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>

diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index c0b5b5c3373bd967f86697f9aa39b75942399877..269e7b91b8b131d58c573887512e4f0681df5ae2 100644 (file)
--- 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 1216e6caf59b0b990147b7130c4cc29f5bb4fb99..833c7079a1e3db1d04d812eefd8b41ee3f417aaa 100644 (file)
--- 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