From: Matthew Wilcox <[email protected]>
To: Jens Axboe <[email protected]>
Cc: [email protected], [email protected],
[email protected], [email protected]
Subject: Re: [PATCH 0/2] Close a hole where IOCB_NOWAIT reads could sleep
Date: Sat, 24 Jul 2021 19:22:20 +0100 [thread overview]
Message-ID: <YPxaXE0mf26aqy/[email protected]> (raw)
In-Reply-To: <[email protected]>
On Sun, Jul 11, 2021 at 07:44:07PM -0600, Jens Axboe wrote:
> On 7/11/21 9:09 AM, Matthew Wilcox (Oracle) wrote:
> > I noticed a theoretical case where an IOCB_NOWAIT read could sleep:
> >
> > filemap_get_pages
> > filemap_get_read_batch
> > page_cache_sync_readahead
> > page_cache_sync_ra
> > ondemand_readahead
> > do_page_cache_ra
> > page_cache_ra_unbounded
> > gfp_t gfp_mask = readahead_gfp_mask(mapping);
> > memalloc_nofs_save()
> > __page_cache_alloc(gfp_mask);
> >
> > We're in a nofs context, so we're not going to start new IO, but we might
> > wait for writeback to complete. We generally don't want to sleep for IO,
> > particularly not for IO that isn't related to us.
> >
> > Jens, can you run this through your test rig and see if it makes any
> > practical difference?
>
> You bet, I'll see if I can trigger this condition and verify we're no
> longer blocking on writeback. Thanks for hacking this up.
Did you have any success yet?
next prev parent reply other threads:[~2021-07-24 18:22 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-11 15:09 [PATCH 0/2] Close a hole where IOCB_NOWAIT reads could sleep Matthew Wilcox (Oracle)
2021-07-11 15:09 ` [PATCH 1/2] mm/readahead: Add gfp_flags to ractl Matthew Wilcox (Oracle)
2021-07-12 11:34 ` Christoph Hellwig
2021-07-12 14:37 ` Matthew Wilcox
2021-07-11 15:09 ` [PATCH 2/2] mm/filemap: Prevent waiting for memory for NOWAIT reads Matthew Wilcox (Oracle)
2021-07-12 1:44 ` [PATCH 0/2] Close a hole where IOCB_NOWAIT reads could sleep Jens Axboe
2021-07-24 18:22 ` Matthew Wilcox [this message]
2021-07-24 19:46 ` Jens Axboe
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