linux-kernel - [PATCH v4 0/9] xfs/iomap: fix non-atomic clone operation and don't update size when zeroing range post eof

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Date: Wed, 20 Mar 2024 19:05:39 +0800
From: Zhang Yi <yi.zhang@...weicloud.com>
To: linux-xfs@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
	djwong@...nel.org,
	hch@...radead.org,
	brauner@...nel.org,
	david@...morbit.com,
	tytso@....edu,
	jack@...e.cz,
	yi.zhang@...wei.com,
	yi.zhang@...weicloud.com,
	chengzhihao1@...wei.com,
	yukuai3@...wei.com
Subject: [PATCH v4 0/9] xfs/iomap: fix non-atomic clone operation and don't update size when zeroing range post eof

Changes since v3:
 - Improve some git message comments and do some minor code cleanup, no
   logic changes.

Changes since v2:
 - Merge the patch for dropping of xfs_convert_blocks() and the patch
   for modifying xfs_bmapi_convert_delalloc().
 - Reword the commit message of the second patch.

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 (9):
  xfs: match lock mode in xfs_buffered_write_iomap_begin()
  xfs: make the seq argument to xfs_bmapi_convert_delalloc() optional
  xfs: make xfs_bmapi_convert_delalloc() to allocate the target offset
  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 iomap_write_end() return a boolean
  iomap: do some small logical cleanup in buffered write

 fs/iomap/buffered-io.c   | 105 ++++++++++++++++++++++-----------------
 fs/xfs/libxfs/xfs_bmap.c |  40 +++++++++++++--
 fs/xfs/xfs_aops.c        |  54 ++++++--------------
 fs/xfs/xfs_iomap.c       |  39 +++++++++++++--
 4 files changed, 144 insertions(+), 94 deletions(-)

-- 
2.39.2