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Date: Sat, 4 Apr 2015 06:20:05 +0100
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <ming.lei@canonical.com>, Jens Axboe <axboe@fb.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Maxim Patlasov <mpatlasov@parallels.com>
Subject: Re: [PATCH 0/3] block: loop: switch to VFS ITER_BVEC
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On Wed, Mar 25, 2015 at 04:27:48PM +0100, Christoph Hellwig wrote:
> On Wed, Mar 25, 2015 at 03:23:48PM +0800, Ming Lei wrote:
> > > -       mm_segment_t old_fs = get_fs();
> > > +
> > > +       iov_iter_bvec(&i, ITER_BVEC, bvec, 1, bvec->bv_len);
> > >
> > >         file_start_write(file);
> > > -       set_fs(get_ds());
> > > -       bw = file->f_op->write(file, buf, len, &pos);
> > > -       set_fs(old_fs);
> > > +       bw = vfs_iter_write(file, &i, ppos);
> > 
> > This patch moves to support ->read_iter/->write_iter only, which
> > might cause regression for backing file without defining read/write
> > iter callback.
> 
> ->read_iter/->write_iter is the main fs I/O path - by the time this is
> ready ->aio_read/->aio_write should be gone.

	So they are.  Folks, could you base /dev/loop stuff on current
vfs.git#for-next?  And yes, everything that might serve as backing file
for /dev/loop has ->write_iter() now.