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fat: remove FAT_FIRST_ENT macro

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The comment edited in this patch was the only reference to the
FAT_FIRST_ENT macro, which is not used anymore.  Moreover, the commented
line of code does not compile with the current code.

Since the FAT_FIRST_ENT macro checks the FAT variant in a way that the
patch series changes, I removed it, and instead wrote a clear
explanation of what was checked.

I verified that the changed comment is correct according to Microsoft
FAT spec, search for "BPB_Media" in the following references:

1. Microsoft FAT specification 2005
(http://read.pudn.com/downloads77/ebook/294884/FAT32%20Spec%20%28SDA%20Contribution%29.pdf).
Search for 'volume label'.
2. Microsoft Extensible Firmware Initiative, FAT32 File System Specification
(https://staff.washington.edu/dittrich/misc/fatgen103.pdf).
Search for 'volume label'.

Link: http://lkml.kernel.org/r/1544990640-11604-2-git-send-email-carmeli.tamir@gmail.com
Signed-off-by: Carmeli Tamir <carmeli.tamir@gmail.com>
Acked-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Bart Van Assche <bvanassche@acm.org>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Carmeli Tamir 2019-01-03 15:27:53 -08:00 committed by Linus Torvalds
parent 9da2285476
commit b553337a57
2 changed files with 8 additions and 7 deletions
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12
fs/fat/inode.c
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@ -1803,11 +1803,15 @@ int fat_fill_super(struct super_block *sb, void *data, int silent, int isvfat,
fat_ent_access_init(sb);
/*
* The low byte of FAT's first entry must have same value with
* media-field. But in real world, too many devices is
* writing wrong value. So, removed that validity check.
* The low byte of the first FAT entry must have the same value as
* the media field of the boot sector. But in real world, too many
* devices are writing wrong values. So, removed that validity check.
*
* if (FAT_FIRST_ENT(sb, media) != first)
* The removed check compared the first FAT entry to a value dependent
* on the media field like this:
* == (0x0F00 | media), for FAT12
* == (0XFF00 | media), for FAT16
* == (0x0FFFFF | media), for FAT32
*/
error = -EINVAL;

3
include/uapi/linux/msdos_fs.h
View File

@ -58,9 +58,6 @@
#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