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SubjectRe: [PATCH 1/3] 24-bit types: typedef and macros for accessing 3-byte arrays as integers
Dave Kleikamp wrote:
> On Wed, 2008-09-10 at 10:07 -0400, Christoph Hellwig wrote:
>
>> JFS already defines an __le24, see fs/jfs/endian24.h. Please try to
>> cover it, too or at least make sure you don't break it.
>
> Chris,
> This patch takes care of jfs. Please add it to your patchset.
>
> Thanks,
> Shaggy
>
> 24-bit types: Convert jfs to use the common 24-bit types
>
> This patch cleans up some of the ugliness in the jfs headers and
> uses the common 24-bit types instead of its private definitions.
>
> Signed-off-by: Dave Kleikamp <shaggy@linux.vnet.ibm.com>
>
> diff --git a/fs/jfs/endian24.h b/fs/jfs/endian24.h
> deleted file mode 100644
> index fa92f7f..0000000
> --- a/fs/jfs/endian24.h
> +++ /dev/null
> @@ -1,49 +0,0 @@
> -/*
> - * Copyright (C) International Business Machines Corp., 2001
> - *
> - * This program is free software; you can redistribute it and/or modify
> - * it under the terms of the GNU General Public License as published by
> - * the Free Software Foundation; either version 2 of the License, or
> - * (at your option) any later version.
> - *
> - * This program is distributed in the hope that it will be useful,
> - * but WITHOUT ANY WARRANTY; without even the implied warranty of
> - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
> - * the GNU General Public License for more details.
> - *
> - * You should have received a copy of the GNU General Public License
> - * along with this program; if not, write to the Free Software
> - * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
> - */
> -#ifndef _H_ENDIAN24
> -#define _H_ENDIAN24
> -
> -/*
> - * endian24.h:
> - *
> - * Endian conversion for 24-byte data
> - *
> - */
> -#define __swab24(x) \
> -({ \
> - __u32 __x = (x); \
> - ((__u32)( \
> - ((__x & (__u32)0x000000ffUL) << 16) | \
> - (__x & (__u32)0x0000ff00UL) | \
> - ((__x & (__u32)0x00ff0000UL) >> 16) )); \
> -})
> -
> -#if (defined(__KERNEL__) && defined(__LITTLE_ENDIAN)) || (defined(__BYTE_ORDER) && (__BYTE_ORDER == __LITTLE_ENDIAN))
> - #define __cpu_to_le24(x) ((__u32)(x))
> - #define __le24_to_cpu(x) ((__u32)(x))
> -#else
> - #define __cpu_to_le24(x) __swab24(x)
> - #define __le24_to_cpu(x) __swab24(x)
> -#endif
> -
> -#ifdef __KERNEL__
> - #define cpu_to_le24 __cpu_to_le24
> - #define le24_to_cpu __le24_to_cpu
> -#endif
> -
> -#endif /* !_H_ENDIAN24 */
> diff --git a/fs/jfs/jfs_types.h b/fs/jfs/jfs_types.h
> index 649f981..6c49b93 100644
> --- a/fs/jfs/jfs_types.h
> +++ b/fs/jfs/jfs_types.h
> @@ -30,8 +30,6 @@
> #include <linux/types.h>
> #include <linux/nls.h>
>
> -#include "endian24.h"
> -
> /*
> * transaction and lock id's
> *
> @@ -62,7 +60,7 @@ struct timestruc_t {
> */
> typedef struct {
> unsigned len:24;
> - unsigned off1:8;
> + u8 off1;
> u32 off2;
> } lxd_t;
>

Why is the difference from below definition. That is the
use/not of __le24?

> @@ -90,8 +88,8 @@ struct lxdlist {
> * physical xd (pxd)
> */
> typedef struct {
> - unsigned len:24;
> - unsigned addr1:8;
> + __le24 len;

Is this stuff on-the-wire?
Do you need a:
+ __le24 len __packed;

> + u8 addr1;
> __le32 addr2;
> } pxd_t;
and:
} pxd_t __packed ;

>
> @@ -122,13 +120,13 @@ struct pxdlist {
> * data extent descriptor (dxd)
> */
> typedef struct {
> - unsigned flag:8; /* 1: flags */
> - unsigned rsrvd:24;
> - __le32 size; /* 4: size in byte */
> - unsigned len:24; /* 3: length in unit of fsblksize */
> - unsigned addr1:8; /* 1: address in unit of fsblksize */
> - __le32 addr2; /* 4: address in unit of fsblksize */
> -} dxd_t; /* - 16 - */
> + u8 flag; /* 1: flags */
> + u8 rsrvd[3];
> + __le32 size; /* 4: size in byte */
> + __le24 len; /* 3: length in unit of fsblksize */
> + u8 addr1; /* 1: address in unit of fsblksize */
> + __le32 addr2; /* 4: address in unit of fsblksize */
> +} dxd_t; /* - 16 - */
>
> /* dxd_t flags */
> #define DXD_INDEX 0x80 /* B+-tree index */
> diff --git a/fs/jfs/jfs_xtree.h b/fs/jfs/jfs_xtree.h
> index 70815c8..92beff3 100644
> --- a/fs/jfs/jfs_xtree.h
> +++ b/fs/jfs/jfs_xtree.h
> @@ -29,14 +29,14 @@
> * extent allocation descriptor (xad)
> */
> typedef struct xad {
> - unsigned flag:8; /* 1: flag */
> - unsigned rsvrd:16; /* 2: reserved */
> - unsigned off1:8; /* 1: offset in unit of fsblksize */
> - __le32 off2; /* 4: offset in unit of fsblksize */
> - unsigned len:24; /* 3: length in unit of fsblksize */
> - unsigned addr1:8; /* 1: address in unit of fsblksize */
> - __le32 addr2; /* 4: address in unit of fsblksize */
> -} xad_t; /* (16) */
> + u8 flag; /* 1: flag */
> + u8 rsvrd[2]; /* 2: reserved */
> + u8 off1; /* 1: offset in unit of fsblksize */
> + __le32 off2; /* 4: offset in unit of fsblksize */
> + __le24 len; /* 3: length in unit of fsblksize */
> + u8 addr1; /* 1: address in unit of fsblksize */
> + __le32 addr2; /* 4: address in unit of fsblksize */
> +} xad_t; /* (16) */
>
> #define MAXXLEN ((1 << 24) - 1)
>
>

Note that before the :24 bit-field was kept packed but now
with the use of struct at the __le24 definition it might
choose to pad them.

Chris you might want to change the definitions at linux/types.h
to:

typedef struct { __u8 b[3]; } __be24, __le24 __packed;

With gcc it will not help with the proceeding fields, and the
containing struct will need it's own "__packed" declaration
but it will keep it packed with previous fields.

Just my $0.017
Boaz


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