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Message-ID: <20260204071435.602246-1-chizhiling@163.com>
Date: Wed,  4 Feb 2026 15:14:32 +0800
From: Chi Zhiling <chizhiling@....com>
To: linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: Namjae Jeon <linkinjeon@...nel.org>,
	Sungjong Seo <sj1557.seo@...sung.com>,
	Yuezhang Mo <yuezhang.mo@...y.com>,
	Chi Zhiling <chizhiling@...inos.cn>
Subject: 

From: Chi Zhiling <chizhiling@...inos.cn>

Subject: [PATCH v1 0/3] exfat: optimize exfat_chain_cont_cluster for large file conversion

When an exFAT file cannot allocate contiguous space, it converts from
NO_FAT_CHAIN to FAT_CHAIN format. For large files, this conversion can
be extremely slow due to:
1. Sequential FAT block reads without readahead
2. Mark buffer dirty and mirroring operations for each cluster

This series addresses these bottlenecks through two optimizations:

1. Block readahead: Read-ahead consecutive FAT blocks to reduce I/O wait
2. Buffer caching: Cache buffer heads and commit dirty buffer per block
   instead of per cluster

Performance improvements for converting a 30GB file:
| Cluster Size | Original | After Patches | Speedup |
|--------------|----------|---------------|---------|
| 512 bytes    | 47.667s  | 1.866s        | 25.5x   |
| 4KB          | 6.436s   | 0.236s        | 27.3x   |
| 32KB         | 0.758s   | 0.034s        | 22.3x   |
| 256KB        | 0.117s   | 0.006s        | 19.5x   |

All criticism and suggestions are welcome :)


Chi Zhiling (3):
  exfat: add block readahead in exfat_chain_cont_cluster
  exfat: drop parameter sec for exfat_mirror_bh
  exfat: optimize exfat_chain_cont_cluster with cached buffer heads

 fs/exfat/exfat_fs.h |  9 ++++-
 fs/exfat/fatent.c   | 96 ++++++++++++++++++++++++++++++++++++---------
 2 files changed, 85 insertions(+), 20 deletions(-)

-- 
2.43.0