linux-ext4 - Re: [RFC PATCH v4 07/11] fs: statx add write zeroes unmap attribute

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Message-ID: <64c8b62a-83ba-45be-a83e-62b6ad8d6f22@huaweicloud.com>
Date: Tue, 6 May 2025 19:16:56 +0800
From: Zhang Yi <yi.zhang@...weicloud.com>
To: Christoph Hellwig <hch@....de>, "Darrick J. Wong" <djwong@...nel.org>
Cc: linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
 linux-block@...r.kernel.org, dm-devel@...ts.linux.dev,
 linux-nvme@...ts.infradead.org, linux-scsi@...r.kernel.org,
 linux-xfs@...r.kernel.org, linux-kernel@...r.kernel.org, tytso@....edu,
 john.g.garry@...cle.com, bmarzins@...hat.com, chaitanyak@...dia.com,
 shinichiro.kawasaki@....com, brauner@...nel.org, yi.zhang@...wei.com,
 chengzhihao1@...wei.com, yukuai3@...wei.com, yangerkun@...wei.com
Subject: Re: [RFC PATCH v4 07/11] fs: statx add write zeroes unmap attribute

On 2025/5/6 12:39, Christoph Hellwig wrote:
> On Tue, May 06, 2025 at 12:28:54PM +0800, Zhang Yi wrote:
>> OK, since this statx reporting flag is not strongly tied to
>> FALLOC_FL_WRITE_ZEROES in vfs_fallocate(), I'll split this patch into
>> three separate patches.
> 
> I don't think that is the right thing to do do.  Keep the flag addition
> here, and then report it in the ext4 and bdev patches adding
> FALLOC_FL_WRITE_ZEROES as the reporting should be consistent with
> the added support.
> 

Sorry, but I don't understand your suggestion. The
STATX_ATTR_WRITE_ZEROES_UNMAP attribute only indicate whether the bdev
and the block device that under the specified file support unmap write
zeroes commoand. It does not reflect whether the bdev and the
filesystems support FALLOC_FL_WRITE_ZEROES. The implementation of
FALLOC_FL_WRITE_ZEROES doesn't fully rely on the unmap write zeroes
commoand now, users simply refer to this attribute flag to determine
whether to use FALLOC_FL_WRITE_ZEROES when preallocating a file.
So, STATX_ATTR_WRITE_ZEROES_UNMAP and FALLOC_FL_WRITE_ZEROES doesn't
have strong relations, why do you suggested to put this into the ext4
and bdev patches that adding FALLOC_FL_WRITE_ZEROES?

Thanks,
Yi.