FAT: Add new ioctl VFAT_IOCTL_GET_VOLUME_ID for reading the volume ID.

Signed-off-by: Brian Swetland <swetland@google.com>

diff --git a/fs/fat/dir.c b/fs/fat/dir.c
index 530b4ca0151037ae212fe9d2d8ffb827fc970f98..4ceff51104170d2650adcbd0f299ae7d1eeb34ff 100644 (file)
--- a/fs/fat/dir.c
+++ b/fs/fat/dir.c
@@ -758,6 +758,13 @@ static int fat_ioctl_readdir(struct inode *inode, struct file *filp,
        return ret;
 }
 
+static int fat_ioctl_volume_id(struct inode *dir)
+{
+       struct super_block *sb = dir->i_sb;
+       struct msdos_sb_info *sbi = MSDOS_SB(sb);
+       return sbi->vol_id;
+}
+
 static int fat_dir_ioctl(struct inode *inode, struct file *filp,
                         unsigned int cmd, unsigned long arg)
 {
@@ -773,6 +780,8 @@ static int fat_dir_ioctl(struct inode *inode, struct file *filp,
                short_only = 0;
                both = 1;
                break;
+       case VFAT_IOCTL_GET_VOLUME_ID:
+               return fat_ioctl_volume_id(inode);
        default:
                return fat_generic_ioctl(inode, filp, cmd, arg);
        }

diff --git a/fs/fat/fat.h b/fs/fat/fat.h
index 7db0979c6b72f0d16e19c77d6e73af5642992f83..4e25637d2b278f8b0306bfe078a1dc5ad3d12189 100644 (file)
--- a/fs/fat/fat.h
+++ b/fs/fat/fat.h
@@ -76,6 +76,7 @@ struct msdos_sb_info {
        const void *dir_ops;                 /* Opaque; default directory operations */
        int dir_per_block;           /* dir entries per block */
        int dir_per_block_bits;      /* log2(dir_per_block) */
+       unsigned long vol_id;        /* volume ID */
 
        int fatent_shift;
        struct fatent_operations *fatent_ops;

diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index 76b7961ab6632e5d955a9139eaa4b0652e11ff8c..81261eb3215de490c9710502d21eb2b1cf8673d2 100644 (file)
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -1215,6 +1215,7 @@ int fat_fill_super(struct super_block *sb, void *data, int silent,
        struct inode *root_inode = NULL, *fat_inode = NULL;
        struct buffer_head *bh;
        struct fat_boot_sector *b;
+       struct fat_boot_bsx *bsx;
        struct msdos_sb_info *sbi;
        u16 logical_sector_size;
        u32 total_sectors, total_clusters, fat_clusters, rootdir_sectors;
@@ -1357,6 +1358,8 @@ int fat_fill_super(struct super_block *sb, void *data, int silent,
                        goto out_fail;
                }
 
+               bsx = (struct fat_boot_bsx *)(bh->b_data + FAT32_BSX_OFFSET);
+
                fsinfo = (struct fat_boot_fsinfo *)fsinfo_bh->b_data;
                if (!IS_FSINFO(fsinfo)) {
                        printk(KERN_WARNING "FAT: Invalid FSINFO signature: "
@@ -1372,8 +1375,14 @@ int fat_fill_super(struct super_block *sb, void *data, int silent,
                }
 
                brelse(fsinfo_bh);
+       } else {
+               bsx = (struct fat_boot_bsx *)(bh->b_data + FAT16_BSX_OFFSET);
        }
 
+       /* interpret volume ID as a little endian 32 bit integer */
+       sbi->vol_id = (((u32)bsx->vol_id[0]) | ((u32)bsx->vol_id[1] << 8) |
+               ((u32)bsx->vol_id[2] << 16) | ((u32)bsx->vol_id[3] << 24));
+
        sbi->dir_per_block = sb->s_blocksize / sizeof(struct msdos_dir_entry);
        sbi->dir_per_block_bits = ffs(sbi->dir_per_block) - 1;
 

diff --git a/include/linux/msdos_fs.h b/include/linux/msdos_fs.h
index ce38f1caa5e1346e748ee0fca6d5d7b66c2aae0d..844d77ddfb34df0175bf64c4b425b273bf7bd2dd 100644 (file)
--- a/include/linux/msdos_fs.h
+++ b/include/linux/msdos_fs.h
@@ -100,6 +100,7 @@ struct __fat_dirent {
 /* <linux/videotext.h> has used 0x72 ('r') in collision, so skip a few */
 #define FAT_IOCTL_GET_ATTRIBUTES       _IOR('r', 0x10, __u32)
 #define FAT_IOCTL_SET_ATTRIBUTES       _IOW('r', 0x11, __u32)
+#define VFAT_IOCTL_GET_VOLUME_ID       _IOR('r', 0x12, __u32)
 
 struct fat_boot_sector {
        __u8    ignored[3];     /* Boot strap short or near jump */
@@ -137,6 +138,17 @@ struct fat_boot_fsinfo {
        __le32   reserved2[4];
 };
 
+struct fat_boot_bsx {
+       __u8     drive;             /* drive number */
+       __u8     reserved1;
+       __u8     signature;         /* extended boot signature */
+       __u8     vol_id[4];     /* volume ID */
+       __u8     vol_label[11]; /* volume label */
+       __u8     type[8];       /* file system type */
+};
+#define FAT16_BSX_OFFSET       36 /* offset of fat_boot_bsx in FAT12 and FAT16 */
+#define FAT32_BSX_OFFSET       64 /* offset of fat_boot_bsx in FAT32 */
+
 struct msdos_dir_entry {
        __u8    name[MSDOS_NAME];/* name and extension */
        __u8    attr;           /* attribute bits */