From: Michal Hocko <mhocko@kernel.org>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Mel Gorman <mgorman@techsingularity.net>,
Johannes Weiner <hannes@cmpxchg.org>,
linux-block@vger.kernel.org, nbd-general@lists.sourceforge.net,
open-iscsi@googlegroups.com, linux-scsi@vger.kernel.org,
netdev@vger.kernel.org, stable@vger.kernel.org,
Andrey Ryabinin <aryabinin@virtuozzo.com>
Subject: Re: [PATCH 1/4] mm: prevent potential recursive reclaim due to clearing PF_MEMALLOC
Date: Wed, 5 Apr 2017 13:21:04 +0200 [thread overview]
Message-ID: <20170405112104.GJ6035@dhcp22.suse.cz> (raw)
In-Reply-To: <20170405074700.29871-2-vbabka@suse.cz>
On Wed 05-04-17 09:46:57, Vlastimil Babka wrote:
> The function __alloc_pages_direct_compact() sets PF_MEMALLOC to prevent
> deadlock during page migration by lock_page() (see the comment in
> __unmap_and_move()). Then it unconditionally clears the flag, which can clear a
> pre-existing PF_MEMALLOC flag and result in recursive reclaim. This was not a
> problem until commit a8161d1ed609 ("mm, page_alloc: restructure direct
> compaction handling in slowpath"), because direct compation was called only
> after direct reclaim, which was skipped when PF_MEMALLOC flag was set.
>
> Even now it's only a theoretical issue, as the new callsite of
> __alloc_pages_direct_compact() is reached only for costly orders and when
> gfp_pfmemalloc_allowed() is true, which means either __GFP_NOMEMALLOC is in
> gfp_flags or in_interrupt() is true. There is no such known context, but let's
> play it safe and make __alloc_pages_direct_compact() robust for cases where
> PF_MEMALLOC is already set.
>
> Fixes: a8161d1ed609 ("mm, page_alloc: restructure direct compaction handling in slowpath")
> Reported-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
> Cc: <stable@vger.kernel.org>
Acked-by: Michal Hocko <mhocko@suse.com>
> ---
> mm/page_alloc.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 3589f8be53be..b84e6ffbe756 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -3288,6 +3288,7 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
> enum compact_priority prio, enum compact_result *compact_result)
> {
> struct page *page;
> + unsigned int noreclaim_flag = current->flags & PF_MEMALLOC;
>
> if (!order)
> return NULL;
> @@ -3295,7 +3296,7 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
> current->flags |= PF_MEMALLOC;
> *compact_result = try_to_compact_pages(gfp_mask, order, alloc_flags, ac,
> prio);
> - current->flags &= ~PF_MEMALLOC;
> + current->flags = (current->flags & ~PF_MEMALLOC) | noreclaim_flag;
>
> if (*compact_result <= COMPACT_INACTIVE)
> return NULL;
> --
> 2.12.2
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2017-04-05 11:21 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-05 7:46 [PATCH 0/4] more robust PF_MEMALLOC handling Vlastimil Babka
2017-04-05 7:46 ` [PATCH 1/4] mm: prevent potential recursive reclaim due to clearing PF_MEMALLOC Vlastimil Babka
2017-04-05 11:21 ` Michal Hocko [this message]
2017-04-05 11:40 ` Andrey Ryabinin
2017-04-07 9:21 ` Vlastimil Babka
2017-04-07 7:33 ` Hillf Danton
2017-04-05 7:46 ` [PATCH 2/4] mm: introduce memalloc_noreclaim_{save,restore} Vlastimil Babka
2017-04-05 11:28 ` Michal Hocko
2017-04-07 7:38 ` Hillf Danton
2017-04-05 7:46 ` [PATCH 3/4] treewide: convert PF_MEMALLOC manipulations to new helpers Vlastimil Babka
2017-04-05 11:30 ` Michal Hocko
2017-04-06 6:38 ` [Nbd] " Wouter Verhelst
2017-04-06 11:25 ` Mel Gorman
2017-04-05 7:47 ` [PATCH 4/4] mtd: nand: nandsim: convert to memalloc_noreclaim_*() Vlastimil Babka
2017-04-05 11:31 ` Michal Hocko
2017-04-05 11:36 ` Richard Weinberger
2017-04-05 11:39 ` Vlastimil Babka
2017-04-05 12:09 ` Michal Hocko
2017-04-06 6:33 ` Adrian Hunter
2017-04-06 7:27 ` Michal Hocko
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=20170405112104.GJ6035@dhcp22.suse.cz \
--to=mhocko@kernel.org \
--cc=akpm@linux-foundation.org \
--cc=aryabinin@virtuozzo.com \
--cc=hannes@cmpxchg.org \
--cc=linux-block@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linux-scsi@vger.kernel.org \
--cc=mgorman@techsingularity.net \
--cc=nbd-general@lists.sourceforge.net \
--cc=netdev@vger.kernel.org \
--cc=open-iscsi@googlegroups.com \
--cc=stable@vger.kernel.org \
--cc=vbabka@suse.cz \
/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
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).