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

[Zhang Yi]

From: Zhang Yi <yi.zhang@xxxxxxxxxx>

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@xxxxxxxxxxxxxxx/

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@xxxxxxxxxx/

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(-)

-- 
2.52.0