Message-ID: <50AFB373.8020507@oracle.com>
Date: Fri, 23 Nov 2012 11:33:39 -0600
From: Dave Kleikamp <dave.kleikamp@oracle.com>
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To: Christoph Hellwig <hch@infradead.org>
CC: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        Zach Brown <zab@zabbo.net>,
        "Maxim V. Patlasov" <mpatlasov@parallels.com>
Subject: Re: [PATCH v4 00/31] loop: Issue O_DIRECT aio using bio_vec
References: <1353537671-26284-1-git-send-email-dave.kleikamp@oracle.com> <20121122194731.GA12057@infradead.org>
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On 11/22/2012 01:47 PM, Christoph Hellwig wrote:
> On Wed, Nov 21, 2012 at 04:40:40PM -0600, Dave Kleikamp wrote:
>> It introduces new file ops, read_iter() and write_iter(), that replace the
>> aio_read() and aio_write() operations. The iov_iter structure can now contain
>> either a user-space iovec or a kernel-space bio_vec. Since it would be
>> overly complicated to replace every instance of aio_read() and aio_write(),
>> the old operations are not removed, but file systems implementing the new
>> ones need not keep the old ones.
> 
> How many instance of the old ones are left?  I'd really prefer to make
> the full transition very quickly, even if not nessecarily in a single
> patchset.

The only file systems left are ceph, cifs, fuse and ntfs, but there are
the pipe driver and quite a few character devices that implement
aio_read and aio_write. It would be easy enough put a read/write_iter
wrapper around the non-block devices that return an error or even panic
if !iov_iter_has_iovec(iter), but I didn't like the way it looked.

(I think "git grep -e \\\.aio_read -e \\\.aio_write" find them all.)

If the consensus is to go that route, I'd be happy to work on a
follow-up patchset.

Shaggy
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