Commit 9fd68867 authored by Namjae Jeon's avatar Namjae Jeon
Browse files

exfat: optimize allocation bitmap loading time 



Loading the allocation bitmap is very slow if user set the small cluster
size on large partition.

For optimizing it, This patch uses sb_breadahead() read the allocation
bitmap. It will improve the mount time.

The following is the result of about 4TB partition(2KB cluster size)
on my target.

without patch:
real 0m41.746s
user 0m0.011s
sys 0m0.000s

with patch:
real 0m2.525s
user 0m0.008s
sys 0m0.008s

Reviewed-by: default avatarSungjong Seo <sj1557.seo@samsung.com>
Reviewed-by: default avatarYuezhang Mo <Yuezhang.Mo@sony.com>
Signed-off-by: default avatarNamjae Jeon <linkinjeon@kernel.org>
parent cb8d6d4a

fs/exfat/balloc.c

+13 −0
Original line number Diff line number Diff line
@@ -7,6 +7,7 @@ 
#include <linux/slab.h>

#include <linux/bitmap.h>

#include <linux/buffer_head.h>

#include <linux/backing-dev.h>



#include "exfat_raw.h"

#include "exfat_fs.h"
@@ -73,9 +74,11 @@ static int exfat_allocate_bitmap(struct super_block *sb, 
		struct exfat_dentry *ep)

{

	struct exfat_sb_info *sbi = EXFAT_SB(sb);

	struct blk_plug plug;

	long long map_size;

	unsigned int i, j, need_map_size;

	sector_t sector;

	unsigned int max_ra_count;



	sbi->map_clu = le32_to_cpu(ep->dentry.bitmap.start_clu);

	map_size = le64_to_cpu(ep->dentry.bitmap.size);
@@ -99,7 +102,17 @@ static int exfat_allocate_bitmap(struct super_block *sb, 
		return -ENOMEM;



	sector = exfat_cluster_to_sector(sbi, sbi->map_clu);

	max_ra_count = min(sb->s_bdi->ra_pages, sb->s_bdi->io_pages) <<

		(PAGE_SHIFT - sb->s_blocksize_bits);

	for (i = 0; i < sbi->map_sectors; i++) {

		/* Trigger the next readahead in advance. */

		if (0 == (i % max_ra_count)) {

			blk_start_plug(&plug);

			for (j = i; j < min(max_ra_count, sbi->map_sectors - i) + i; j++)

				sb_breadahead(sb, sector + j);

			blk_finish_plug(&plug);

		}



		sbi->vol_amap[i] = sb_bread(sb, sector + i);

		if (!sbi->vol_amap[i])

			goto err_out;