Re: [PATCH] Speedup FAT filesystem directory reads

[OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>]

Karsten Wiese <annabellesgarden@yahoo.de> writes:

> Please give this a try and commit to -mm or mainline, if approved.

Looks good. Thanks.  However, I tweaked the patch.

    - replace __getblk() to sb_getblk()
    - exclude root-dir of FAT12/FAT16 from readahead
    - exclude (sec_per_clus == 1) from readahead
    - move the all readahead stuff to one inline function

What do you think of the following patch?
-- 
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>


Signed-off-by: Karsten Wiese <annabellesgarden@yahoo.de>
Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
---

 fs/fat/dir.c |   28 ++++++++++++++++++++++++++--
 1 files changed, 26 insertions(+), 2 deletions(-)

diff -puN fs/fat/dir.c~fat-sb_breadahead fs/fat/dir.c
--- linux-2.6.13-rc4/fs/fat/dir.c~fat-sb_breadahead	2005-08-04 21:21:59.000000000 +0900
+++ linux-2.6.13-rc4-hirofumi/fs/fat/dir.c	2005-08-04 23:05:58.000000000 +0900
@@ -30,6 +30,29 @@ static inline loff_t fat_make_i_pos(stru
 		| (de - (struct msdos_dir_entry *)bh->b_data);
 }
 
+static inline void fat_dir_readahead(struct inode *dir, sector_t iblock,
+				     sector_t phys)
+{
+	struct super_block *sb = dir->i_sb;
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	struct buffer_head *bh;
+	int sec;
+
+	/* This is not a first sector of cluster, or sec_per_clus == 1 */
+	if ((iblock & (sbi->sec_per_clus - 1)) || sbi->sec_per_clus == 1)
+		return;
+	/* root dir of FAT12/FAT16 */
+	if ((sbi->fat_bits != 32) && (dir->i_ino == MSDOS_ROOT_INO))
+		return;
+
+	bh = sb_getblk(sb, phys);
+	if (bh && !buffer_uptodate(bh)) {
+		for (sec = 0; sec < sbi->sec_per_clus; sec++)
+			sb_breadahead(sb, phys + sec);
+	}
+	brelse(bh);
+}
+
 /* Returns the inode number of the directory entry at offset pos. If bh is
    non-NULL, it is brelse'd before. Pos is incremented. The buffer header is
    returned in bh.
@@ -58,6 +81,8 @@ next:
 	if (err || !phys)
 		return -1;	/* beyond EOF or error */
 
+	fat_dir_readahead(dir, iblock, phys);
+
 	*bh = sb_bread(sb, phys);
 	if (*bh == NULL) {
 		printk(KERN_ERR "FAT: Directory bread(block %llu) failed\n",
@@ -635,8 +660,7 @@ RecEnd:
 EODir:
 	filp->f_pos = cpos;
 FillFailed:
-	if (bh)
-		brelse(bh);
+	brelse(bh);
 	if (unicode)
 		free_page((unsigned long)unicode);
 out:
_