
> #include <linux/magic.h>
> #include <linux/pstore.h>
> @@ -227,38 +227,48 @@ static struct inode *pstore_get_inode(struct super_block *sb)
> return inode;
> }
>
> +struct pstore_fs_context {
> + unsigned int kmsg_bytes;
> +};
> +
> enum {
> - Opt_kmsg_bytes, Opt_err
> + Opt_kmsg_bytes,
> };
>
> -static const match_table_t tokens = {
> - {Opt_kmsg_bytes, "kmsg_bytes=%u"},
> - {Opt_err, NULL}
> +static const struct fs_parameter_spec pstore_param_specs[] = {
> + fsparam_u32 ("kmsg_bytes", Opt_kmsg_bytes),
> + {}
> };
>
> -static void parse_options(char *options)
> -{
> - char *p;
> - substring_t args[MAX_OPT_ARGS];
> - int option;
> +static const struct fs_parameter_description pstore_fs_parameters = {
> + .name = "pstore",
> + .specs = pstore_param_specs,
> +};
>
> - if (!options)
> - return;
> +static int pstore_parse_param(struct fs_context *fc, struct fs_parameter *param)
> +{
> + struct pstore_fs_context *ctx = fc->fs_private;
> + struct fs_parse_result result;
> + int opt;
> +
> + opt = fs_parse(fc, &pstore_fs_parameters, param, &result);
> + if (opt < 0)
> + return opt;
> +
> + switch (opt) {
> + case Opt_kmsg_bytes:
> + ctx->kmsg_bytes = result.uint_32;
> + break;
> + }
>
> - while ((p = strsep(&options, ",")) != NULL) {
> - int token;
> + return 0;
> +}
>
> - if (!*p)
> - continue;
> +static void pstore_apply_param(struct fs_context *fc)
> +{
> + struct pstore_fs_context *ctx = fc->fs_private;
>
> - token = match_token(p, tokens, args);
> - switch (token) {
> - case Opt_kmsg_bytes:
> - if (!match_int(&args[0], &option))
> - pstore_set_kmsg_bytes(option);
> - break;
> - }
> - }
> + pstore_set_kmsg_bytes(ctx->kmsg_bytes);
> }
>
> /*
> @@ -271,11 +281,10 @@ static int pstore_show_options(struct seq_file *m, struct dentry *root)
> return 0;
> }
>
> -static int pstore_remount(struct super_block *sb, int *flags, char *data)
> +static int pstore_reconfigure(struct fs_context *fc)
> {
> - sync_filesystem(sb);
> - parse_options(data);
> -
> + sync_filesystem(fc->root->d_sb);
> + pstore_apply_param(fc);
> return 0;
> }
>
> @@ -283,7 +292,6 @@ static const struct super_operations pstore_ops = {
> .statfs = simple_statfs,
> .drop_inode = generic_delete_inode,
> .evict_inode = pstore_evict_inode,
> - .remount_fs = pstore_remount,
> .show_options = pstore_show_options,
> };
>
> @@ -389,12 +397,10 @@ void pstore_get_records(int quiet)
> inode_unlock(d_inode(root));
> }
>
> -static int pstore_fill_super(struct super_block *sb, void *data, int silent)
> +static int pstore_fill_super(struct super_block *sb, struct fs_context *fc)
> {
> struct inode *inode;
>
> - pstore_sb = sb;
> -
> sb->s_maxbytes = MAX_LFS_FILESIZE;
> sb->s_blocksize = PAGE_SIZE;
> sb->s_blocksize_bits = PAGE_SHIFT;
> @@ -402,7 +408,8 @@ static int pstore_fill_super(struct super_block *sb, void *data, int silent)
> sb->s_op = &pstore_ops;
> sb->s_time_gran = 1;
>
> - parse_options(data);
> + pstore_sb = sb;
> + pstore_apply_param(fc);
>
> inode = pstore_get_inode(sb);
> if (inode) {
> @@ -420,10 +427,35 @@ static int pstore_fill_super(struct super_block *sb, void *data, int silent)
> return 0;
> }
>
> -static struct dentry *pstore_mount(struct file_system_type *fs_type,
> - int flags, const char *dev_name, void *data)
> +static int pstore_get_tree(struct fs_context *fc)
> +{
> + return vfs_get_super(fc, vfs_get_single_reconf_super,
> + pstore_fill_super);
> +}
> +
> +static void pstore_free_fc(struct fs_context *fc)
> {
> - return mount_single(fs_type, flags, data, pstore_fill_super);
> + kfree(fc->fs_private);
> +}
> +
> +static const struct fs_context_operations pstore_context_ops = {
> + .free = pstore_free_fc,
> + .parse_param = pstore_parse_param,
> + .get_tree = pstore_get_tree,
> + .reconfigure = pstore_reconfigure,
> +};
> +
> +static int pstore_init_fs_context(struct fs_context *fc)
> +{
> + struct pstore_fs_context *ctx;
> +
> + ctx = kzalloc(sizeof(struct pstore_fs_context), GFP_KERNEL);
> + if (!ctx)
> + return -ENOMEM;
> +
> + fc->fs_private = ctx;
> + fc->ops = &pstore_context_ops;
> + return 0;
> }
>
> static void pstore_kill_sb(struct super_block *sb)
> @@ -435,7 +467,8 @@ static void pstore_kill_sb(struct super_block *sb)
> static struct file_system_type pstore_fs_type = {
> .owner = THIS_MODULE,
> .name = "pstore",
> - .mount = pstore_mount,
> + .init_fs_context = pstore_init_fs_context,
> + .parameters = &pstore_fs_parameters,
> .kill_sb = pstore_kill_sb,
> };
>
>
--
Kees Cook