Re: [Patch] vectored aio: IO_CMD_P{READ,WRITE}V and fops->aio_{read,write}v

[Christoph Hellwig <hch@lst.de>]

On Wed, Nov 02, 2005 at 03:27:29PM -0800, Zach Brown wrote:
> 
> vectored aio: IO_CMD_P{READ,WRITE}V and fops->aio_{read,write}v
> 
> This adds IO_CMD_IO_CMD_P{READ,WRITE}V to let userspace specify buffers with
> iovecs.  aio_{read,write}v file operations are then used by the AIO core to
> hand the iovecs to filesystems, a significant number of whom already implement
> their IO methods in terms of iovecs.  It lets applications work with vectored
> file IO in single AIO operations instead of having to issue multiple AIO ops.
> This is of particular use with O_DIRECT when the iovecs are pushed all the way
> down to devices which are capable of scatter-gather DMA.

The aio.c portion looks nice.  I'm not happy about the filesystems bits.
The last thing we want is another set of read/write file operations.  So
as part of the patch (it'll probably grow into a series) we should
remove the aio non-vectored and maybe even the plain vectored
operations.  Doing that will be a lot simpler after I finished sorting
out various bits of duplication in the generic read/write path.  I've
sent the first patch for that to -fsdevel already, but there's a few
more to follow.