From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
To: Laura Abbott <labbott@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [REGRESSION] !PageLocked(page) assertion with tcpdump
Date: Wed, 10 Aug 2016 19:13:45 +0300 [thread overview]
Message-ID: <20160810161345.GA67522@black.fi.intel.com> (raw)
In-Reply-To: <c711e067-0bff-a6cb-3c37-04dfe77d2db1@redhat.com>
On Wed, Aug 10, 2016 at 07:33:38AM -0700, Laura Abbott wrote:
> Hi,
>
> There have been several reports[1] of assertions tripping when using
> tcpdump on the latest master:
>
> [ 1013.718212] device wlp2s0 entered promiscuous mode
> [ 1013.736003] page:ffffea0004380000 count:2 mapcount:0 mapping:
> (null) index:0x0 compound_mapcount: 0
> [ 1013.736013] flags: 0x17ffffc0004000(head)
> [ 1013.736017] page dumped because: VM_BUG_ON_PAGE(!PageLocked(page))
> [ 1013.736044] ------------[ cut here ]------------
> [ 1013.736091] kernel BUG at mm/rmap.c:1288!
The patch below should do the trick.
WARNING: multiple messages have this Message-ID (diff)
From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
To: Laura Abbott <labbott@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [REGRESSION] !PageLocked(page) assertion with tcpdump
Date: Wed, 10 Aug 2016 19:13:45 +0300 [thread overview]
Message-ID: <20160810161345.GA67522@black.fi.intel.com> (raw)
In-Reply-To: <c711e067-0bff-a6cb-3c37-04dfe77d2db1@redhat.com>
On Wed, Aug 10, 2016 at 07:33:38AM -0700, Laura Abbott wrote:
> Hi,
>
> There have been several reports[1] of assertions tripping when using
> tcpdump on the latest master:
>
> [ 1013.718212] device wlp2s0 entered promiscuous mode
> [ 1013.736003] page:ffffea0004380000 count:2 mapcount:0 mapping:
> (null) index:0x0 compound_mapcount: 0
> [ 1013.736013] flags: 0x17ffffc0004000(head)
> [ 1013.736017] page dumped because: VM_BUG_ON_PAGE(!PageLocked(page))
> [ 1013.736044] ------------[ cut here ]------------
> [ 1013.736091] kernel BUG at mm/rmap.c:1288!
The patch below should do the trick.
>From 8026e3a2cecb7cdd3a63ebc266fb359ef7ec965b Mon Sep 17 00:00:00 2001
From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Date: Wed, 10 Aug 2016 18:51:54 +0300
Subject: [PATCH] mm, rmap: fix false positive VM_BUG() in page_add_file_rmap()
PageTransCompound() doesn't distinguish THP from from any other type of
compound pages. This can lead to false-positive VM_BUG_ON() in
page_add_file_rmap() if called on compound page from a driver[1].
I think we can exclude such cases by checking if the page belong to a
mapping.
The VM_BUG_ON_PAGE() is downgraded to VM_WARN_ON_ONCE(). This path
should not cause any harm to non-THP page, but good to know if we step
on anything else.
[1] http://lkml.kernel.org/r/c711e067-0bff-a6cb-3c37-04dfe77d2db1@redhat.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reported-by: Laura Abbott <labbott@redhat.com>
---
mm/rmap.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/mm/rmap.c b/mm/rmap.c
index eee844997bd8..f071d6f7a986 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1286,8 +1286,9 @@ void page_add_file_rmap(struct page *page, bool compound)
else
__inc_node_page_state(page, NR_FILE_PMDMAPPED);
} else {
- if (PageTransCompound(page)) {
- VM_BUG_ON_PAGE(!PageLocked(page), page);
+ if (PageTransCompound(page) && page_mapping(page)) {
+ VM_WARN_ON_ONCE(!PageLocked(page));
+
SetPageDoubleMap(compound_head(page));
if (PageMlocked(page))
clear_page_mlock(compound_head(page));
--
Kirill A. Shutemov
next prev parent reply other threads:[~2016-08-10 16:13 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-10 14:33 [REGRESSION] !PageLocked(page) assertion with tcpdump Laura Abbott
2016-08-10 14:33 ` Laura Abbott
2016-08-10 16:13 ` Kirill A. Shutemov [this message]
2016-08-10 16:13 ` Kirill A. Shutemov
2016-08-10 20:03 ` Laura Abbott
2016-08-10 20:03 ` Laura Abbott
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