All of lore.kernel.org
 help / color / mirror / Atom feed
From: Zhaoyang Huang <huangzhaoyang@gmail.com>
To: David Howells <dhowells@redhat.com>
Cc: Marc Dionne <marc.dionne@auristor.com>,
	Zhaoyang Huang <zhaoyang.huang@unisoc.com>,
	linux-cachefs@redhat.com, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] fs: judging context via current_is_kswapd instead of gfp_flag
Date: Wed, 22 Dec 2021 16:02:18 +0800	[thread overview]
Message-ID: <CAGWkznGgyS5VrcuYkWR_7sbDOkr0k2mDNUwF6F6N-Y_3GGtoJA@mail.gmail.com> (raw)
In-Reply-To: <73896.1640098820@warthog.procyon.org.uk>

On Tue, Dec 21, 2021 at 11:01 PM David Howells <dhowells@redhat.com> wrote:
>
> Zhaoyang Huang <huangzhaoyang@gmail.com> wrote:
>
> > > > -             if (!(gfp_flags & __GFP_DIRECT_RECLAIM) || !(gfp_flags & __GFP_FS))
> > > > +             if (current_is_kswapd() || !(gfp_flags & __GFP_FS))
> > > >                       return false;
> > > >               wait_on_page_fscache(page);
> > ...
> > If the gfp flag here is used for judging kswapd context, I think the
> > answer is yes as kswapd applied __GFP_DIRECT_RECLAIM.
>
> Now I come to look at applying it, I'm not sure whether this change is right.
>
> I don't know if kswapd has anything to do with it.  The check is to see if
> we're allowed to block at this point - and wait is just for the completion of
> a DIO write to disk.
>
> It would seem like gfpflags_allow_blocking() is the right thing to call - and
> that should use current_is_kswapd() if appropriate.
>
> David
According to my understanding, this check is redundant according to
current vmscan logic. For the allocation which deny
__GFP_DIRECT_RECLAIM could NOT have the context reach here as there is
no synchronous reclaiming. while kswapd also has __GFP_DIRECT_RECLAIM
set and would also block on the page's release.
>

      reply	other threads:[~2021-12-22  8:02 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-08  8:37 Huangzhaoyang
2021-12-08 20:26 ` David Howells
2021-12-10  1:19   ` Zhaoyang Huang
2021-12-21 15:00   ` David Howells
2021-12-22  8:02     ` Zhaoyang Huang [this message]

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=CAGWkznGgyS5VrcuYkWR_7sbDOkr0k2mDNUwF6F6N-Y_3GGtoJA@mail.gmail.com \
    --to=huangzhaoyang@gmail.com \
    --cc=dhowells@redhat.com \
    --cc=linux-cachefs@redhat.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=marc.dionne@auristor.com \
    --cc=zhaoyang.huang@unisoc.com \
    --subject='Re: [PATCH] fs: judging context via current_is_kswapd instead of gfp_flag' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.