Re: [vfs:work.aio 10/12] fs/aio.c:1444: undefined reference to `ioprio_check_cap'

From: Steve French <smfrench@gmail.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: Jens Axboe <axboe@kernel.dk>,
	Adam Manzanares <Adam.Manzanares@wdc.com>,
	Christoph Hellwig <hch@lst.de>, Al Viro <viro@zeniv.linux.org.uk>,
	kbuild test robot <lkp@intel.com>,
	"kbuild-all@01.org" <kbuild-all@01.org>,
	"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
	Jeff Moyer <jmoyer@redhat.com>, Steve French <sfrench@samba.org>,
	CIFS <linux-cifs@vger.kernel.org>,
	linux-nfs@vger.kernel.org
Subject: Re: [vfs:work.aio 10/12] fs/aio.c:1444: undefined reference to `ioprio_check_cap'
Date: Fri, 1 Jun 2018 15:31:46 -0500	[thread overview]
Message-ID: <CAH2r5muVt9usKJX0Xmsf3oxYhAu0m8G5VZc8AUb0fh1+h-y3JA@mail.gmail.com> (raw)
In-Reply-To: <20180601172835.GA29651@bombadil.infradead.org>

On Fri, Jun 1, 2018 at 12:28 PM, Matthew Wilcox <willy@infradead.org> wrote:
> On Fri, Jun 01, 2018 at 09:59:03AM -0600, Jens Axboe wrote:
>> On 6/1/18 9:57 AM, Adam Manzanares wrote:
>> >
>> >
>> > On 6/1/18 8:41 AM, Jens Axboe wrote:
>> >> On 6/1/18 9:38 AM, Adam Manzanares wrote:
>> >>> On 5/31/18 10:13 PM, Christoph Hellwig wrote:
>> >>>>> +extern int ioprio_check_cap(int ioprio);
>> >>>>
>> >>>> Which then is implemented in block/ioprio.c, which depends on
>> >>>> CONFIG_BLOCK.  The code either needs a stub for !CONFIG_BLOCK
>> >>>> or moved elsewhere.
>> >>>
>> >>> My vote would be to move the ioprio code into fs/. At first glance I do
>> >>> not see a dependence on the block layer in block/ioprio.c.
>> >>>
>> >>> Any objections?
>> >>
>> >> Since it's block ioprio code, I'd prefer a stub instead.
>> >>
>> >
>> > This feature could be used independently from the block layer. We have
>> > examples (ATA, hopefully NVME soon) where we are reacting to the ioprio
>> > in the device drivers essentially passing the ioprio through the block
>> > layer.
>>
>> It could, yes, but it isn't. As it stands, it's system call support to
>> pass in IO priority for what ultimately is block storage.
>
> I think it'd be interesting if NFS/SMB decided to start using it.
> I think SMB has the concept of io priorities within a single stream ...
> Steve?

Yes - in theory SMB3 does, but I need to research this more to
see if useable here.  Will also discuss with others at SambaXP to see
if ideas from others.  Also note that SMB3 has a per-io flag (for read
and write) that allows "unbuffered" and "writethrough" to be set on
a per operation basis (not just on a per-file handle basis).  Would
be interesting if we could get hints on when to set these flags
on a per-operation basis (rather than just on the handle at
open time).

-- 
Thanks,

Steve