From: Andrea Arcangeli <aarcange@redhat.com>
To: Michel Lespinasse <walken@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Hugh Dickins <hughd@google.com>,
Minchan Kim <minchan.kim@gmail.com>,
Johannes Weiner <jweiner@redhat.com>,
Rik van Riel <riel@redhat.com>, Mel Gorman <mgorman@suse.de>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
Shaohua Li <shaohua.li@intel.com>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: Re: [PATCH] thp: tail page refcounting fix #2
Date: Fri, 26 Aug 2011 21:28:10 +0200 [thread overview]
Message-ID: <20110826192810.GA6439@redhat.com> (raw)
In-Reply-To: <20110826062436.GA5847@google.com>
On Thu, Aug 25, 2011 at 11:24:36PM -0700, Michel Lespinasse wrote:
> In __get_page_tail(), you could add a VM_BUG_ON(page_mapcount(page) <= 0)
> to reflect the fact that get_page() callers are expected to have already
> gotten a reference on the page through a gup call.
Turns out this is going to generate false positives. For THP it should
have been always ok, but if you allocate a compound page (that can't
be splitted) and then map it on 4k pagetables and doing
get_page/put_page in the map/unmap of the pte, it'll fail because the
page fault will be the first occurrence where the tail page refcount
is elevated. I'll check it in more detail tomorrow... So you may want
to delete the bugcheck above before testing #3.
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prev parent reply other threads:[~2011-08-26 19:28 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-19 7:48 [PATCH 0/9] Use RCU to stabilize page counts Michel Lespinasse
2011-08-19 7:48 ` [PATCH 1/9] mm: rcu read lock for getting reference on pages in migration_entry_wait() Michel Lespinasse
2011-08-19 7:48 ` [PATCH 2/9] mm: avoid calling get_page_unless_zero() when charging cgroups Michel Lespinasse
2011-08-19 7:48 ` [PATCH 3/9] mm: rcu read lock when getting from tail to head page Michel Lespinasse
2011-08-19 7:48 ` [PATCH 4/9] mm: use get_page in deactivate_page() Michel Lespinasse
2011-08-19 7:48 ` [PATCH 5/9] kvm: use get_page instead of get_page_unless_zero Michel Lespinasse
2011-08-19 7:48 ` [PATCH 6/9] mm: assert that get_page_unless_zero() callers hold the rcu lock Michel Lespinasse
2011-08-19 23:28 ` Andi Kleen
2011-08-19 7:48 ` [PATCH 7/9] rcu: rcu_get_gp_cookie() / rcu_gp_cookie_elapsed() stand-ins Michel Lespinasse
2011-08-19 7:48 ` [PATCH 8/9] mm: add API for setting a grace period cookie on compound pages Michel Lespinasse
2011-08-19 7:48 ` [PATCH 9/9] mm: make sure tail page counts are stable before splitting THP pages Michel Lespinasse
2011-08-19 7:53 ` [PATCH 0/9] Use RCU to stabilize page counts Michel Lespinasse
2011-08-22 21:33 ` [PATCH] thp: tail page refcounting fix Andrea Arcangeli
2011-08-23 14:55 ` Andrea Arcangeli
2011-08-23 16:45 ` Minchan Kim
2011-08-23 16:54 ` Andrea Arcangeli
2011-08-23 19:52 ` Michel Lespinasse
2011-08-24 0:09 ` Andrea Arcangeli
2011-08-24 0:27 ` Andrea Arcangeli
2011-08-24 13:34 ` [PATCH] thp: tail page refcounting fix #2 Andrea Arcangeli
2011-08-26 6:24 ` Michel Lespinasse
2011-08-26 16:10 ` Andrea Arcangeli
2011-08-26 18:54 ` [PATCH] thp: tail page refcounting fix #3 Andrea Arcangeli
2011-08-27 9:41 ` Michel Lespinasse
2011-08-27 17:34 ` [PATCH] thp: tail page refcounting fix #4 Andrea Arcangeli
2011-08-29 4:20 ` Minchan Kim
2011-09-01 15:24 ` [PATCH] thp: tail page refcounting fix #5 Andrea Arcangeli
2011-09-01 22:27 ` Michel Lespinasse
2011-09-01 23:28 ` Andrew Morton
2011-09-01 23:45 ` Andi Kleen
2011-09-02 0:20 ` Andrea Arcangeli
2011-09-02 1:17 ` Andi Kleen
2011-09-02 0:03 ` Andrew Morton
2011-09-08 16:51 ` [PATCH] thp: tail page refcounting fix #6 Andrea Arcangeli
2011-09-23 15:57 ` Peter Zijlstra
2011-09-30 13:58 ` Andrea Arcangeli
2011-10-16 20:37 ` thp: gup_fast ppc tail refcounting [was Re: [PATCH] thp: tail page refcounting fix #6] Andrea Arcangeli
2011-10-16 20:37 ` [PATCH 1/4] powerpc: remove superfluous PageTail checks on the pte gup_fast Andrea Arcangeli
2011-10-16 20:37 ` [PATCH 2/4] powerpc: get_hugepte() don't put_page() the wrong page Andrea Arcangeli
2011-10-16 20:37 ` [PATCH 3/4] powerpc: gup_hugepte() avoid to free the head page too many times Andrea Arcangeli
2011-10-16 20:37 ` [PATCH 4/4] powerpc: gup_hugepte() support THP based tail recounting Andrea Arcangeli
2011-10-16 20:40 ` thp: gup_fast ppc tail refcounting [was Re: [PATCH] thp: tail page refcounting fix #6] Andrea Arcangeli
2011-10-16 20:40 ` [PATCH 1/4] powerpc: remove superfluous PageTail checks on the pte gup_fast Andrea Arcangeli
2011-10-16 20:40 ` [PATCH 2/4] powerpc: get_hugepte() don't put_page() the wrong page Andrea Arcangeli
2011-10-16 20:40 ` [PATCH 3/4] powerpc: gup_hugepte() avoid to free the head page too many times Andrea Arcangeli
2011-10-16 20:40 ` [PATCH 4/4] powerpc: gup_hugepte() support THP based tail recounting Andrea Arcangeli
2011-10-17 14:41 ` thp: gup_fast s390/sparc tail refcounting [was Re: [PATCH] thp: tail page refcounting fix #6] Andrea Arcangeli
2011-10-17 14:41 ` [PATCH 1/3] s390: gup_huge_pmd() support THP tail recounting Andrea Arcangeli
2011-10-17 14:41 ` [PATCH 2/3] sparc: gup_pte_range() support THP based " Andrea Arcangeli
2011-10-17 22:44 ` David Miller
2011-10-17 14:41 ` [PATCH 3/3] thp: share get_huge_page_tail() Andrea Arcangeli
2011-10-17 21:32 ` fix two more s390/sparc gup_fast bugs Andrea Arcangeli
2011-10-17 21:32 ` [PATCH 1/2] s390: gup_huge_pmd() return 0 if pte changes Andrea Arcangeli
2011-10-17 21:32 ` [PATCH 2/2] powerpc: " Andrea Arcangeli
2011-08-29 22:40 ` [PATCH] thp: tail page refcounting fix #4 Michel Lespinasse
2011-08-29 23:30 ` Andrea Arcangeli
2011-08-26 19:28 ` Andrea Arcangeli [this message]
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