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authorCarmeli Tamir <carmeli.tamir@gmail.com>2019-01-03 15:27:53 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2019-01-04 13:13:47 -0800
commitb553337a57cf4f077464292520f4e975ea4cda83 (patch)
tree1f31297f5cc7b06eb9ae84b4a2ae3f00fbe55d24
parent9da22854761a76c45d78aa2ae2b4bbd504b4f171 (diff)
downloadlinux-b553337a57cf4f077464292520f4e975ea4cda83.tar.gz
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>
-rw-r--r--fs/fat/inode.c12
-rw-r--r--include/uapi/linux/msdos_fs.h3
2 files changed, 8 insertions, 7 deletions
diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index c0b5b5c3373b..269e7b91b8b1 100644
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -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;
diff --git a/include/uapi/linux/msdos_fs.h b/include/uapi/linux/msdos_fs.h
index 1216e6caf59b..833c7079a1e3 100644
--- a/include/uapi/linux/msdos_fs.h
+++ b/include/uapi/linux/msdos_fs.h
@@ -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