From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Dmitry Vyukov <dvyukov@google.com>,
Doug Gilbert <dgilbert@interlog.com>,
David Rientjes <rientjes@google.com>,
Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Shiraz Hashim <shashim@codeaurora.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
Hugh Dickins <hughd@google.com>,
Sasha Levin <sasha.levin@oracle.com>,
syzkaller <syzkaller@googlegroups.com>,
Kostya Serebryany <kcc@google.com>,
Alexander Potapenko <glider@google.com>,
linux-scsi@vger.kernel.org
Subject: Re: mm: VM_BUG_ON_PAGE(PageTail(page)) in mbind
Date: Tue, 26 Jan 2016 23:07:43 +0200 [thread overview]
Message-ID: <20160126210743.GB22852@node.shutemov.name> (raw)
In-Reply-To: <20160126124823.15b08f0a53dd9671fbc685d9@linux-foundation.org>
On Tue, Jan 26, 2016 at 12:48:23PM -0800, Andrew Morton wrote:
> On Tue, 26 Jan 2016 22:28:29 +0200 "Kirill A. Shutemov" <kirill@shutemov.name> wrote:
>
> > The patch below fixes the issue for me, but this bug makes me wounder how
> > many bugs like this we have in kernel... :-/
> >
> > Looks like we are too permissive about which VMA is migratable:
> > vma_migratable() filters out VMA by VM_IO and VM_PFNMAP.
> > I think VM_DONTEXPAND also correlate with VMA which cannot be migrated.
> >
> > $ git grep VM_DONTEXPAND drivers | grep -v '\(VM_IO\|VM_PFNMAN\)' | wc -l
> > 33
> >
> > Hm.. :-|
> >
> > It worth looking on them closely... And I wouldn't be surprised if some
> > VMAs without all of these flags are not migratable too.
> >
> > Sigh.. Any thoughts?
>
> Sigh indeed. I think that both VM_DONTEXPAND and VM_DONTDUMP are
> pretty good signs that mbind() should not be mucking with this vma. If
> such a policy sometimes results in mbind failing to set a policy then
> that's not a huge loss - something runs a bit slower maybe.
>
> I mean, we only really expect mbind() to operate against regular old
> anon/pagecache memory, yes?
Well, it can work fine too if driver itself uses page tables to find out
which pages it should to operate on. I don't think it's a common case.
--
Kirill A. Shutemov
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WARNING: multiple messages have this Message-ID (diff)
From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Dmitry Vyukov <dvyukov@google.com>,
Doug Gilbert <dgilbert@interlog.com>,
David Rientjes <rientjes@google.com>,
Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Shiraz Hashim <shashim@codeaurora.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
Hugh Dickins <hughd@google.com>,
Sasha Levin <sasha.levin@oracle.com>,
syzkaller <syzkaller@googlegroups.com>,
Kostya Serebryany <kcc@google.com>,
Alexander Potapenko <glider@google.com>,
linux-scsi@vger.kernel.org
Subject: Re: mm: VM_BUG_ON_PAGE(PageTail(page)) in mbind
Date: Tue, 26 Jan 2016 23:07:43 +0200 [thread overview]
Message-ID: <20160126210743.GB22852@node.shutemov.name> (raw)
In-Reply-To: <20160126124823.15b08f0a53dd9671fbc685d9@linux-foundation.org>
On Tue, Jan 26, 2016 at 12:48:23PM -0800, Andrew Morton wrote:
> On Tue, 26 Jan 2016 22:28:29 +0200 "Kirill A. Shutemov" <kirill@shutemov.name> wrote:
>
> > The patch below fixes the issue for me, but this bug makes me wounder how
> > many bugs like this we have in kernel... :-/
> >
> > Looks like we are too permissive about which VMA is migratable:
> > vma_migratable() filters out VMA by VM_IO and VM_PFNMAP.
> > I think VM_DONTEXPAND also correlate with VMA which cannot be migrated.
> >
> > $ git grep VM_DONTEXPAND drivers | grep -v '\(VM_IO\|VM_PFNMAN\)' | wc -l
> > 33
> >
> > Hm.. :-|
> >
> > It worth looking on them closely... And I wouldn't be surprised if some
> > VMAs without all of these flags are not migratable too.
> >
> > Sigh.. Any thoughts?
>
> Sigh indeed. I think that both VM_DONTEXPAND and VM_DONTDUMP are
> pretty good signs that mbind() should not be mucking with this vma. If
> such a policy sometimes results in mbind failing to set a policy then
> that's not a huge loss - something runs a bit slower maybe.
>
> I mean, we only really expect mbind() to operate against regular old
> anon/pagecache memory, yes?
Well, it can work fine too if driver itself uses page tables to find out
which pages it should to operate on. I don't think it's a common case.
--
Kirill A. Shutemov
next prev parent reply other threads:[~2016-01-26 21:07 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-26 12:52 mm: VM_BUG_ON_PAGE(PageTail(page)) in mbind Dmitry Vyukov
2016-01-26 12:52 ` Dmitry Vyukov
2016-01-26 20:28 ` Kirill A. Shutemov
2016-01-26 20:28 ` Kirill A. Shutemov
2016-01-26 20:28 ` Kirill A. Shutemov
2016-01-26 20:48 ` Andrew Morton
2016-01-26 20:48 ` Andrew Morton
2016-01-26 21:07 ` Kirill A. Shutemov [this message]
2016-01-26 21:07 ` Kirill A. Shutemov
2016-01-26 20:49 ` Andrew Morton
2016-01-26 20:49 ` Andrew Morton
2016-01-26 21:05 ` Kirill A. Shutemov
2016-01-26 21:05 ` Kirill A. Shutemov
2016-01-26 21:37 ` Vlastimil Babka
2016-01-26 21:37 ` Vlastimil Babka
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