On Sun, Jan 04, 2026 at 05:49:13PM +0530, Ojaswin Mujoo wrote:
> Offlate we've have seen multiple issues and inconsistencies in the
> our extent splitting and conversion logic causing subtle bugs. Recent
> patches by Yhang Zi [1] helped address some of the issues however
> the messy use of EXT4_EXT_DATA_VALID* and EXT4_EXT_MARK_UNWRIT* flags
> made the implementation confusing and error prone.
>
> This patchset aims to refactor the explent split and convert code paths
> to make the code simpler and the behavior consistent and easy to
> understand. It also adds several Kunit tests to stress various
> permutations of extent splitting and conversion.
>
> I've rebased this over [2] since it seems like it'll go in first.
>
> Another idea I want to try out after this is proactively zeroout
> before even trying to split, as Jan suggested here [3], but before
> trying to do that I wanted to refactor and add some tests hence sending
> these patches out first.
>
> [1] https://lore.kernel.org/linux-ext4/20251129103247.686136-1-yi.zhang@huaweicloud.com/
> [2] https://lore.kernel.org/linux-ext4/20251223011802.31238-1-yi.zhang@huaweicloud.com/T/#t
> [3] https://lore.kernel.org/linux-ext4/yro4hwpttmy6e2zspvwjfdbpej6qvhlqjvlr5kp3nwffqgcnfd@z6qual55zhfq/
>
> Rest of the details can be found in the commit messages.
>
> Patch 1-2: new kunit tests
> Patch 3-4: minor fixes
> Patch 5: refactoring zeroout and making sure zeroout handles all
> permutations correctly
> Patch 6: Refactoring ext4_split_* functions.
> Patch 7: Enable zeroout for writ to unwrit case
>
> Testing:
> - I've run kvm-xfstests for 4k, 1k and bigalloc_4k with -g quick and I
> see no failures.
> - Some new kunit tests that were failing due to inconsistencies are not
> passing
Are *now* passing with the patches* :)
> - Due to dev servers being down for eoy maintanence I couldn't run more
> rigourous tests. In the coming week I'll run stress and auto group as
> well.
>
> Thoughts and comments are welcome.
>
> Ojaswin Mujoo (7):
> ext4: kunit tests for extent splitting and conversion
> ext4: kunit tests for higher level extent manipulation functions
> ext4: propagate flags to convert_initialized_extent()
> ext4: propagate flags to ext4_convert_unwritten_extents_endio()
> ext4: Refactor zeroout path and handle all cases
> ext4: Refactor split and convert extents
> ext4: Allow zeroout when doing written to unwritten split
>
> fs/ext4/extents-test.c | 871 +++++++++++++++++++++++++++++++++++++++
> fs/ext4/extents.c | 591 +++++++++++++++-----------
> fs/ext4/extents_status.c | 3 +
> fs/ext4/inode.c | 4 +
> 4 files changed, 1226 insertions(+), 243 deletions(-)
> create mode 100644 fs/ext4/extents-test.c
>
> --
> 2.51.0
>