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

[Jan Kara <jack@suse.cz>]

On Mon 14-10-19 19:52:18, Matthew Bobrowski wrote:
> 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? :)

No, go ahead. Thanks!

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR