From 9fd688678dd86e3be32a35e3b2c5cc3ef0c4e257 Mon Sep 17 00:00:00 2001 From: Namjae Jeon Date: Sat, 6 Sep 2025 08:13:04 +0900 Subject: [PATCH] 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: Sungjong Seo Reviewed-by: Yuezhang Mo Signed-off-by: Namjae Jeon --- fs/exfat/balloc.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/fs/exfat/balloc.c b/fs/exfat/balloc.c index 071448adbd5d9..2d2d510f2372c 100644 --- a/fs/exfat/balloc.c +++ b/fs/exfat/balloc.c @@ -7,6 +7,7 @@ #include #include #include +#include #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; -- 2.47.3