Re: [PATCH 0/2 v3] iomap: Waiting for IO in iomap_dio_rw()

[Matthew Bobrowski <mbobrowski@mbobrowski.org>]

On Mon, Oct 14, 2019 at 10:26:01AM +0200, Jan Kara wrote:
> Original motivation:
> 
> when doing the ext4 conversion of direct IO code to iomap, we found it very
> difficult to handle inode extension with what iomap code currently provides.
> Ext4 wants to do inode extension as sync IO (so that the whole duration of
> IO is protected by inode->i_rwsem), also we need to truncate blocks beyond
> end of file in case of error or short write. Now in ->end_io handler we don't
> have the information how long originally the write was (to judge whether we
> may have allocated more blocks than we actually used) and in ->write_iter
> we don't know whether / how much of the IO actually succeeded in case of AIO.
> 
> Thinking about it for some time I think iomap code makes it unnecessarily
> complex for the filesystem in case it decides it doesn't want to perform AIO
> and wants to fall back to good old synchronous IO. In such case it is much
> easier for the filesystem if it just gets normal error return from
> iomap_dio_rw() and not just -EIOCBQUEUED.
> 
> The first patch in the series adds argument to iomap_dio_rw() to wait for IO
> completion (internally iomap_dio_rw() already supports this!) and the second
> patch converts XFS waiting for unaligned DIO write to this new API.

Ah, wonderful, I was waiting for this to come through.

I'll rebase my EXT4 direct I/O port on top of these patches and apply
the discussed changes. Any objections? :)

--<M>--