Hello.
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.
Please Cc me on any discussion about this patch, as I am not subscribed to the list.
The patch is cooked in two flavors, for 2.4.20 and 2.5.68:
For 2.4.20:
diff -Nru include/linux.orig/msdos_fs.h include/linux/msdos_fs.h
--- include/linux.orig/msdos_fs.h Tue Apr 22 10:55:09 2003
+++ include/linux/msdos_fs.h Tue Apr 22 10:58:33 2003
@@ -145,8 +145,7 @@
__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];
};
diff -Nru fs/fat.orig/inode.c fs/fat/inode.c
--- fs/fat.orig/inode.c Sat Aug 3 02:39:45 2002
+++ fs/fat/inode.c Tue Apr 22 11:47:50 2003
@@ -637,6 +637,7 @@
sbi->cluster_bits = ffs(logical_sector_size * sbi->cluster_size) - 1;
sbi->fats = b->fats;
sbi->fat_start = CF_LE_W(b->reserved);
+ sbi->prev_free = 0;
if (!b->fat_length && b->fat32_length) {
struct fat_boot_fsinfo *fsinfo;
struct buffer_head *fsinfo_bh;
@@ -675,6 +676,7 @@
sbi->fsinfo_sector);
} else {
sbi->free_clusters = CF_LE_L(fsinfo->free_clusters);
+ sbi->prev_free = CF_LE_L(fsinfo->next_cluster);
}
if (fsinfo_block != 0)
@@ -754,7 +756,6 @@
sb->s_magic = MSDOS_SUPER_MAGIC;
/* set up enough so that it can read an inode */
init_MUTEX(&sbi->fat_lock);
- sbi->prev_free = 0;
cp = opts.codepage ? opts.codepage : 437;
sprintf(buf, "cp%d", cp);
diff -Nru fs/fat.orig/misc.c fs/fat/misc.c
--- fs/fat.orig/misc.c Fri Oct 12 22:48:42 2001
+++ fs/fat/misc.c Tue Apr 22 10:59:52 2003
@@ -108,6 +108,7 @@
return;
}
fsinfo->free_clusters = CF_LE_L(MSDOS_SB(sb)->free_clusters);
+ fsinfo->next_cluster = CF_LE_L(MSDOS_SB(sb)->prev_free);
fat_mark_buffer_dirty(sb, bh);
fat_brelse(sb, bh);
}
For 2.5.68:
--- include/linux/msdos_fs.h.orig Tue Apr 22 12:05:35 2003
+++ include/linux/msdos_fs.h Tue Apr 22 12:06:02 2003
@@ -146,8 +146,7 @@
__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];
};
--- fs/fat/inode.c.orig Tue Apr 22 12:06:12 2003
+++ fs/fat/inode.c Tue Apr 22 12:08:12 2003
@@ -898,6 +898,7 @@
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);
--- fs/fat/misc.c.orig Tue Apr 22 12:06:16 2003
+++ fs/fat/misc.c Tue Apr 22 12:06:49 2003
@@ -74,6 +74,7 @@
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);
-- Björn - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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