[PATCH v3 0/3] xfs: clean up directory data block header padding

[Yuto Ohnuki <ytohnuki@amazon.com>]

The pad field in xfs_dir3_data_hdr exists for 64-bit alignment and 
should always be zero. Old kernels zeroed only the xfs_dir3_blk_hdr 
portion of the header during initialization and initialized the 
remaining header contents separately.

This series takes a broader approach as suggested by Dave Chinner:
zero the entire header region unconditionally, self-heal stale non-zero
padding during writes, and report remaining non-zero padding in scrub.

Patch 1 zeroes the entire directory data block header region in
xfs_dir3_data_init instead of just the xfs_dir3_blk_hdr.
Patch 2 zeroes the pad field in xfs_dir3_data_write_verify so that
existing directories self-heal when modified.
Patch 3 checks the pad field in scrub and adds xchk_fblock_set_preen.

Changes in v3:
- Zero the entire header region (geo->data_entry_offset bytes)
  unconditionally instead of changing the memset type to
  xfs_dir3_data_hdr.
- Remove the now-unnecessary bestfree manual zeroing loop.
- Zero pad in xfs_dir3_data_write_verify for runtime self-healing
  of old metadata.
- Drop unnecessary cpu_to_be32() on comparison to zero.
- Split into a 3-patch series for easier review.
- Link to v2: https://lore.kernel.org/all/20260408172749.99216-2-ytohnuki@amazon.com/#t

Changes in v2:
- Fix xfs_dir3_data_init to zero the full xfs_dir3_data_hdr instead of
  just xfs_dir3_blk_hdr so that the pad field is covered by the memset.
- Use xchk_fblock_set_preen instead of xchk_fblock_set_corrupt since
  old kernels may have written non-zero padding without issues.
- Add xchk_fblock_set_preen helper function.
- Link to v1: https://lore.kernel.org/all/20260404125032.37693-2-ytohnuki@amazon.com/#t

Yuto Ohnuki (3):
  xfs: zero entire directory data block header region at init
  xfs: zero directory data block padding on write verification
  xfs: check directory data block header padding in scrub

 fs/xfs/libxfs/xfs_dir2_data.c | 18 +++++++++++-------
 fs/xfs/scrub/common.c         | 11 +++++++++++
 fs/xfs/scrub/common.h         |  2 ++
 fs/xfs/scrub/dir.c            |  7 ++++++-
 4 files changed, 30 insertions(+), 8 deletions(-)

-- 
2.50.1




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