Commit b553337a authored Jan 03, 2019 by Carmeli Tamir Committed by Linus Torvalds Jan 04, 2019

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: 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>

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

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