linux-kernel - Re: [PATCH v6 03/13] iomap: rework IOMAP atomic flags

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Message-ID: <87cf27a2-6bbb-4073-b150-c4d07e382032@oracle.com>
Date: Mon, 17 Mar 2025 09:05:39 +0000
From: John Garry <john.g.garry@...cle.com>
To: Christoph Hellwig <hch@....de>
Cc: brauner@...nel.org, djwong@...nel.org, cem@...nel.org, dchinner@...hat.com,
        linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, ojaswin@...ux.ibm.com,
        ritesh.list@...il.com, martin.petersen@...cle.com, tytso@....edu,
        linux-ext4@...r.kernel.org
Subject: Re: [PATCH v6 03/13] iomap: rework IOMAP atomic flags

On 17/03/2025 06:11, Christoph Hellwig wrote:
>>   		iomap->flags |= IOMAP_F_NEW;
>>   
>> +	if (flags & IOMAP_ATOMIC)
>> +		iomap->flags |= IOMAP_F_ATOMIC_BIO;
>> +
> 
> Add a comment here that ext4 is always using hardware atomics?
> 
>> +	if (flags & IOMAP_ATOMIC)
>> +		iomap_flags |= IOMAP_F_ATOMIC_BIO;
> 
> Same here (at least for now until it is changed later).

Please note that Christian plans on sending the earlier iomap changes 
related to this work for 6.15. Those changes are also in the xfs queue. 
We are kinda reverting those changes here, so I think that it would 
still make sense for the iomap changes in this series to make 6.15

The xfs changes in this series are unlikely to make 6.15

As such, if we say that ext4 always uses hardware atomics, then we 
should mention that xfs does also (until it doesn't).

So, in the end, I'd rather not add those comments at all - ok?

> 
>> + * IOMAP_F_ATOMIC_BIO indicates that (write) I/O needs to be issued as an
>> + * atomic bio, i.e. set REQ_ATOMIC.
> 
> s/needs to/will be/ ?
> 
ok