* [PATCH v2] mm: vmscan: add VM_BUG_ON on illegal return values from scan_objects
@ 2013-05-21 7:13 Oskar Andero
2013-05-21 7:17 ` Pekka Enberg
0 siblings, 1 reply; 3+ messages in thread
From: Oskar Andero @ 2013-05-21 7:13 UTC (permalink / raw)
To: linux-kernel, linux-mm
Cc: Radovan Lekanovic, David Rientjes, Oskar Andero, Glauber Costa,
Dave Chinner, Andrew Morton, Hugh Dickins, Greg Kroah-Hartman
Add a VM_BUG_ON to catch any illegal value from the shrinkers. It's a
potential bug if scan_objects returns a negative other than -1 and
would lead to undefined behaviour.
Cc: Glauber Costa <glommer@openvz.org>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Oskar Andero <oskar.andero@sonymobile.com>
---
mm/vmscan.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 6bac41e..63fec86 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -293,6 +293,7 @@ shrink_slab_one(struct shrinker *shrinker, struct shrink_control *shrinkctl,
ret = shrinker->scan_objects(shrinker, shrinkctl);
if (ret == -1)
break;
+ VM_BUG_ON(ret < -1);
freed += ret;
count_vm_events(SLABS_SCANNED, nr_to_scan);
--
1.8.1.5
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v2] mm: vmscan: add VM_BUG_ON on illegal return values from scan_objects
2013-05-21 7:13 [PATCH v2] mm: vmscan: add VM_BUG_ON on illegal return values from scan_objects Oskar Andero
@ 2013-05-21 7:17 ` Pekka Enberg
2013-05-21 7:28 ` Glauber Costa
0 siblings, 1 reply; 3+ messages in thread
From: Pekka Enberg @ 2013-05-21 7:17 UTC (permalink / raw)
To: Oskar Andero
Cc: LKML, linux-mm, Radovan Lekanovic, David Rientjes, Glauber Costa,
Dave Chinner, Andrew Morton, Hugh Dickins, Greg Kroah-Hartman
On Tue, May 21, 2013 at 10:13 AM, Oskar Andero
<oskar.andero@sonymobile.com> wrote:
> Add a VM_BUG_ON to catch any illegal value from the shrinkers. It's a
> potential bug if scan_objects returns a negative other than -1 and
> would lead to undefined behaviour.
>
> Cc: Glauber Costa <glommer@openvz.org>
> Cc: Dave Chinner <dchinner@redhat.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Hugh Dickins <hughd@google.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Signed-off-by: Oskar Andero <oskar.andero@sonymobile.com>
> ---
> mm/vmscan.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 6bac41e..63fec86 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -293,6 +293,7 @@ shrink_slab_one(struct shrinker *shrinker, struct shrink_control *shrinkctl,
> ret = shrinker->scan_objects(shrinker, shrinkctl);
> if (ret == -1)
> break;
> + VM_BUG_ON(ret < -1);
It seems to me relaxing the shrinker API restrictions and changing the
"ret == -1" to "ret < 0" would be a much more robust approach...
> freed += ret;
>
> count_vm_events(SLABS_SCANNED, nr_to_scan);
> --
> 1.8.1.5
>
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v2] mm: vmscan: add VM_BUG_ON on illegal return values from scan_objects
2013-05-21 7:17 ` Pekka Enberg
@ 2013-05-21 7:28 ` Glauber Costa
0 siblings, 0 replies; 3+ messages in thread
From: Glauber Costa @ 2013-05-21 7:28 UTC (permalink / raw)
To: Pekka Enberg
Cc: Oskar Andero, LKML, linux-mm, Radovan Lekanovic, David Rientjes,
Glauber Costa, Dave Chinner, Andrew Morton, Hugh Dickins,
Greg Kroah-Hartman
On 05/21/2013 11:17 AM, Pekka Enberg wrote:
> It seems to me relaxing the shrinker API restrictions and changing the
> "ret == -1" to "ret < 0" would be a much more robust approach...
Dave had already spoken against it, and I agree with him
Anybody returning any negative value different than -1 is definitely
doing something strange
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^ permalink raw reply [flat|nested] 3+ messages in thread
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2013-05-21 7:13 [PATCH v2] mm: vmscan: add VM_BUG_ON on illegal return values from scan_objects Oskar Andero
2013-05-21 7:17 ` Pekka Enberg
2013-05-21 7:28 ` Glauber Costa
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