linux-kernel - Re: [PATCH v6 10/13] xfs: iomap COW-based atomic write support

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Message-ID: <aad48c97-20dc-4fec-aeda-9f87294bac78@oracle.com>
Date: Mon, 17 Mar 2025 14:56:52 +0000
From: John Garry <john.g.garry@...cle.com>
To: "Ritesh Harjani (IBM)" <ritesh.list@...il.com>, brauner@...nel.org,
        djwong@...nel.org, cem@...nel.org, dchinner@...hat.com, hch@....de
Cc: linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, ojaswin@...ux.ibm.com,
        martin.petersen@...cle.com, tytso@....edu, linux-ext4@...r.kernel.org
Subject: Re: [PATCH v6 10/13] xfs: iomap COW-based atomic write support

On 17/03/2025 14:20, Ritesh Harjani (IBM) wrote:
>> And, as mentioned earlier, it is ok to use REQ_ATOMIC method on an
>> unwritten extent.
>>
>>> I am guessing this is kept intentional?
>>>
>> Yes
> Thanks, John for addressing the queries. It would be helpful to include
> this information in the commit message as well then right? Otherwise
> IMO, the original commit message looks incomplete.

ok, fine. I am just worried that these commit messages become too wordy. 
But, if people want this info, then I can provide it.

> 
> Maybe we can add this too?
> =========================
> This patch adds CoW based atomic write support which will be used as a
> SW fallback in following scenarios:
> 
> - All append write scenarios.
> - Any new writes on the region containing holes.

but only for > 1x block.

if we must be able to alloc at least a block :)

> - Writes to any misaligned regions
> - Writes to discontiguous extents.

ok, fine

> 
> 
> <original commit msg snip>
> =========================
> In cases of an atomic write covering misaligned or discontiguous disk
> blocks, we will use a CoW-based method to issue the atomic write.

sure

Thanks,
John