Re: [RFC PATCH v2 04/16] iomap: add async buffered write support

[Jan Kara <jack@suse.cz>]

On Mon 16-05-22 09:47:06, Stefan Roesch wrote:
> This adds async buffered write support to iomap. The support is focused
> on the changes necessary to support XFS with iomap.
> 
> Support for other filesystems might require additional changes.
> 
> Signed-off-by: Stefan Roesch <shr@fb.com>
> ---
>  fs/iomap/buffered-io.c | 21 ++++++++++++++++++++-
>  1 file changed, 20 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index 1ffdc7078e7d..ceb3091f94c2 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -580,13 +580,20 @@ static int __iomap_write_begin(const struct iomap_iter *iter, loff_t pos,
>  	size_t from = offset_in_folio(folio, pos), to = from + len;
>  	size_t poff, plen;
>  	gfp_t  gfp = GFP_NOFS | __GFP_NOFAIL;
> +	bool no_wait = (iter->flags & IOMAP_NOWAIT);
> +
> +	if (no_wait)
> +		gfp = GFP_NOIO;

GFP_NOIO means that direct reclaim is still allowed. Not sure whether you
want to enter direct reclaim from io_uring fast path because in theory that
can still sleep. GFP_NOWAIT would be a more natural choice...

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