linux-ext4 - Re: [RFC v2 0/2] ext4: Add multi-fsblock atomic write support using bigalloc

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Message-ID: <d031d255-b528-4870-b933-475b969aabdf@oracle.com>
Date: Thu, 8 May 2025 13:01:33 +0100
From: John Garry <john.g.garry@...cle.com>
To: "Ritesh Harjani (IBM)" <ritesh.list@...il.com>,
        Theodore Ts'o <tytso@....edu>, Jan Kara <jack@...e.cz>
Cc: djwong@...nel.org, Ojaswin Mujoo <ojaswin@...ux.ibm.com>,
        linux-ext4@...r.kernel.org
Subject: Re: [RFC v2 0/2] ext4: Add multi-fsblock atomic write support using
 bigalloc

On 30/04/2025 06:20, Ritesh Harjani (IBM) wrote:
> This is still an early preview (RFC v2) of multi-fsblock atomic write. Since the
> core design of the feature looks ready, wanted to post this for some early
> feedback. We will break this into more smaller and meaningful patches in later
> revision. However to simplify the review of the core design changes, this
> version is limited to just two patches. Individual patches might have more
> details in the commit msg.
> 
> Note: This overall needs more careful review (other than the core design) which
> I will be doing in parallel. However it would be helpful if one can provide any
> feedback on the core design changes. Specially around ext4_iomap_alloc()
> changes, ->end_io() changes and a new get block flag
> EXT4_GET_BLOCKS_QUERY_LEAF_BLOCKS.

I gave this a try and it looks ok, specifically atomic writing mixed 
mappings.

I'll try to look closer that the implementation details. But I do note 
that you use blkdev_issue_zeroout() to pre-zero any unwritten range 
which is being atomically written.