This simple patch makes the linux fat filesystem driver use the
next_cluster field in the fat_boot_fsinfo structure.  This field is a hint
where to start looking for free clusters.

Using this field makes a big difference for disks connected over slow links
such as USB 1.1.  Finding the first free cluster on a 40gig fat-formatted
usb disk can today take several minutes.  This patch cuts it down to a
fraction of a second.



 25-akpm/fs/fat/inode.c           |    1 +
 25-akpm/fs/fat/misc.c            |    1 +
 25-akpm/include/linux/msdos_fs.h |    3 +--
 3 files changed, 3 insertions(+), 2 deletions(-)

diff -puN fs/fat/inode.c~fat-speedup fs/fat/inode.c
--- 25/fs/fat/inode.c~fat-speedup	Tue Apr 22 14:40:34 2003
+++ 25-akpm/fs/fat/inode.c	Tue Apr 22 14:40:34 2003
@@ -897,6 +897,7 @@ int fat_fill_super(struct super_block *s
 			       sbi->fsinfo_sector);
 		} else {
 			sbi->free_clusters = CF_LE_L(fsinfo->free_clusters);
+			sbi->prev_free = CF_LE_L(fsinfo->next_cluster);
 		}
 
 		brelse(fsinfo_bh);
diff -puN fs/fat/misc.c~fat-speedup fs/fat/misc.c
--- 25/fs/fat/misc.c~fat-speedup	Tue Apr 22 14:40:34 2003
+++ 25-akpm/fs/fat/misc.c	Tue Apr 22 14:40:34 2003
@@ -74,6 +74,7 @@ void fat_clusters_flush(struct super_blo
 		       MSDOS_SB(sb)->fsinfo_sector);
 	} else {
 		fsinfo->free_clusters = CF_LE_L(MSDOS_SB(sb)->free_clusters);
+		fsinfo->next_cluster = CF_LE_L(MSDOS_SB(sb)->prev_free);
 		mark_buffer_dirty(bh);
 	}
 	brelse(bh);
diff -puN include/linux/msdos_fs.h~fat-speedup include/linux/msdos_fs.h
--- 25/include/linux/msdos_fs.h~fat-speedup	Tue Apr 22 14:40:34 2003
+++ 25-akpm/include/linux/msdos_fs.h	Tue Apr 22 14:40:34 2003
@@ -146,8 +146,7 @@ struct fat_boot_fsinfo {
 	__u32   reserved1[120];	/* Nothing as far as I can tell */
 	__u32   signature2;	/* 0x61417272L */
 	__u32   free_clusters;	/* Free cluster count.  -1 if unknown */
-	__u32   next_cluster;	/* Most recently allocated cluster.
-				 * Unused under Linux. */
+	__u32   next_cluster;	/* Most recently allocated cluster */
 	__u32   reserved2[4];
 };
 

_