ramfs: add support for "mode=" mount option

Addresses http://bugzilla.kernel.org/show_bug.cgi?id=12843

"I use ramfs instead of tmpfs for /tmp because I don't use swap on my
laptop.  Some apps need 1777 mode for /tmp directory, but ramfs does not
support 'mode=' mount option."

Reported-by: Avan Anishchuk <matimatik@gmail.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/ramfs/inode.c b/fs/ramfs/inode.c
index b7e6ac706b87b30ba96701b3bb7820e47f319218..a404fb88e4569ff63ef9cc001216519d702c577c 100644 (file)
--- a/fs/ramfs/inode.c
+++ b/fs/ramfs/inode.c
@@ -33,12 +33,15 @@
 #include <linux/backing-dev.h>
 #include <linux/ramfs.h>
 #include <linux/sched.h>
+#include <linux/parser.h>
 #include <asm/uaccess.h>
 #include "internal.h"
 
 /* some random number */
 #define RAMFS_MAGIC    0x858458f6
 
+#define RAMFS_DEFAULT_MODE     0755
+
 static const struct super_operations ramfs_ops;
 static const struct inode_operations ramfs_dir_inode_operations;
 
@@ -158,12 +161,75 @@ static const struct inode_operations ramfs_dir_inode_operations = {
 static const struct super_operations ramfs_ops = {
        .statfs         = simple_statfs,
        .drop_inode     = generic_delete_inode,
+       .show_options   = generic_show_options,
+};
+
+struct ramfs_mount_opts {
+       umode_t mode;
+};
+
+enum {
+       Opt_mode,
+       Opt_err
+};
+
+static const match_table_t tokens = {
+       {Opt_mode, "mode=%o"},
+       {Opt_err, NULL}
+};
+
+struct ramfs_fs_info {
+       struct ramfs_mount_opts mount_opts;
 };
 
+static int ramfs_parse_options(char *data, struct ramfs_mount_opts *opts)
+{
+       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;
+               default:
+                       printk(KERN_ERR "ramfs: bad mount option: %s\n", p);
+                       return -EINVAL;
+               }
+       }
+
+       return 0;
+}
+
 static int ramfs_fill_super(struct super_block * sb, void * data, int silent)
 {
-       struct inode * inode;
-       struct dentry * root;
+       struct ramfs_fs_info *fsi;
+       struct inode *inode = NULL;
+       struct dentry *root;
+       int err;
+
+       save_mount_options(sb, data);
+
+       fsi = kzalloc(sizeof(struct ramfs_fs_info), GFP_KERNEL);
+       if (!fsi) {
+               err = -ENOMEM;
+               goto fail;
+       }
+       sb->s_fs_info = fsi;
+
+       err = ramfs_parse_options(data, &fsi->mount_opts);
+       if (err)
+               goto fail;
 
        sb->s_maxbytes = MAX_LFS_FILESIZE;
        sb->s_blocksize = PAGE_CACHE_SIZE;
@@ -171,17 +237,23 @@ static int ramfs_fill_super(struct super_block * sb, void * data, int silent)
        sb->s_magic = RAMFS_MAGIC;
        sb->s_op = &ramfs_ops;
        sb->s_time_gran = 1;
-       inode = ramfs_get_inode(sb, S_IFDIR | 0755, 0);
-       if (!inode)
-               return -ENOMEM;
+       inode = ramfs_get_inode(sb, S_IFDIR | fsi->mount_opts.mode, 0);
+       if (!inode) {
+               err = -ENOMEM;
+               goto fail;
+       }
 
        root = d_alloc_root(inode);
        if (!root) {
-               iput(inode);
-               return -ENOMEM;
+               err = -ENOMEM;
+               goto fail;
        }
        sb->s_root = root;
        return 0;
+fail:
+       kfree(fsi);
+       iput(inode);
+       return err;
 }
 
 int ramfs_get_sb(struct file_system_type *fs_type,
@@ -197,10 +269,16 @@ static int rootfs_get_sb(struct file_system_type *fs_type,
                            mnt);
 }
 
+static void ramfs_kill_sb(struct super_block *sb)
+{
+       kfree(sb->s_fs_info);
+       kill_litter_super(sb);
+}
+
 static struct file_system_type ramfs_fs_type = {
        .name           = "ramfs",
        .get_sb         = ramfs_get_sb,
-       .kill_sb        = kill_litter_super,
+       .kill_sb        = ramfs_kill_sb,
 };
 static struct file_system_type rootfs_fs_type = {
        .name           = "rootfs",