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kernel-ark/include/linux/msdos_fs.h
Artem Bityutskiy 020ac5b6be fat: introduce special inode for managing the FSINFO block 
This is patchset makes fatfs stop using the VFS '->write_super()' method
for writing out the FSINFO block.

The final goal is to get rid of the 'sync_supers()' kernel thread.  This
kernel thread wakes up every 5 seconds (by default) and calls
'->write_super()' for all mounted file-systems.  And the bad thing is that
this is done even if all the superblocks are clean.  Moreover, some
file-systems do not even need this end they do not register the
'->write_super()' method at all (e.g., btrfs).

So 'sync_supers()' most often just generates useless wake-ups and wastes
power.  I am trying to make all file-systems independent of
'->write_super()' and plan to remove 'sync_supers()' and '->write_super'
completely once there are no more users.

The '->write_supers()' method is mostly used by baroque file-systems like
hfs, udf, etc.  Modern file-systems like btrfs and xfs do not use it.
This justifies removing this stuff from VFS completely and make every FS
self-manage own superblock.

Tested with xfstests.

This patch:

Preparation for further changes.  It introduces a special inode
('fsinfo_inode') in FAT file-system which we'll later use for managing the
FSINFO block.  Note, this there is already one special inode ('fat_inode')
which is used for managing the FAT tables.

Introduce new 'MSDOS_FSINFO_INO' constant for this special inode.  It is
safe to do because FAT file-system does not store inode numbers on the
media but generates them run-time.

I've also cleaned up the comment to existing 'MSDOS_ROOT_INO' constant,
while on it.

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Cc: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-05-31 17:49:27 -07:00

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#ifndef _LINUX_MSDOS_FS_H
#define _LINUX_MSDOS_FS_H
#include <linux/types.h>
#include <linux/magic.h>
#include <asm/byteorder.h>
/*
* The MS-DOS filesystem constants/structures
*/
#define SECTOR_SIZE 512 /* sector size (bytes) */
#define SECTOR_BITS 9 /* log2(SECTOR_SIZE) */
#define MSDOS_DPB (MSDOS_DPS) /* dir entries per block */
#define MSDOS_DPB_BITS 4 /* log2(MSDOS_DPB) */
#define MSDOS_DPS (SECTOR_SIZE / sizeof(struct msdos_dir_entry))
#define MSDOS_DPS_BITS 4 /* log2(MSDOS_DPS) */
#define MSDOS_LONGNAME 256 /* maximum name length */
#define CF_LE_W(v) le16_to_cpu(v)
#define CF_LE_L(v) le32_to_cpu(v)
#define CT_LE_W(v) cpu_to_le16(v)
#define CT_LE_L(v) cpu_to_le32(v)
#define MSDOS_ROOT_INO 1 /* The root inode number */
#define MSDOS_FSINFO_INO 2 /* Used for managing the FSINFO block */
#define MSDOS_DIR_BITS 5 /* log2(sizeof(struct msdos_dir_entry)) */
/* directory limit */
#define FAT_MAX_DIR_ENTRIES (65536)
#define FAT_MAX_DIR_SIZE (FAT_MAX_DIR_ENTRIES << MSDOS_DIR_BITS)
#define ATTR_NONE 0 /* no attribute bits */
#define ATTR_RO 1 /* read-only */
#define ATTR_HIDDEN 2 /* hidden */
#define ATTR_SYS 4 /* system */
#define ATTR_VOLUME 8 /* volume label */
#define ATTR_DIR 16 /* directory */
#define ATTR_ARCH 32 /* archived */
/* attribute bits that are copied "as is" */
#define ATTR_UNUSED (ATTR_VOLUME | ATTR_ARCH | ATTR_SYS | ATTR_HIDDEN)
/* bits that are used by the Windows 95/Windows NT extended FAT */
#define ATTR_EXT (ATTR_RO | ATTR_HIDDEN | ATTR_SYS | ATTR_VOLUME)
#define CASE_LOWER_BASE 8 /* base is lower case */
#define CASE_LOWER_EXT 16 /* extension is lower case */
#define DELETED_FLAG 0xe5 /* marks file as deleted when in name[0] */
#define IS_FREE(n) (!*(n) || *(n) == DELETED_FLAG)
#define FAT_LFN_LEN 255 /* maximum long name length */
#define MSDOS_NAME 11 /* maximum name length */
#define MSDOS_SLOTS 21 /* max # of slots for short and long names */
#define MSDOS_DOT ". " /* ".", padded to MSDOS_NAME chars */
#define MSDOS_DOTDOT ".. " /* "..", padded to MSDOS_NAME chars */
#define FAT_FIRST_ENT(s, x) ((MSDOS_SB(s)->fat_bits == 32 ? 0x0FFFFF00 : \
MSDOS_SB(s)->fat_bits == 16 ? 0xFF00 : 0xF00) | (x))
/* start of data cluster's entry (number of reserved clusters) */
#define FAT_START_ENT 2
/* maximum number of clusters */
#define MAX_FAT12 0xFF4
#define MAX_FAT16 0xFFF4
#define MAX_FAT32 0x0FFFFFF6
#define MAX_FAT(s) (MSDOS_SB(s)->fat_bits == 32 ? MAX_FAT32 : \
MSDOS_SB(s)->fat_bits == 16 ? MAX_FAT16 : MAX_FAT12)
/* bad cluster mark */
#define BAD_FAT12 0xFF7
#define BAD_FAT16 0xFFF7
#define BAD_FAT32 0x0FFFFFF7
/* standard EOF */
#define EOF_FAT12 0xFFF
#define EOF_FAT16 0xFFFF
#define EOF_FAT32 0x0FFFFFFF
#define FAT_ENT_FREE (0)
#define FAT_ENT_BAD (BAD_FAT32)
#define FAT_ENT_EOF (EOF_FAT32)
#define FAT_FSINFO_SIG1 0x41615252
#define FAT_FSINFO_SIG2 0x61417272
#define IS_FSINFO(x) (le32_to_cpu((x)->signature1) == FAT_FSINFO_SIG1 \
&& le32_to_cpu((x)->signature2) == FAT_FSINFO_SIG2)
struct __fat_dirent {
long d_ino;
__kernel_off_t d_off;
unsigned short d_reclen;
char d_name[256]; /* We must not include limits.h! */
};
/*
* ioctl commands
*/
#define VFAT_IOCTL_READDIR_BOTH _IOR('r', 1, struct __fat_dirent[2])
#define VFAT_IOCTL_READDIR_SHORT _IOR('r', 2, struct __fat_dirent[2])
/* <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)
struct fat_boot_sector {
__u8 ignored[3]; /* Boot strap short or near jump */
__u8 system_id[8]; /* Name - can be used to special case
partition manager volumes */
__u8 sector_size[2]; /* bytes per logical sector */
__u8 sec_per_clus; /* sectors/cluster */
__le16 reserved; /* reserved sectors */
__u8 fats; /* number of FATs */
__u8 dir_entries[2]; /* root directory entries */
__u8 sectors[2]; /* number of sectors */
__u8 media; /* media code */
__le16 fat_length; /* sectors/FAT */
__le16 secs_track; /* sectors per track */
__le16 heads; /* number of heads */
__le32 hidden; /* hidden sectors (unused) */
__le32 total_sect; /* number of sectors (if sectors == 0) */
/* The following fields are only used by FAT32 */
__le32 fat32_length; /* sectors/FAT */
__le16 flags; /* bit 8: fat mirroring, low 4: active fat */
__u8 version[2]; /* major, minor filesystem version */
__le32 root_cluster; /* first cluster in root directory */
__le16 info_sector; /* filesystem info sector */
__le16 backup_boot; /* backup boot sector */
__le16 reserved2[6]; /* Unused */
};
struct fat_boot_fsinfo {
__le32 signature1; /* 0x41615252L */
__le32 reserved1[120]; /* Nothing as far as I can tell */
__le32 signature2; /* 0x61417272L */
__le32 free_clusters; /* Free cluster count. -1 if unknown */
__le32 next_cluster; /* Most recently allocated cluster */
__le32 reserved2[4];
};
struct msdos_dir_entry {
__u8 name[MSDOS_NAME];/* name and extension */
__u8 attr; /* attribute bits */
__u8 lcase; /* Case for base and extension */
__u8 ctime_cs; /* Creation time, centiseconds (0-199) */
__le16 ctime; /* Creation time */
__le16 cdate; /* Creation date */
__le16 adate; /* Last access date */
__le16 starthi; /* High 16 bits of cluster in FAT32 */
__le16 time,date,start;/* time, date and first cluster */
__le32 size; /* file size (in bytes) */
};
/* Up to 13 characters of the name */
struct msdos_dir_slot {
__u8 id; /* sequence number for slot */
__u8 name0_4[10]; /* first 5 characters in name */
__u8 attr; /* attribute byte */
__u8 reserved; /* always 0 */
__u8 alias_checksum; /* checksum for 8.3 alias */
__u8 name5_10[12]; /* 6 more characters in name */
__le16 start; /* starting cluster number, 0 in long slots */
__u8 name11_12[4]; /* last 2 characters in name */
};
#ifdef __KERNEL__
/* media of boot sector */
static inline int fat_valid_media(u8 media)
{
return 0xf8 <= media || media == 0xf0;
}
#endif /* !__KERNEL__ */
#endif /* !_LINUX_MSDOS_FS_H */
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