From: Mike Lockwood <[email protected]>
This patch, originally from Android kernel, adds vfat directory ioctl command
FAT_IOCTL_GET_VOLUME_ID, with this command we can get the vfat volume ID using
following code:
ioctl(dirfd(dir), FAT_IOCTL_GET_VOLUME_ID, &volume_ID)
This patch is a modified version of the patch by Mike Lockwood, with changes
from Dmitry Pervushin, who noticed the original patch makes some volume IDs
abiguous with error returns: for example, if volume id is 0xFFFFFDAD, that
matches -ENOIOCTLCMD, we get "FFFFFFFF" from the user space.
So add a parameter to ioctl to get the correct volume ID.
Cc: dmitry pervushin <[email protected]>
Cc: Mike Lockwood <[email protected]>
Cc: Colin Cross <[email protected]>
Cc: Android Kernel Team <[email protected]>
Cc: OGAWA Hirofumi <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: John Stultz <[email protected]>
Signed-off-by: Bintian Wang <[email protected]>
---
fs/fat/dir.c | 14 ++++++++++++++
fs/fat/fat.h | 1 +
fs/fat/inode.c | 9 +++++++++
include/uapi/linux/msdos_fs.h | 13 +++++++++++++
4 files changed, 37 insertions(+)
diff --git a/fs/fat/dir.c b/fs/fat/dir.c
index 7a6f02c..4c59108 100644
--- a/fs/fat/dir.c
+++ b/fs/fat/dir.c
@@ -776,12 +776,19 @@ static int fat_ioctl_readdir(struct inode *inode, struct file *filp,
return ret;
}
+static unsigned int fat_ioctl_volume_id(struct inode *inode)
+{
+ struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
+ return sbi->vol_id;
+}
+
static long fat_dir_ioctl(struct file *filp, unsigned int cmd,
unsigned long arg)
{
struct inode *inode = file_inode(filp);
struct __fat_dirent __user *d1 = (struct __fat_dirent __user *)arg;
int short_only, both;
+ unsigned int id;
switch (cmd) {
case VFAT_IOCTL_READDIR_SHORT:
@@ -792,6 +799,9 @@ static long fat_dir_ioctl(struct file *filp, unsigned int cmd,
short_only = 0;
both = 1;
break;
+ case FAT_IOCTL_GET_VOLUME_ID:
+ id = fat_ioctl_volume_id(inode);
+ return copy_to_user((unsigned int *)arg, &id, sizeof(id));
default:
return fat_generic_ioctl(filp, cmd, arg);
}
@@ -822,6 +832,7 @@ static long fat_compat_dir_ioctl(struct file *filp, unsigned cmd,
struct inode *inode = file_inode(filp);
struct compat_dirent __user *d1 = compat_ptr(arg);
int short_only, both;
+ unsigned int id;
switch (cmd) {
case VFAT_IOCTL_READDIR_SHORT32:
@@ -832,6 +843,9 @@ static long fat_compat_dir_ioctl(struct file *filp, unsigned cmd,
short_only = 0;
both = 1;
break;
+ case FAT_IOCTL_GET_VOLUME_ID:
+ id = fat_ioctl_volume_id(inode);
+ return copy_to_user((unsigned int *)arg, &id, sizeof(id));
default:
return fat_generic_ioctl(filp, cmd, (unsigned long)arg);
}
diff --git a/fs/fat/fat.h b/fs/fat/fat.h
index 21664fc..4241e6f 100644
--- a/fs/fat/fat.h
+++ b/fs/fat/fat.h
@@ -86,6 +86,7 @@ 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 int 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 5d4513c..a14dd4c 100644
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -1252,6 +1252,7 @@ int fat_fill_super(struct super_block *sb, void *data, int silent, int isvfat,
struct inode *fsinfo_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;
@@ -1398,6 +1399,8 @@ int fat_fill_super(struct super_block *sb, void *data, int silent, int isvfat,
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)) {
fat_msg(sb, KERN_WARNING, "Invalid FSINFO signature: "
@@ -1413,8 +1416,14 @@ int fat_fill_super(struct super_block *sb, void *data, int silent, int isvfat,
}
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/uapi/linux/msdos_fs.h b/include/uapi/linux/msdos_fs.h
index f055e58..be142ee 100644
--- a/include/uapi/linux/msdos_fs.h
+++ b/include/uapi/linux/msdos_fs.h
@@ -104,6 +104,8 @@ 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)
+/*Android kernel has used 0x12, so we use 0x13*/
+#define FAT_IOCTL_GET_VOLUME_ID _IOR('r', 0x13, __u32)
struct fat_boot_sector {
__u8 ignored[3]; /* Boot strap short or near jump */
@@ -161,6 +163,17 @@ 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 */
--
1.7.9.5
[email protected] writes:
> This patch, originally from Android kernel, adds vfat directory ioctl command
> FAT_IOCTL_GET_VOLUME_ID, with this command we can get the vfat volume ID using
> following code:
>
> ioctl(dirfd(dir), FAT_IOCTL_GET_VOLUME_ID, &volume_ID)
>
> This patch is a modified version of the patch by Mike Lockwood, with changes
> from Dmitry Pervushin, who noticed the original patch makes some volume IDs
> abiguous with error returns: for example, if volume id is 0xFFFFFDAD, that
> matches -ENOIOCTLCMD, we get "FFFFFFFF" from the user space.
>
> So add a parameter to ioctl to get the correct volume ID.
Adding more specific usage example to changelog would help for
understanding this.
> + case FAT_IOCTL_GET_VOLUME_ID:
> + id = fat_ioctl_volume_id(inode);
> + return copy_to_user((unsigned int *)arg, &id, sizeof(id));
> + case FAT_IOCTL_GET_VOLUME_ID:
> + id = fat_ioctl_volume_id(inode);
> + return copy_to_user((unsigned int *)arg, &id, sizeof(id));
This pattern seems to from put_user().
Unnecessary cast of 1st arg. And copy_to_user() returns remaining bytes
when fail (not error code).
> +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 */
There is any issue to merge those to "struct fat_boot_sector"? I guess,
merging it is cleaner way.
Thanks.
--
OGAWA Hirofumi <[email protected]>
OGAWA Hirofumi <[email protected]> writes:
>> + case FAT_IOCTL_GET_VOLUME_ID:
>> + id = fat_ioctl_volume_id(inode);
>> + return copy_to_user((unsigned int *)arg, &id, sizeof(id));
>
>> + case FAT_IOCTL_GET_VOLUME_ID:
>> + id = fat_ioctl_volume_id(inode);
>> + return copy_to_user((unsigned int *)arg, &id, sizeof(id));
>
> This pattern seems to from put_user().
>
> Unnecessary cast of 1st arg. And copy_to_user() returns remaining bytes
> when fail (not error code).
Ah, actually, this needs cast, but it is to annotate for sparse. Well,
is there any reason to restrict this only on the directory?
For now, fat_generic_ioctl() looks easier way to do this.
(fat_generic_ioctl() should work for the both of compat code and dir/file)
Thanks.
--
OGAWA Hirofumi <[email protected]>
dmitry pervushin <[email protected]> writes:
> Hello Bintian,
>
> The original idea discussed with John was to allow
> FAT_IOCTL_GET_VOLUME_ID (broken or not) only on directory nodes, and
> even on the root directory node. That's why it is should be *not* in
> fat_generic_ioctl.
The question would be, why do we have to limit only on directory?
When I'm reviewing this, I recalled fstatvfs(2) as referenced one. The
both get the info of fs. fstatvfs(2) doesn't limit only on
directory. But, in the FAT_IOCTL_GET_VOLUME_ID case, it limits.
I wonder why?
Thanks.
--
OGAWA Hirofumi <[email protected]>