[PATCH v2 00/10] xfs/iomap: fix non-atomic clone operation and don't update size when zeroing range post eof

Zhang Yi
2024-03-15T13:01:07Z

Changes since v1:
- Make xfs_bmapi_convert_delalloc() to allocate the target offset and
drop the writeback helper xfs_convert_blocks().
- Don't use xfs_iomap_write_direct() to convert delalloc blocks for
zeroing posteof case, use xfs_bmapi_convert_delalloc() instead.
- Fix two off-by-one issues when converting delalloc blocks.
- Add a separate patch to drop the buffered write failure handle in
zeroing and unsharing.
- Add a comments do emphasize updating i_size should under folio lock.
- Make iomap_write_end() to return a boolean, and do some cleanups in
buffered write begin path.

This patch series fix a problem of exposing zeroed data on xfs since the
non-atomic clone operation. This problem was found while I was
developing ext4 buffered IO iomap conversion (ext4 is relying on this
fix [1]), the root cause of this problem and the discussion about the
solution please see [2]. After fix the problem, iomap_zero_range()
doesn't need to update i_size so that ext4 can use it to zero partial
block, e.g. truncate eof block [3].

[1] https://lore.kernel.org/linux-ext4/20240127015825.1608160-1-yi.zhang@huaweicloud.com/
[2] https://lore.kernel.org/linux-ext4/9b0040ef-3d9d-6246-4bdd-82b9a8f55fa2@huaweicloud.com/
[3] https://lore.kernel.org/linux-ext4/9c9f1831-a772-299b-072b-1c8116c3fb35@huaweicloud.com/

Thanks,
Yi.

Zhang Yi (10):
xfs: match lock mode in xfs_buffered_write_iomap_begin()
xfs: allow xfs_bmapi_convert_delalloc() to pass NULL seq
xfs: make xfs_bmapi_convert_delalloc() to allocate the target offset
xfs: drop xfs_convert_blocks()
xfs: convert delayed extents to unwritten when zeroing post eof blocks
iomap: drop the write failure handles when unsharing and zeroing
iomap: don't increase i_size if it's not a write operation
iomap: use a new variable to handle the written bytes in
iomap_write_iter()
iomap: make block_write_end() return a boolean
iomap: do some small logical cleanup in buffered write

fs/iomap/buffered-io.c | 101 ++++++++++++++++++++++-----------------
fs/xfs/libxfs/xfs_bmap.c | 40 ++++++++++++++--
fs/xfs/xfs_aops.c | 54 ++++++---------------
fs/xfs/xfs_iomap.c | 39 +++++++++++++--
4 files changed, 142 insertions(+), 92 deletions(-)

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2.39.2