Re: [PATCH 3/9] iomap: treat a write through cache the same as FUA

From: Jens Axboe <axboe@kernel.dk>
To: "Darrick J. Wong" <djwong@kernel.org>
Cc: io-uring@vger.kernel.org, linux-xfs@vger.kernel.org, hch@lst.de,
	andres@anarazel.de, david@fromorbit.com
Subject: Re: [PATCH 3/9] iomap: treat a write through cache the same as FUA
Date: Fri, 21 Jul 2023 10:27:16 -0600	[thread overview]
Message-ID: <4fcc44be-f2da-9a7c-03ca-f7e38ac147cb@kernel.dk> (raw)
In-Reply-To: <20230721162553.GS11352@frogsfrogsfrogs>

On 7/21/23 10:25?AM, Darrick J. Wong wrote:
>> @@ -560,12 +562,15 @@ __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
>>  
>>  		       /*
>>  			* For datasync only writes, we optimistically try
>> -			* using FUA for this IO.  Any non-FUA write that
>> -			* occurs will clear this flag, hence we know before
>> -			* completion whether a cache flush is necessary.
>> +			* using WRITE_THROUGH for this IO. Stable writes are
> 
> "...using WRITE_THROUGH for this IO.  This flag requires either FUA
> writes through the device's write cache, or a normal write..."
> 
>> @@ -627,10 +632,10 @@ __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
>>  		iomap_dio_set_error(dio, ret);
>>  
>>  	/*
>> -	 * If all the writes we issued were FUA, we don't need to flush the
>> +	 * If all the writes we issued were stable, we don't need to flush the
> 
> "If all the writes we issued were already written through to the media,
> we don't need to flush..."
> 
> With those fixes,
> Reviewed-by: Darrick J. Wong <djwong@kernel.org>

If you're queueing up this series, could you just make those two edits
while applying? I don't want to spam resend with just a comment change,
at least if I can avoid it...

-- 
Jens Axboe