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From: Sasha Levin <sasha.levin@oracle.com>
To: Wanpeng Li <liwanp@linux.vnet.ibm.com>,
	Andrew Morton <akpm@linux-foundation.org>
Cc: Michel Lespinasse <walken@google.com>,
	Bob Liu <bob.liu@oracle.com>,
	npiggin@suse.de, kosaki.motohiro@jp.fujitsu.com, riel@redhat.com,
	David Rientjes <rientjes@google.com>,
	Mel Gorman <mgorman@suse.de>, Minchan Kim <minchan@kernel.org>,
	Vlastimil Babka <vbabka@suse.cz>, Hugh Dickins <hughd@google.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm/mlock: fix BUG_ON unlocked page for nolinear VMAs
Date: Tue, 17 Dec 2013 22:32:53 -0500	[thread overview]
Message-ID: <52B11765.8030005@oracle.com> (raw)
In-Reply-To: <20131218032329.GA6044@hacker.(null)>

On 12/17/2013 10:23 PM, Wanpeng Li wrote:
> -			mlock_vma_page(page);   /* no-op if already mlocked */
> -			if (page == check_page)
> +			if (page != check_page && trylock_page(page)) {
> +				mlock_vma_page(page);   /* no-op if already mlocked */
> +				unlock_page(page);
> +			} else if (page == check_page) {
> +				mlock_vma_page(page);  /* no-op if already mlocked */
>   				ret = SWAP_MLOCK;
> +			}

Previously, if page != check_page and the page was locked, we'd call mlock_vma_page()
anyways. With this change, we don't. In fact, we'll just skip that entire block not doing
anything.

If that's something that's never supposed to happen, can we add a

	VM_BUG_ON(page != check_page && PageLocked(page))

Just to cover this new code path?


Thanks,
Sasha

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WARNING: multiple messages have this Message-ID (diff)
From: Sasha Levin <sasha.levin@oracle.com>
To: Wanpeng Li <liwanp@linux.vnet.ibm.com>,
	Andrew Morton <akpm@linux-foundation.org>
Cc: Michel Lespinasse <walken@google.com>,
	Bob Liu <bob.liu@oracle.com>,
	npiggin@suse.de, kosaki.motohiro@jp.fujitsu.com, riel@redhat.com,
	David Rientjes <rientjes@google.com>,
	Mel Gorman <mgorman@suse.de>, Minchan Kim <minchan@kernel.org>,
	Vlastimil Babka <vbabka@suse.cz>, Hugh Dickins <hughd@google.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm/mlock: fix BUG_ON unlocked page for nolinear VMAs
Date: Tue, 17 Dec 2013 22:32:53 -0500	[thread overview]
Message-ID: <52B11765.8030005@oracle.com> (raw)
In-Reply-To: <20131218032329.GA6044@hacker.(null)>

On 12/17/2013 10:23 PM, Wanpeng Li wrote:
> -			mlock_vma_page(page);   /* no-op if already mlocked */
> -			if (page == check_page)
> +			if (page != check_page && trylock_page(page)) {
> +				mlock_vma_page(page);   /* no-op if already mlocked */
> +				unlock_page(page);
> +			} else if (page == check_page) {
> +				mlock_vma_page(page);  /* no-op if already mlocked */
>   				ret = SWAP_MLOCK;
> +			}

Previously, if page != check_page and the page was locked, we'd call mlock_vma_page()
anyways. With this change, we don't. In fact, we'll just skip that entire block not doing
anything.

If that's something that's never supposed to happen, can we add a

	VM_BUG_ON(page != check_page && PageLocked(page))

Just to cover this new code path?


Thanks,
Sasha

  parent reply	other threads:[~2013-12-18  3:33 UTC|newest]

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-12-17  8:05 [PATCH] mm/mlock: fix BUG_ON unlocked page for nolinear VMAs Wanpeng Li
2013-12-17  8:05 ` Wanpeng Li
2013-12-18  3:14 ` Wanpeng Li
2013-12-18  3:16 ` Wanpeng Li
2013-12-18  3:23   ` Wanpeng Li
     [not found]   ` <20131218032329.GA6044@hacker.(null)>
2013-12-18  3:32     ` Sasha Levin [this message]
2013-12-18  3:32       ` Sasha Levin
2013-12-18  4:12       ` Wanpeng Li
2013-12-18  9:11         ` Vlastimil Babka
2013-12-18  9:11           ` Vlastimil Babka
2013-12-18  9:23           ` Wanpeng Li
     [not found]           ` <52b1699f.87293c0a.75d1.34d3SMTPIN_ADDED_BROKEN@mx.google.com>
2013-12-18 21:43             ` Andrew Morton
2013-12-18 21:43               ` Andrew Morton
2014-01-03 20:17               ` Sasha Levin
2014-01-03 20:17                 ` Sasha Levin
2014-01-03 20:52                 ` Linus Torvalds
2014-01-03 20:52                   ` Linus Torvalds
2014-01-03 23:36                   ` Vlastimil Babka
2014-01-03 23:36                     ` Vlastimil Babka
2014-01-03 23:56                     ` Andrew Morton
2014-01-03 23:56                       ` Andrew Morton
2014-01-04  3:03                       ` Sasha Levin
2014-01-04  3:03                         ` Sasha Levin
2014-01-04  0:18                     ` Linus Torvalds
2014-01-04  0:18                       ` Linus Torvalds
2014-01-04  8:09                       ` Vlastimil Babka
2014-01-04  8:09                         ` Vlastimil Babka
2014-01-05  0:27                       ` Wanpeng Li
2014-01-06 16:47                       ` Motohiro Kosaki
2014-01-06 16:47                         ` Motohiro Kosaki
2014-01-06 22:01                         ` KOSAKI Motohiro
2014-01-06 22:01                           ` KOSAKI Motohiro
2014-01-07  5:27                         ` Wanpeng Li
2014-01-07 15:01                         ` Vlastimil Babka
2014-01-07 15:01                           ` Vlastimil Babka
2014-01-08  1:06                           ` Bob Liu
2014-01-08  1:06                             ` Bob Liu
2014-01-08  2:44                           ` Linus Torvalds
2014-01-08  2:44                             ` Linus Torvalds
2014-01-10 17:48                           ` Motohiro Kosaki
2014-01-10 17:48                             ` Motohiro Kosaki
2014-01-13 14:03                             ` Vlastimil Babka
2014-01-13 14:03                               ` Vlastimil Babka
2014-01-14 11:05                               ` Vlastimil Babka
2014-01-14 11:05                                 ` Vlastimil Babka
2014-01-04  3:31                   ` Bob Liu
2014-01-04  3:31                     ` Bob Liu
2013-12-18  8:54 ` Vlastimil Babka
2013-12-18  8:54   ` Vlastimil Babka
2013-12-18  9:01   ` Wanpeng Li

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