Re: [PATCH 05/15] mm: allow read-ahead with IOCB_NOWAIT set

[Matthew Wilcox]

On Wed, Jun 24, 2020 at 09:35:19AM -0600, Jens Axboe wrote:
> On 6/24/20 9:00 AM, Jens Axboe wrote:
> > On 6/23/20 7:46 PM, Matthew Wilcox wrote:
> >> I'd be quite happy to add a gfp_t to struct readahead_control.
> >> The other thing I've been looking into for other reasons is adding
> >> a memalloc_nowait_{save,restore}, which would avoid passing down
> >> the gfp_t.
> > 
> > That was my first thought, having the memalloc_foo_save/restore for
> > this. I don't think adding a gfp_t to readahead_control is going
> > to be super useful, seems like the kind of thing that should be
> > non-blocking by default.
> 
> We're already doing memalloc_nofs_save/restore in
> page_cache_readahead_unbounded(), so I think all we need is to just do a
> noio dance in generic_file_buffered_read() and that should be enough.

I think we can still sleep though, right?  I was thinking more
like this:

http://git.infradead.org/users/willy/linux.git/shortlog/refs/heads/memalloc