Re: [PATCH v4 2/3] NFSD: Implement NFSD_IO_DIRECT for NFS WRITE

[Chuck Lever <cel@kernel.org>]

On 10/20/25 3:19 AM, Christoph Hellwig wrote:
>> +	/*
>> +	 * Any buffered IO issued here will be misaligned, use
>> +	 * sync IO to ensure it has completed before returning.
>> +	 * Also update @stable_how to avoid need for COMMIT.
>> +	 */
>> +	kiocb->ki_flags |= (IOCB_DSYNC | IOCB_SYNC);
> What do you mean with completed before returning?  I guess you
> mean writeback actually happening, right?  Why do you need that,
> why do you also force it for the direct I/O?

This is the only comment where I'm not clear on what corrective
action to take.

I think IOCB_SYNC would be needed with O_DIRECT to force timestamp
updates. Otherwise, IOCB_SYNC is relevant only when the function is
forced to fall back to some form of write through the page cache.

Is that correct?


-- 
Chuck Lever