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>

1 files changed, 86 insertions, 8 deletions

diff --git a/fs/ramfs/inode.c b/fs/ramfs/inode.c
index b7e6ac706b87..a404fb88e456 100644
--- 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",