* Re: [PATCH] mm: fix NR_ISOLATED_[ANON|FILE] mismatch
@ 2012-09-19 23:51 Minchan Kim
2012-09-20 12:36 ` KOSAKI Motohiro
2012-09-20 15:41 ` Johannes Weiner
0 siblings, 2 replies; 9+ messages in thread
From: Minchan Kim @ 2012-09-19 23:51 UTC (permalink / raw)
To: Andrew Morton
Cc: KOSAKI Motohiro, linux-mm, linux-kernel, Mel Gorman,
Christoph Lameter, Johannes Weiner, David Rientjes,
Vasiliy Kulikov
On Wed, Sep 19, 2012 at 02:28:10PM -0400, Johannes Weiner wrote:
> On Wed, Sep 19, 2012 at 01:04:56PM -0400, KOSAKI Motohiro wrote:
> > On Wed, Sep 19, 2012 at 3:45 AM, Minchan Kim <minchan@kernel.org> wrote:
> > > When I looked at zone stat mismatch problem, I found
> > > migrate_to_node doesn't decrease NR_ISOLATED_[ANON|FILE]
> > > if check_range fails.
>
> This is a bit misleading. It's not that the stats would be
> inaccurate, it's that the pages would be leaked from the LRU, no?
>
> > > It can make system hang out.
>
> Did you spot this by code review only or did you actually run into
> this? Because...
>
> > > Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> > > Cc: Mel Gorman <mgorman@suse.de>
> > > Cc: Christoph Lameter <cl@linux.com>
> > > Signed-off-by: Minchan Kim <minchan@kernel.org>
> > > ---
> > > mm/mempolicy.c | 16 ++++++++--------
> > > 1 file changed, 8 insertions(+), 8 deletions(-)
> > >
> > > diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> > > index 3d64b36..6bf0860 100644
> > > --- a/mm/mempolicy.c
> > > +++ b/mm/mempolicy.c
> > > @@ -953,16 +953,16 @@ static int migrate_to_node(struct mm_struct *mm, int source, int dest,
> > >
> > > vma = check_range(mm, mm->mmap->vm_start, mm->task_size, &nmask,
> > > flags | MPOL_MF_DISCONTIG_OK, &pagelist);
> > > - if (IS_ERR(vma))
> > > - return PTR_ERR(vma);
> > > -
> > > - if (!list_empty(&pagelist)) {
> > > + if (IS_ERR(vma)) {
> > > + err = PTR_ERR(vma);
> > > + goto out;
> > > + }
> > > + if (!list_empty(&pagelist))
> > > err = migrate_pages(&pagelist, new_node_page, dest,
> > > false, MIGRATE_SYNC);
> > > - if (err)
> > > - putback_lru_pages(&pagelist);
> > > - }
> > > -
> > > +out:
> > > + if (err)
> > > + putback_lru_pages(&pagelist);
> >
> > Good catch!
> > This is a regression since following commit. So, I doubt we need
> > all or nothing semantics. Can we revert it instead? (and probably
> > we need more kind comment for preventing an accident)
>
> I think it makes sense to revert. Not because of the semantics, but I
> just don't see how check_range() could even fail for this callsite:
>
> 1. we pass mm->mmap->vm_start in there, so we should not fail due to
> find_vma()
>
> 2. we pass MPOL_MF_DISCONTIG_OK, so the discontig checks do not apply
> and so can not fail
>
> 3. we pass MPOL_MF_MOVE | MPOL_MF_MOVE_ALL, the page table loops will
> continue until addr == end, so we never fail with -EIO
>
> > commit 0def08e3acc2c9c934e4671487029aed52202d42
> > Author: Vasiliy Kulikov <segooon@gmail.com>
> > Date: Tue Oct 26 14:21:32 2010 -0700
> >
> > mm/mempolicy.c: check return code of check_range
>
> We don't use this code to "check" the range, we use it to collect
> migrate pages. There is no failure case.
>
Here it goes.
>From c2c21b551811e034eb0ede6806e0314b201d7e5b Mon Sep 17 00:00:00 2001
From: Minchan Kim <minchan@kernel.org>
Date: Thu, 20 Sep 2012 08:39:52 +0900
Subject: [PATCH] mm: revert 0def08e3, mm/mempolicy.c: check return code of
check_range
This patch reverts 0def08e3 because check_range can't fail in
migrate_to_node with considering current usecases.
Quote from Johannes
"
I think it makes sense to revert. Not because of the semantics, but I
just don't see how check_range() could even fail for this callsite:
1. we pass mm->mmap->vm_start in there, so we should not fail due to
find_vma()
2. we pass MPOL_MF_DISCONTIG_OK, so the discontig checks do not apply
and so can not fail
3. we pass MPOL_MF_MOVE | MPOL_MF_MOVE_ALL, the page table loops will
continue until addr == end, so we never fail with -EIO
"
And I add new VM_BUG_ON for checking migrate_to_node's future usecase
which might pass to MPOL_MF_STRICT.
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Vasiliy Kulikov <segooon@gmail.com>
Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Minchan Kim <minchan@kernel.org>
---
mm/mempolicy.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 3d64b36..9ec87bd 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -946,15 +946,16 @@ static int migrate_to_node(struct mm_struct *mm, int source, int dest,
nodemask_t nmask;
LIST_HEAD(pagelist);
int err = 0;
- struct vm_area_struct *vma;
nodes_clear(nmask);
node_set(source, nmask);
- vma = check_range(mm, mm->mmap->vm_start, mm->task_size, &nmask,
+ /*
+ * Collect migrate pages and it shoudn't be failed.
+ */
+ VM_BUG_ON(flags & MPOL_MF_STRICT);
+ check_range(mm, mm->mmap->vm_start, mm->task_size, &nmask,
flags | MPOL_MF_DISCONTIG_OK, &pagelist);
- if (IS_ERR(vma))
- return PTR_ERR(vma);
if (!list_empty(&pagelist)) {
err = migrate_pages(&pagelist, new_node_page, dest,
--
1.7.9.5
--
Kind regards,
Minchan Kim
^ permalink raw reply related [flat|nested] 9+ messages in thread
* Re: [PATCH] mm: fix NR_ISOLATED_[ANON|FILE] mismatch
2012-09-19 23:51 [PATCH] mm: fix NR_ISOLATED_[ANON|FILE] mismatch Minchan Kim
@ 2012-09-20 12:36 ` KOSAKI Motohiro
2012-09-20 15:41 ` Johannes Weiner
1 sibling, 0 replies; 9+ messages in thread
From: KOSAKI Motohiro @ 2012-09-20 12:36 UTC (permalink / raw)
To: Minchan Kim
Cc: Andrew Morton, linux-mm, linux-kernel, Mel Gorman,
Christoph Lameter, Johannes Weiner, David Rientjes,
Vasiliy Kulikov
On Wed, Sep 19, 2012 at 7:51 PM, Minchan Kim <minchan@kernel.org> wrote:
> On Wed, Sep 19, 2012 at 02:28:10PM -0400, Johannes Weiner wrote:
>> On Wed, Sep 19, 2012 at 01:04:56PM -0400, KOSAKI Motohiro wrote:
>> > On Wed, Sep 19, 2012 at 3:45 AM, Minchan Kim <minchan@kernel.org> wrote:
>> > > When I looked at zone stat mismatch problem, I found
>> > > migrate_to_node doesn't decrease NR_ISOLATED_[ANON|FILE]
>> > > if check_range fails.
>>
>> This is a bit misleading. It's not that the stats would be
>> inaccurate, it's that the pages would be leaked from the LRU, no?
>>
>> > > It can make system hang out.
>>
>> Did you spot this by code review only or did you actually run into
>> this? Because...
>>
>> > > Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
>> > > Cc: Mel Gorman <mgorman@suse.de>
>> > > Cc: Christoph Lameter <cl@linux.com>
>> > > Signed-off-by: Minchan Kim <minchan@kernel.org>
>> > > ---
>> > > mm/mempolicy.c | 16 ++++++++--------
>> > > 1 file changed, 8 insertions(+), 8 deletions(-)
>> > >
>> > > diff --git a/mm/mempolicy.c b/mm/mempolicy.c
>> > > index 3d64b36..6bf0860 100644
>> > > --- a/mm/mempolicy.c
>> > > +++ b/mm/mempolicy.c
>> > > @@ -953,16 +953,16 @@ static int migrate_to_node(struct mm_struct *mm, int source, int dest,
>> > >
>> > > vma = check_range(mm, mm->mmap->vm_start, mm->task_size, &nmask,
>> > > flags | MPOL_MF_DISCONTIG_OK, &pagelist);
>> > > - if (IS_ERR(vma))
>> > > - return PTR_ERR(vma);
>> > > -
>> > > - if (!list_empty(&pagelist)) {
>> > > + if (IS_ERR(vma)) {
>> > > + err = PTR_ERR(vma);
>> > > + goto out;
>> > > + }
>> > > + if (!list_empty(&pagelist))
>> > > err = migrate_pages(&pagelist, new_node_page, dest,
>> > > false, MIGRATE_SYNC);
>> > > - if (err)
>> > > - putback_lru_pages(&pagelist);
>> > > - }
>> > > -
>> > > +out:
>> > > + if (err)
>> > > + putback_lru_pages(&pagelist);
>> >
>> > Good catch!
>> > This is a regression since following commit. So, I doubt we need
>> > all or nothing semantics. Can we revert it instead? (and probably
>> > we need more kind comment for preventing an accident)
>>
>> I think it makes sense to revert. Not because of the semantics, but I
>> just don't see how check_range() could even fail for this callsite:
>>
>> 1. we pass mm->mmap->vm_start in there, so we should not fail due to
>> find_vma()
>>
>> 2. we pass MPOL_MF_DISCONTIG_OK, so the discontig checks do not apply
>> and so can not fail
>>
>> 3. we pass MPOL_MF_MOVE | MPOL_MF_MOVE_ALL, the page table loops will
>> continue until addr == end, so we never fail with -EIO
>>
>> > commit 0def08e3acc2c9c934e4671487029aed52202d42
>> > Author: Vasiliy Kulikov <segooon@gmail.com>
>> > Date: Tue Oct 26 14:21:32 2010 -0700
>> >
>> > mm/mempolicy.c: check return code of check_range
>>
>> We don't use this code to "check" the range, we use it to collect
>> migrate pages. There is no failure case.
>>
>
> Here it goes.
>
> From c2c21b551811e034eb0ede6806e0314b201d7e5b Mon Sep 17 00:00:00 2001
> From: Minchan Kim <minchan@kernel.org>
> Date: Thu, 20 Sep 2012 08:39:52 +0900
> Subject: [PATCH] mm: revert 0def08e3, mm/mempolicy.c: check return code of
> check_range
>
> This patch reverts 0def08e3 because check_range can't fail in
> migrate_to_node with considering current usecases.
>
> Quote from Johannes
> "
> I think it makes sense to revert. Not because of the semantics, but I
> just don't see how check_range() could even fail for this callsite:
>
> 1. we pass mm->mmap->vm_start in there, so we should not fail due to
> find_vma()
>
> 2. we pass MPOL_MF_DISCONTIG_OK, so the discontig checks do not apply
> and so can not fail
>
> 3. we pass MPOL_MF_MOVE | MPOL_MF_MOVE_ALL, the page table loops will
> continue until addr == end, so we never fail with -EIO
> "
>
> And I add new VM_BUG_ON for checking migrate_to_node's future usecase
> which might pass to MPOL_MF_STRICT.
>
> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> Cc: Mel Gorman <mgorman@suse.de>
> Cc: Christoph Lameter <cl@linux.com>
> Cc: David Rientjes <rientjes@google.com>
> Cc: Vasiliy Kulikov <segooon@gmail.com>
> Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
> Signed-off-by: Minchan Kim <minchan@kernel.org>
> ---
> mm/mempolicy.c | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 3d64b36..9ec87bd 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -946,15 +946,16 @@ static int migrate_to_node(struct mm_struct *mm, int source, int dest,
> nodemask_t nmask;
> LIST_HEAD(pagelist);
> int err = 0;
> - struct vm_area_struct *vma;
>
> nodes_clear(nmask);
> node_set(source, nmask);
>
> - vma = check_range(mm, mm->mmap->vm_start, mm->task_size, &nmask,
> + /*
> + * Collect migrate pages and it shoudn't be failed.
> + */
> + VM_BUG_ON(flags & MPOL_MF_STRICT);
> + check_range(mm, mm->mmap->vm_start, mm->task_size, &nmask,
> flags | MPOL_MF_DISCONTIG_OK, &pagelist);
> - if (IS_ERR(vma))
> - return PTR_ERR(vma);
>
> if (!list_empty(&pagelist)) {
> err = migrate_pages(&pagelist, new_node_page, dest,
Looks good. thank you.
Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH] mm: fix NR_ISOLATED_[ANON|FILE] mismatch
2012-09-19 23:51 [PATCH] mm: fix NR_ISOLATED_[ANON|FILE] mismatch Minchan Kim
2012-09-20 12:36 ` KOSAKI Motohiro
@ 2012-09-20 15:41 ` Johannes Weiner
1 sibling, 0 replies; 9+ messages in thread
From: Johannes Weiner @ 2012-09-20 15:41 UTC (permalink / raw)
To: Minchan Kim
Cc: Andrew Morton, KOSAKI Motohiro, linux-mm, linux-kernel,
Mel Gorman, Christoph Lameter, David Rientjes, Vasiliy Kulikov
On Thu, Sep 20, 2012 at 08:51:56AM +0900, Minchan Kim wrote:
> From: Minchan Kim <minchan@kernel.org>
> Date: Thu, 20 Sep 2012 08:39:52 +0900
> Subject: [PATCH] mm: revert 0def08e3, mm/mempolicy.c: check return code of
> check_range
>
> This patch reverts 0def08e3 because check_range can't fail in
> migrate_to_node with considering current usecases.
>
> Quote from Johannes
> "
> I think it makes sense to revert. Not because of the semantics, but I
> just don't see how check_range() could even fail for this callsite:
>
> 1. we pass mm->mmap->vm_start in there, so we should not fail due to
> find_vma()
>
> 2. we pass MPOL_MF_DISCONTIG_OK, so the discontig checks do not apply
> and so can not fail
>
> 3. we pass MPOL_MF_MOVE | MPOL_MF_MOVE_ALL, the page table loops will
> continue until addr == end, so we never fail with -EIO
> "
>
> And I add new VM_BUG_ON for checking migrate_to_node's future usecase
> which might pass to MPOL_MF_STRICT.
>
> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> Cc: Mel Gorman <mgorman@suse.de>
> Cc: Christoph Lameter <cl@linux.com>
> Cc: David Rientjes <rientjes@google.com>
> Cc: Vasiliy Kulikov <segooon@gmail.com>
> Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
> Signed-off-by: Minchan Kim <minchan@kernel.org>
> ---
> mm/mempolicy.c | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 3d64b36..9ec87bd 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -946,15 +946,16 @@ static int migrate_to_node(struct mm_struct *mm, int source, int dest,
> nodemask_t nmask;
> LIST_HEAD(pagelist);
> int err = 0;
> - struct vm_area_struct *vma;
>
> nodes_clear(nmask);
> node_set(source, nmask);
>
> - vma = check_range(mm, mm->mmap->vm_start, mm->task_size, &nmask,
> + /*
> + * Collect migrate pages and it shoudn't be failed.
> + */
> + VM_BUG_ON(flags & MPOL_MF_STRICT);
Adding a check and a comment is a good idea, but I'm not a big fan of
checking for MPOL_MF_STRICT in particular because it's one of the
invalid inputs, and so you need to extend this check when somebody
extends the spectrum of invalid inputs. I would much prefer checking
directly for !(flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL)) instead, which
would also make the possible inputs apparent without having to chase
up the call chain to find out what is usually passed in.
And how about
/*
* This does not "check" the range but isolates all pages that
* need migration. Between passing in the full user address
* space range and MPOL_MF_DISCONTIG_OK, this call can not fail.
*/
?
> + check_range(mm, mm->mmap->vm_start, mm->task_size, &nmask,
> flags | MPOL_MF_DISCONTIG_OK, &pagelist);
> - if (IS_ERR(vma))
> - return PTR_ERR(vma);
>
> if (!list_empty(&pagelist)) {
> err = migrate_pages(&pagelist, new_node_page, dest,
> --
> 1.7.9.5
>
> --
> Kind regards,
> Minchan Kim
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH] mm: fix NR_ISOLATED_[ANON|FILE] mismatch
2012-09-20 23:24 Minchan Kim
@ 2012-09-21 2:13 ` Johannes Weiner
0 siblings, 0 replies; 9+ messages in thread
From: Johannes Weiner @ 2012-09-21 2:13 UTC (permalink / raw)
To: Minchan Kim
Cc: Andrew Morton, KOSAKI Motohiro, linux-mm, linux-kernel,
Mel Gorman, Christoph Lameter, David Rientjes, Vasiliy Kulikov
On Fri, Sep 21, 2012 at 08:24:08AM +0900, Minchan Kim wrote:
> On Thu, Sep 20, 2012 at 11:41:11AM -0400, Johannes Weiner wrote:
> > On Thu, Sep 20, 2012 at 08:51:56AM +0900, Minchan Kim wrote:
> > > From: Minchan Kim <minchan@kernel.org>
> > > Date: Thu, 20 Sep 2012 08:39:52 +0900
> > > Subject: [PATCH] mm: revert 0def08e3, mm/mempolicy.c: check return code of
> > > check_range
[...]
> From: Minchan Kim <minchan@kernel.org>
> Date: Fri, 21 Sep 2012 08:17:37 +0900
> Subject: [PATCH] mm: enhance comment and bug check
>
> This patch updates comment and bug check.
> It can be fold into [1].
>
> [1] mm-revert-0def08e3-mm-mempolicyc-check-return-code-of-check_range.patch
>
> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
> Signed-off-by: Minchan Kim <minchan@kernel.org>
Thanks! To the patch and this update:
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH] mm: fix NR_ISOLATED_[ANON|FILE] mismatch
@ 2012-09-20 23:24 Minchan Kim
2012-09-21 2:13 ` Johannes Weiner
0 siblings, 1 reply; 9+ messages in thread
From: Minchan Kim @ 2012-09-20 23:24 UTC (permalink / raw)
To: Johannes Weiner, Andrew Morton
Cc: KOSAKI Motohiro, linux-mm, linux-kernel, Mel Gorman,
Christoph Lameter, David Rientjes, Vasiliy Kulikov
On Thu, Sep 20, 2012 at 11:41:11AM -0400, Johannes Weiner wrote:
> On Thu, Sep 20, 2012 at 08:51:56AM +0900, Minchan Kim wrote:
> > From: Minchan Kim <minchan@kernel.org>
> > Date: Thu, 20 Sep 2012 08:39:52 +0900
> > Subject: [PATCH] mm: revert 0def08e3, mm/mempolicy.c: check return code of
> > check_range
> >
> > This patch reverts 0def08e3 because check_range can't fail in
> > migrate_to_node with considering current usecases.
> >
> > Quote from Johannes
> > "
> > I think it makes sense to revert. Not because of the semantics, but I
> > just don't see how check_range() could even fail for this callsite:
> >
> > 1. we pass mm->mmap->vm_start in there, so we should not fail due to
> > find_vma()
> >
> > 2. we pass MPOL_MF_DISCONTIG_OK, so the discontig checks do not apply
> > and so can not fail
> >
> > 3. we pass MPOL_MF_MOVE | MPOL_MF_MOVE_ALL, the page table loops will
> > continue until addr == end, so we never fail with -EIO
> > "
> >
> > And I add new VM_BUG_ON for checking migrate_to_node's future usecase
> > which might pass to MPOL_MF_STRICT.
> >
> > Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> > Cc: Mel Gorman <mgorman@suse.de>
> > Cc: Christoph Lameter <cl@linux.com>
> > Cc: David Rientjes <rientjes@google.com>
> > Cc: Vasiliy Kulikov <segooon@gmail.com>
> > Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
> > Signed-off-by: Minchan Kim <minchan@kernel.org>
> > ---
> > mm/mempolicy.c | 9 +++++----
> > 1 file changed, 5 insertions(+), 4 deletions(-)
> >
> > diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> > index 3d64b36..9ec87bd 100644
> > --- a/mm/mempolicy.c
> > +++ b/mm/mempolicy.c
> > @@ -946,15 +946,16 @@ static int migrate_to_node(struct mm_struct *mm, int source, int dest,
> > nodemask_t nmask;
> > LIST_HEAD(pagelist);
> > int err = 0;
> > - struct vm_area_struct *vma;
> >
> > nodes_clear(nmask);
> > node_set(source, nmask);
> >
> > - vma = check_range(mm, mm->mmap->vm_start, mm->task_size, &nmask,
> > + /*
> > + * Collect migrate pages and it shoudn't be failed.
> > + */
> > + VM_BUG_ON(flags & MPOL_MF_STRICT);
>
> Adding a check and a comment is a good idea, but I'm not a big fan of
> checking for MPOL_MF_STRICT in particular because it's one of the
> invalid inputs, and so you need to extend this check when somebody
> extends the spectrum of invalid inputs. I would much prefer checking
> directly for !(flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL)) instead, which
> would also make the possible inputs apparent without having to chase
> up the call chain to find out what is usually passed in.
>
> And how about
>
> /*
> * This does not "check" the range but isolates all pages that
> * need migration. Between passing in the full user address
> * space range and MPOL_MF_DISCONTIG_OK, this call can not fail.
> */
>
> ?
Good idea. Thanks Hannes,
>From 13ae84083ac1f057eafbeae49efba862aa7a470e Mon Sep 17 00:00:00 2001
From: Minchan Kim <minchan@kernel.org>
Date: Fri, 21 Sep 2012 08:17:37 +0900
Subject: [PATCH] mm: enhance comment and bug check
This patch updates comment and bug check.
It can be fold into [1].
[1] mm-revert-0def08e3-mm-mempolicyc-check-return-code-of-check_range.patch
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Minchan Kim <minchan@kernel.org>
---
mm/mempolicy.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 9ec87bd..0b78fb9 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -951,9 +951,11 @@ static int migrate_to_node(struct mm_struct *mm, int source, int dest,
node_set(source, nmask);
/*
- * Collect migrate pages and it shoudn't be failed.
+ * This does not "check" the range but isolates all pages that
+ * need migration. Between passing in the full user address
+ * space range and MPOL_MF_DISCONTIG_OK, this call can not fail.
*/
- VM_BUG_ON(flags & MPOL_MF_STRICT);
+ VM_BUG_ON(!(flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL)));
check_range(mm, mm->mmap->vm_start, mm->task_size, &nmask,
flags | MPOL_MF_DISCONTIG_OK, &pagelist);
--
1.7.9.5
--
Kind regards,
Minchan Kim
^ permalink raw reply related [flat|nested] 9+ messages in thread
* Re: [PATCH] mm: fix NR_ISOLATED_[ANON|FILE] mismatch
2012-09-19 18:28 ` Johannes Weiner
@ 2012-09-19 20:38 ` Minchan Kim
0 siblings, 0 replies; 9+ messages in thread
From: Minchan Kim @ 2012-09-19 20:38 UTC (permalink / raw)
To: Johannes Weiner
Cc: KOSAKI Motohiro, Andrew Morton, linux-mm, linux-kernel,
Mel Gorman, Christoph Lameter
Hi Hannes,
On Wed, Sep 19, 2012 at 02:28:10PM -0400, Johannes Weiner wrote:
> On Wed, Sep 19, 2012 at 01:04:56PM -0400, KOSAKI Motohiro wrote:
> > On Wed, Sep 19, 2012 at 3:45 AM, Minchan Kim <minchan@kernel.org> wrote:
> > > When I looked at zone stat mismatch problem, I found
> > > migrate_to_node doesn't decrease NR_ISOLATED_[ANON|FILE]
> > > if check_range fails.
>
> This is a bit misleading. It's not that the stats would be
> inaccurate, it's that the pages would be leaked from the LRU, no?
>
> > > It can make system hang out.
>
> Did you spot this by code review only or did you actually run into
> this? Because...
Just by code review during the bug of memory-hotplug.
>
> > > Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> > > Cc: Mel Gorman <mgorman@suse.de>
> > > Cc: Christoph Lameter <cl@linux.com>
> > > Signed-off-by: Minchan Kim <minchan@kernel.org>
> > > ---
> > > mm/mempolicy.c | 16 ++++++++--------
> > > 1 file changed, 8 insertions(+), 8 deletions(-)
> > >
> > > diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> > > index 3d64b36..6bf0860 100644
> > > --- a/mm/mempolicy.c
> > > +++ b/mm/mempolicy.c
> > > @@ -953,16 +953,16 @@ static int migrate_to_node(struct mm_struct *mm, int source, int dest,
> > >
> > > vma = check_range(mm, mm->mmap->vm_start, mm->task_size, &nmask,
> > > flags | MPOL_MF_DISCONTIG_OK, &pagelist);
> > > - if (IS_ERR(vma))
> > > - return PTR_ERR(vma);
> > > -
> > > - if (!list_empty(&pagelist)) {
> > > + if (IS_ERR(vma)) {
> > > + err = PTR_ERR(vma);
> > > + goto out;
> > > + }
> > > + if (!list_empty(&pagelist))
> > > err = migrate_pages(&pagelist, new_node_page, dest,
> > > false, MIGRATE_SYNC);
> > > - if (err)
> > > - putback_lru_pages(&pagelist);
> > > - }
> > > -
> > > +out:
> > > + if (err)
> > > + putback_lru_pages(&pagelist);
> >
> > Good catch!
> > This is a regression since following commit. So, I doubt we need
> > all or nothing semantics. Can we revert it instead? (and probably
> > we need more kind comment for preventing an accident)
>
> I think it makes sense to revert. Not because of the semantics, but I
> just don't see how check_range() could even fail for this callsite:
>
> 1. we pass mm->mmap->vm_start in there, so we should not fail due to
> find_vma()
>
> 2. we pass MPOL_MF_DISCONTIG_OK, so the discontig checks do not apply
> and so can not fail
>
> 3. we pass MPOL_MF_MOVE | MPOL_MF_MOVE_ALL, the page table loops will
> continue until addr == end, so we never fail with -EIO
>
> > commit 0def08e3acc2c9c934e4671487029aed52202d42
> > Author: Vasiliy Kulikov <segooon@gmail.com>
> > Date: Tue Oct 26 14:21:32 2010 -0700
> >
> > mm/mempolicy.c: check return code of check_range
>
> We don't use this code to "check" the range, we use it to collect
> migrate pages. There is no failure case.
Right. I will send revert patch when I go to office.
Thanks for the pointing out.
--
Kind Regards,
Minchan Kim
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH] mm: fix NR_ISOLATED_[ANON|FILE] mismatch
2012-09-19 17:04 ` KOSAKI Motohiro
@ 2012-09-19 18:28 ` Johannes Weiner
2012-09-19 20:38 ` Minchan Kim
0 siblings, 1 reply; 9+ messages in thread
From: Johannes Weiner @ 2012-09-19 18:28 UTC (permalink / raw)
To: KOSAKI Motohiro
Cc: Minchan Kim, Andrew Morton, linux-mm, linux-kernel, Mel Gorman,
Christoph Lameter
On Wed, Sep 19, 2012 at 01:04:56PM -0400, KOSAKI Motohiro wrote:
> On Wed, Sep 19, 2012 at 3:45 AM, Minchan Kim <minchan@kernel.org> wrote:
> > When I looked at zone stat mismatch problem, I found
> > migrate_to_node doesn't decrease NR_ISOLATED_[ANON|FILE]
> > if check_range fails.
This is a bit misleading. It's not that the stats would be
inaccurate, it's that the pages would be leaked from the LRU, no?
> > It can make system hang out.
Did you spot this by code review only or did you actually run into
this? Because...
> > Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> > Cc: Mel Gorman <mgorman@suse.de>
> > Cc: Christoph Lameter <cl@linux.com>
> > Signed-off-by: Minchan Kim <minchan@kernel.org>
> > ---
> > mm/mempolicy.c | 16 ++++++++--------
> > 1 file changed, 8 insertions(+), 8 deletions(-)
> >
> > diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> > index 3d64b36..6bf0860 100644
> > --- a/mm/mempolicy.c
> > +++ b/mm/mempolicy.c
> > @@ -953,16 +953,16 @@ static int migrate_to_node(struct mm_struct *mm, int source, int dest,
> >
> > vma = check_range(mm, mm->mmap->vm_start, mm->task_size, &nmask,
> > flags | MPOL_MF_DISCONTIG_OK, &pagelist);
> > - if (IS_ERR(vma))
> > - return PTR_ERR(vma);
> > -
> > - if (!list_empty(&pagelist)) {
> > + if (IS_ERR(vma)) {
> > + err = PTR_ERR(vma);
> > + goto out;
> > + }
> > + if (!list_empty(&pagelist))
> > err = migrate_pages(&pagelist, new_node_page, dest,
> > false, MIGRATE_SYNC);
> > - if (err)
> > - putback_lru_pages(&pagelist);
> > - }
> > -
> > +out:
> > + if (err)
> > + putback_lru_pages(&pagelist);
>
> Good catch!
> This is a regression since following commit. So, I doubt we need
> all or nothing semantics. Can we revert it instead? (and probably
> we need more kind comment for preventing an accident)
I think it makes sense to revert. Not because of the semantics, but I
just don't see how check_range() could even fail for this callsite:
1. we pass mm->mmap->vm_start in there, so we should not fail due to
find_vma()
2. we pass MPOL_MF_DISCONTIG_OK, so the discontig checks do not apply
and so can not fail
3. we pass MPOL_MF_MOVE | MPOL_MF_MOVE_ALL, the page table loops will
continue until addr == end, so we never fail with -EIO
> commit 0def08e3acc2c9c934e4671487029aed52202d42
> Author: Vasiliy Kulikov <segooon@gmail.com>
> Date: Tue Oct 26 14:21:32 2010 -0700
>
> mm/mempolicy.c: check return code of check_range
We don't use this code to "check" the range, we use it to collect
migrate pages. There is no failure case.
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH] mm: fix NR_ISOLATED_[ANON|FILE] mismatch
2012-09-19 7:45 Minchan Kim
@ 2012-09-19 17:04 ` KOSAKI Motohiro
2012-09-19 18:28 ` Johannes Weiner
0 siblings, 1 reply; 9+ messages in thread
From: KOSAKI Motohiro @ 2012-09-19 17:04 UTC (permalink / raw)
To: Minchan Kim
Cc: Andrew Morton, linux-mm, linux-kernel, Mel Gorman, Christoph Lameter
On Wed, Sep 19, 2012 at 3:45 AM, Minchan Kim <minchan@kernel.org> wrote:
> When I looked at zone stat mismatch problem, I found
> migrate_to_node doesn't decrease NR_ISOLATED_[ANON|FILE]
> if check_range fails.
>
> It can make system hang out.
>
> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> Cc: Mel Gorman <mgorman@suse.de>
> Cc: Christoph Lameter <cl@linux.com>
> Signed-off-by: Minchan Kim <minchan@kernel.org>
> ---
> mm/mempolicy.c | 16 ++++++++--------
> 1 file changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 3d64b36..6bf0860 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -953,16 +953,16 @@ static int migrate_to_node(struct mm_struct *mm, int source, int dest,
>
> vma = check_range(mm, mm->mmap->vm_start, mm->task_size, &nmask,
> flags | MPOL_MF_DISCONTIG_OK, &pagelist);
> - if (IS_ERR(vma))
> - return PTR_ERR(vma);
> -
> - if (!list_empty(&pagelist)) {
> + if (IS_ERR(vma)) {
> + err = PTR_ERR(vma);
> + goto out;
> + }
> + if (!list_empty(&pagelist))
> err = migrate_pages(&pagelist, new_node_page, dest,
> false, MIGRATE_SYNC);
> - if (err)
> - putback_lru_pages(&pagelist);
> - }
> -
> +out:
> + if (err)
> + putback_lru_pages(&pagelist);
Good catch!
This is a regression since following commit. So, I doubt we need
all or nothing semantics. Can we revert it instead? (and probably
we need more kind comment for preventing an accident)
commit 0def08e3acc2c9c934e4671487029aed52202d42
Author: Vasiliy Kulikov <segooon@gmail.com>
Date: Tue Oct 26 14:21:32 2010 -0700
mm/mempolicy.c: check return code of check_range
^ permalink raw reply [flat|nested] 9+ messages in thread
* [PATCH] mm: fix NR_ISOLATED_[ANON|FILE] mismatch
@ 2012-09-19 7:45 Minchan Kim
2012-09-19 17:04 ` KOSAKI Motohiro
0 siblings, 1 reply; 9+ messages in thread
From: Minchan Kim @ 2012-09-19 7:45 UTC (permalink / raw)
To: Andrew Morton
Cc: linux-mm, linux-kernel, Minchan Kim, KOSAKI Motohiro, Mel Gorman,
Christoph Lameter
When I looked at zone stat mismatch problem, I found
migrate_to_node doesn't decrease NR_ISOLATED_[ANON|FILE]
if check_range fails.
It can make system hang out.
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Christoph Lameter <cl@linux.com>
Signed-off-by: Minchan Kim <minchan@kernel.org>
---
mm/mempolicy.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 3d64b36..6bf0860 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -953,16 +953,16 @@ static int migrate_to_node(struct mm_struct *mm, int source, int dest,
vma = check_range(mm, mm->mmap->vm_start, mm->task_size, &nmask,
flags | MPOL_MF_DISCONTIG_OK, &pagelist);
- if (IS_ERR(vma))
- return PTR_ERR(vma);
-
- if (!list_empty(&pagelist)) {
+ if (IS_ERR(vma)) {
+ err = PTR_ERR(vma);
+ goto out;
+ }
+ if (!list_empty(&pagelist))
err = migrate_pages(&pagelist, new_node_page, dest,
false, MIGRATE_SYNC);
- if (err)
- putback_lru_pages(&pagelist);
- }
-
+out:
+ if (err)
+ putback_lru_pages(&pagelist);
return err;
}
--
1.7.9.5
^ permalink raw reply related [flat|nested] 9+ messages in thread
end of thread, other threads:[~2012-09-21 2:14 UTC | newest]
Thread overview: 9+ messages (download: mbox.gz / follow: Atom feed)
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2012-09-19 23:51 [PATCH] mm: fix NR_ISOLATED_[ANON|FILE] mismatch Minchan Kim
2012-09-20 12:36 ` KOSAKI Motohiro
2012-09-20 15:41 ` Johannes Weiner
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2012-09-20 23:24 Minchan Kim
2012-09-21 2:13 ` Johannes Weiner
2012-09-19 7:45 Minchan Kim
2012-09-19 17:04 ` KOSAKI Motohiro
2012-09-19 18:28 ` Johannes Weiner
2012-09-19 20:38 ` Minchan Kim
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