From: H. Peter Anvin <hpa@zytor.com>
Date: Mon, 25 Jan 2010 19:34:33 +0000 (-0800)
Subject: FAT: deal with non-mirrored FATs for FAT32
X-Git-Tag: syslinux-4.00-pre11~3
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=217683b7fca9672293d997829fdbc25d7f667e79;p=platform%2Fupstream%2Fsyslinux.git

FAT: deal with non-mirrored FATs for FAT32

FAT32 has the option of non-mirrored FATs, used to improve atomicity
of some operations.  If we have non-mirrored FATs, we need to make
sure to read the one FAT which is currently marked active.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
---

diff --git a/core/fs/fat/fat.c b/core/fs/fat/fat.c
index c89ed78..b036ead 100644
--- a/core/fs/fat/fat.c
+++ b/core/fs/fat/fat.c
@@ -743,8 +743,14 @@ static int vfat_fs_init(struct fs_info *fs)
 	sbi->fat_type = FAT16;
     } else {
 	sbi->fat_type = FAT32;
+
 	if (clusters > 0x0ffffff4)
 	    clusters = 0x0ffffff4; /* Maximum possible */
+
+	if (fat.fat32.extended_flags & 0x80) {
+	    /* Non-mirrored FATs, we need to read the active one */
+	    sbi->fat += (fat.fat32.extended_flags & 0x0f) * sectors_per_fat;
+	}
     }
     sbi->clusters = clusters;