[RFC PATCH 4/8] vfs: Convert pstore to fs_context

[David Howells]

Signed-off-by: David Howells <dhowe...@redhat.com>
cc: Kees Cook <keesc...@chromium.org>
cc: Anton Vorontsov <an...@enomsg.org>
cc: Colin Cross <ccr...@android.com>
cc: Tony Luck <tony.l...@intel.com>
---

 fs/pstore/inode.c |  110 ++++++++++++++++++++++++++++++++++-------------------
 1 file changed, 71 insertions(+), 39 deletions(-)

diff --git a/fs/pstore/inode.c b/fs/pstore/inode.c
index c60ee46f3e39..4625246fa992 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) {
@@ -416,14 +423,38 @@ static int pstore_fill_super(struct super_block *sb, void 
*data, int silent)
                return -ENOMEM;
 
        pstore_get_records(0);
-
        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 +466,8 @@ 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,
 };