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Subject[PATCH v2 1/3] fat: Removed 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'.


Signed-off-by: Carmeli Tamir <carmeli.tamir@gmail.com>
---
fs/fat/inode.c | 12 ++++++++----
include/uapi/linux/msdos_fs.h | 3 ---
2 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index e981e9d..708de6d 100644
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -1804,11 +1804,15 @@ 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 1216e6c..833c707 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

--
2.7.4
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