Re: [PATCH v2 00/10] ext4: refactor partial block zero-out for iomap conversion

[Zhang Yi <yi.zhang@huaweicloud.com>]

On 3/25/2026 3:28 PM, Zhang Yi wrote:
> From: Zhang Yi <yi.zhang@huawei.com>

Sashiko found some real issues in patch 09 and 10, I will send v3 to fix them.

https://sashiko.dev/#/patchset/20260325072850.3997161-1-yi.zhang%40huaweicloud.com

Best Regards,
Yi.

> 
> Changes since v1:
>  - In patch 04, rename ext4_block_get_zero_range() to
>    ext4_load_tail_bh() and drop the unused 'length' parameter as Jan
>    suggested.
>  - In patch 06, modify the commit message, add another reason to drop
>    data=ordered mode when zeroing partial blocks in ext4_punch_hole()
>    and ext4_punch_hole() as Jan pointed out.
>  - In patch 10, modify the commit message, explain the race condition
>    between the buffered write and mmap write that pointed out by Jan.
>  - Collect reviewed tags from Jan.
> 
> v1: https://lore.kernel.org/linux-ext4/20260310014101.4140698-1-yi.zhang@huaweicloud.com/
> 
> Original cover letter:
> 
> This patch series extracted from my iomap conversion v2 series[1]. It
> refactors the ext4 zero partial block code path in preparation for
> converting buffered I/O to the iomap infrastructure. The main changes
> are:
> 
> [1] https://lore.kernel.org/linux-ext4/20260203062523.3869120-1-yi.zhang@huawei.com/
> 
> 1. Introduce ext4_block_zero_eof(): Extend and rename
>    ext4_block_truncate_page() to handle post-EOF partial block zeroing
>    for both append writes and truncate operations.
> 2. Separate ordered data handling: Move data=ordered mode handling from
>    __ext4_block_zero_page_range to ext4_block_zero_eof(). Only truncate
>    and post-EOF append write/fallocate paths need ordered data mode,
>    hole punching and zero range paths don't need ordered data handling.
> 3. Split journal mode handling: Extract
>    ext4_block_journalled_zero_range() from
>    __ext4_block_zero_page_range() for data=journal mode, leaving
>    ext4_block_do_zero_range() for data=ordered/writeback modes.
> 4. Refactor ext4_alloc_file_blocks(): Change parameters to loff_t byte
>    granularity to simplify callers and prepares removing the zero call
>    from the allocation loop for unaligned append writes.
> 5. Remove handle parameters: Stop passing handle_t * to zero functions.
>    Make ext4_block_journalled_zero_range() start its own handle, and
>    move zero operations outside active handles. This is required because
>    iomap uses "folio lock -> transaction start" lock ordering, opposite
>    to the current lock ordering.
> 6. Centralize zeroing in ext4_write_checks(): Move all post-EOF partial
>    block zeroing to ext4_write_checks() so it applies to both regular
>    buffered writes and the upcoming iomap path.
> 
> Thanks
> Yi.
> 
> Zhang Yi (10):
>   ext4: add did_zero output parameter to ext4_block_zero_page_range()
>   ext4: ext4_block_truncate_page() returns zeroed length on success
>   ext4: rename and extend ext4_block_truncate_page()
>   ext4: factor out journalled block zeroing range
>   ext4: rename ext4_block_zero_page_range() to ext4_block_zero_range()
>   ext4: move ordered data handling out of ext4_block_do_zero_range()
>   ext4: remove handle parameters from zero partial block functions
>   ext4: pass allocate range as loff_t to ext4_alloc_file_blocks()
>   ext4: move zero partial block range functions out of active handle
>   ext4: zero post-EOF partial block before appending write
> 
>  fs/ext4/ext4.h    |   5 +-
>  fs/ext4/extents.c |  83 +++++++--------
>  fs/ext4/file.c    |  14 +++
>  fs/ext4/inode.c   | 255 ++++++++++++++++++++++++++++------------------
>  4 files changed, 207 insertions(+), 150 deletions(-)
>