linux-kernel - Re: [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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Message-ID: <87ttk0d2ck.fsf@debian-BULLSEYE-live-builder-AMD64>
Date: Wed, 17 Apr 2024 10:12:10 +0530
From: Chandan Babu R <chandanbabu@...nel.org>
To: Zhang Yi <yi.zhang@...weicloud.com>
Cc: linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
 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, chengzhihao1@...wei.com, yukuai3@...wei.com
Subject: Re: [PATCH v4 0/9] xfs/iomap: fix non-atomic clone operation and
 don't update size when zeroing range post eof

On Wed, Mar 20, 2024 at 07:05:39 PM +0800, Zhang Yi wrote:
> 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
>

Hi all,

I have picked up this patchset for inclusion into XFS' 6.10-rc1 patch
queue. Please let me know if there are any objections.

-- 
Chandan