Re: [PATCH v4 00/11] exfat: convert to iomap

[Christoph Hellwig <hch@lst.de>]

So with all the reviews in we need to figure out how to merge
this.  Does merging the iomap part through the vfs tree and
pulling that into the exfat tree work for you?

On Mon, May 18, 2026 at 08:46:54PM +0900, Namjae Jeon wrote:
> This patch series converts the exfat filesystem to the iomap framework for
> buffered I/O, direct I/O, and llseek (SEEK_HOLE/SEEK_DATA) support.
> 
> iozone benchmark results (4KB cluster size, -s1g -r64k, 1GB file, 64KB record size)
> 
>                        1 thread                  4 threads
>                      Write      Read           Write      Read
>                      (MB/s)    (MB/s)         (MB/s)    (MB/s)
> -----------------------------------------------------------------
> exfat + iomap patch   332.7     418.1           78.6      82.4
> Current exfat         278.4     415.1           42.1      38.0
> -----------------------------------------------------------------
> Improvement           +19.5%    +0.7%          +86.7%   +117.4%
> 
> 
> Available in the Git repository at:
> ===================================
> git://git.kernel.org/pub/scm/linux/kernel/git/linkinjeon/exfat.git iomap-work
> 
> v4:
>   - Declare initialized variables before uninitialized ones in
>     __iomap_write_begin.
>   - Clean up the logic for handling ei->valid_size in the non-alloc
>     iomap read path.
>   - Rename exfat_cluster_to_phys to exfat_cluster_to_phys_bytes.
>   - Use end variable in exfat_fallback_buffered_write.
> 
> v3:
>   - Remove extra >> 9 when adding to inode->i_blocks.
>   - Simplify exfat_file_open() by removing unnecessary err variable.
>   - Separate exfat_truncate() error return conversion from iomap changes.
>   - Fix xfstests failures with 512B cluster size.
>   - Make exfat_truncate() return error code.
>   - Use inode lock to protect valid_size in exfat_extend_valid_size().
>   - Unify num_clusters calculation regardless of may_alloc.
>   - Use min_t() to clamp iomap->length.
>   - Return early in exfat_write_iomap_end() if no data written.
>   - Remove s_lock in exfat_write_iomap_end().
>   - Split DIO fallback buffered write into helper function.
>   - Remove unnecessary goto in exfat_dio_write_iter().
> 
> v2:
>   - Replace macros with static inline functions.
>   - Remove noop_direct_IO.
>   - Consolidate read and write iomap_begin into __exfat_iomap_begin()
>   - Zero out stale data in straddle block beyond valid_size.
>   - Introduce IOMAP_F_ZERO_TAIL flag to remove exfat_iomap_put_folio().
>   - Select FS_IOMAP in Kconfig.
>   - Remove unnecessary alignment check in exfat_file_read_iter().
>   - Just use generic_file_llseek directly.
>   - Move exfat_extend_valid_size to exfat_file_write_iter().
>   - Use pagecache_isize_extended() to remove iomap_zero_range in
>     exfat_setattr().
>   - fix mmap write data corruption with byte-by-byte fallocate.
>   - Remove exfat_mkwrite_iomap_begin().
> 
> Namjae Jeon (11):
>   iomap: introduce IOMAP_F_ZERO_TAIL flag
>   exfat: replace unsafe macros with static inline functions
>   exfat: add balloc parameter to exfat_map_cluster() for iomap support
>   exfat: add exfat_file_open()
>   exfat: add support for multi-cluster allocation
>   exfat: add data_start_bytes and exfat_cluster_to_phys_bytes() helper
>   exfat: fix implicit declaration of brelse()
>   exfat: add iomap buffered I/O support
>   exfat: add iomap direct I/O support
>   exfat: add support for SEEK_HOLE and SEEK_DATA in llseek
>   exfat: make exfat_truncate() return error code
> 
>  fs/exfat/Kconfig       |   2 +-
>  fs/exfat/Makefile      |   2 +-
>  fs/exfat/balloc.c      |   2 +-
>  fs/exfat/dir.c         |  50 +++---
>  fs/exfat/exfat_fs.h    | 140 ++++++++++++-----
>  fs/exfat/fatent.c      |  30 ++--
>  fs/exfat/file.c        | 263 +++++++++++++++++++++++--------
>  fs/exfat/inode.c       | 342 ++++++-----------------------------------
>  fs/exfat/iomap.c       | 263 +++++++++++++++++++++++++++++++
>  fs/exfat/iomap.h       |  15 ++
>  fs/exfat/namei.c       |  28 ++--
>  fs/exfat/super.c       |   5 +-
>  fs/iomap/buffered-io.c |   4 +
>  include/linux/iomap.h  |   4 +
>  14 files changed, 703 insertions(+), 447 deletions(-)
>  create mode 100644 fs/exfat/iomap.c
>  create mode 100644 fs/exfat/iomap.h
> 
> -- 
> 2.25.1
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