[v3,00/10] ext4: clean up and refactor fallocate

Message

Zhang Yi Oct. 10, 2024, 1:33 p.m. UTC

Changes since v2:
 - Add Patch 1 to address a newly discovered data loss issue that occurs
   when using mmap to write after zeroing out a partial page on a
   filesystem with the block size smaller than the page size.
 - Do not write all data before punching hole, zeroing out and
   collapsing range as Jan suggested, also drop current data writeback
   in ext4_punch_hole().
 - Since we don't write back all data in these 4 operations, we only
   writeback data during inserting range,so do not factor out new
   helpers in the last two patches, just move common components of
   sub-operations into ext4_fallocate().
 - Only keep Jan's review tag on patch 02 and 08, other patches contain
   many code adaptations since v2, so please review them again.
Changes since v1:
 - Fix an using uninitialized variable problem in the error out path in
   ext4_do_fallocate() in patch 08.

v2: https://lore.kernel.org/linux-ext4/[e-mail]/

Current ext4 fallocate code is mess with mode checking, locking, input
parameter checking, position calculation, and having some stale code.
Almost all five sub-operation share similar preparation steps, so it
deserves a cleanup now.

This series tries to improve the code by refactoring all operations
related to fallocate. It unifies variable naming, reduces unnecessary
position calculations, and factors out common preparation components.

The first patch addresses a potential data loss issue that occurs when
using mmap to write after zeroing out partial blocks of a page on a
filesystem where the block size is smaller than the page size.
Subsequent patches focus on cleanup and refactoring, please see them for
details. After this series, we will significantly reduce redundant code
and enhance clarity compared to the previous version.

Thanks,
Yi.


Zhang Yi (10):
  ext4: remove writable userspace mappings before truncating page cache
  ext4: don't explicit update times in ext4_fallocate()
  ext4: don't write back data before punch hole in nojournal mode
  ext4: refactor ext4_punch_hole()
  ext4: refactor ext4_zero_range()
  ext4: refactor ext4_collapse_range()
  ext4: refactor ext4_insert_range()
  ext4: factor out ext4_do_fallocate()
  ext4: move out inode_lock into ext4_fallocate()
  ext4: move out common parts into ext4_fallocate()

 fs/ext4/ext4.h    |   2 +
 fs/ext4/extents.c | 532 ++++++++++++++++++----------------------------
 fs/ext4/inode.c   | 188 ++++++++--------
 3 files changed, 303 insertions(+), 419 deletions(-)