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Commit b553337a authored by Carmeli Tamir's avatar Carmeli Tamir Committed by Linus Torvalds
Browse files

fat: remove FAT_FIRST_ENT macro 

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: default avatarCarmeli Tamir <carmeli.tamir@gmail.com>
Acked-by: default avatarOGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Reviewed-by: default avatarSergey 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 9da22854

fs/fat/inode.c

+8 −4
Original line number Diff line number Diff line
@@ -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;

include/uapi/linux/msdos_fs.h

+0 −3
Original line number Diff line number Diff line
@@ -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