Re: [PATCH] mm: vmscan: add BUG_ON on illegal return values from scan_objects
On Mon, May 20, 2013 at 11:14:27AM +0200, Oskar Andero wrote: > Add a BUG_ON to catch any illegal value from the shrinkers. This fixes a > potential bug if scan_objects returns a negative other than -1, which > would lead to undefined behaviour. > > Cc: Glauber Costa > Cc: Dave Chinner > Cc: Andrew Morton > Cc: Hugh Dickins > Cc: Greg Kroah-Hartman > Signed-off-by: Oskar Andero > --- > mm/vmscan.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 6bac41e..fbe6742 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; > + BUG_ON(ret < -1); > freed += ret; > > count_vm_events(SLABS_SCANNED, nr_to_scan); NACK. we've got to fix the damn shrinkers first. If you want this sort of guard added to the patchset Glauber and I are working on that does this, then discuss it in the context of that patch set. Even if you do, you'll get the same answer: we need to first all the busted shrinkers before we even consider being nasty about enforcing the API constraints to prevent furture breakage. If you want to do something useful, look at all the comments about broken shrinkers in Glauber's patch set and work with the owners of the code to understand what they really need and get them fixed. -Dave. -- Dave Chinner dchin...@redhat.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] mm: vmscan: add BUG_ON on illegal return values from scan_objects
On Mon, May 20, 2013 at 11:14:27AM +0200, Oskar Andero wrote: Add a BUG_ON to catch any illegal value from the shrinkers. This fixes a potential bug if scan_objects returns a negative other than -1, which would lead to undefined behaviour. Cc: Glauber Costa glom...@openvz.org Cc: Dave Chinner dchin...@redhat.com Cc: Andrew Morton a...@linux-foundation.org Cc: Hugh Dickins hu...@google.com Cc: Greg Kroah-Hartman gre...@linuxfoundation.org Signed-off-by: Oskar Andero oskar.and...@sonymobile.com --- mm/vmscan.c | 1 + 1 file changed, 1 insertion(+) diff --git a/mm/vmscan.c b/mm/vmscan.c index 6bac41e..fbe6742 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; + BUG_ON(ret -1); freed += ret; count_vm_events(SLABS_SCANNED, nr_to_scan); NACK. we've got to fix the damn shrinkers first. If you want this sort of guard added to the patchset Glauber and I are working on that does this, then discuss it in the context of that patch set. Even if you do, you'll get the same answer: we need to first all the busted shrinkers before we even consider being nasty about enforcing the API constraints to prevent furture breakage. If you want to do something useful, look at all the comments about broken shrinkers in Glauber's patch set and work with the owners of the code to understand what they really need and get them fixed. -Dave. -- Dave Chinner dchin...@redhat.com -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] mm: vmscan: add BUG_ON on illegal return values from scan_objects
On Mon, 20 May 2013, Oskar Andero wrote: > Add a BUG_ON to catch any illegal value from the shrinkers. This fixes a > potential bug if scan_objects returns a negative other than -1, which > would lead to undefined behaviour. > > Cc: Glauber Costa > Cc: Dave Chinner > Cc: Andrew Morton > Cc: Hugh Dickins > Cc: Greg Kroah-Hartman > Signed-off-by: Oskar Andero > --- > mm/vmscan.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 6bac41e..fbe6742 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; > + BUG_ON(ret < -1); > freed += ret; > > count_vm_events(SLABS_SCANNED, nr_to_scan); Nack, this doesn't fix anything. I can see the intention, and for that it might make sense to turn this into VM_BUG_ON() so that anybody debugging an issue related to this with CONFIG_DEBUG_VM would get the indication, but I don't think we need to enforce the API with BUG_ON(). -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] mm: vmscan: add BUG_ON on illegal return values from scan_objects
On Mon, May 20, 2013 at 11:14:27AM +0200, Oskar Andero wrote: > Add a BUG_ON to catch any illegal value from the shrinkers. This fixes a > potential bug if scan_objects returns a negative other than -1, which > would lead to undefined behaviour. So it's better to crash a machine and keep anyone from using it? Instead of recovering from an error you found? Not good. greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH] mm: vmscan: add BUG_ON on illegal return values from scan_objects
Add a BUG_ON to catch any illegal value from the shrinkers. This fixes a potential bug if scan_objects returns a negative other than -1, which would lead to undefined behaviour. Cc: Glauber Costa Cc: Dave Chinner Cc: Andrew Morton Cc: Hugh Dickins Cc: Greg Kroah-Hartman Signed-off-by: Oskar Andero --- mm/vmscan.c | 1 + 1 file changed, 1 insertion(+) diff --git a/mm/vmscan.c b/mm/vmscan.c index 6bac41e..fbe6742 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; + BUG_ON(ret < -1); freed += ret; count_vm_events(SLABS_SCANNED, nr_to_scan); -- 1.8.1.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH] mm: vmscan: add BUG_ON on illegal return values from scan_objects
Add a BUG_ON to catch any illegal value from the shrinkers. This fixes a potential bug if scan_objects returns a negative other than -1, which would lead to undefined behaviour. Cc: Glauber Costa glom...@openvz.org Cc: Dave Chinner dchin...@redhat.com Cc: Andrew Morton a...@linux-foundation.org Cc: Hugh Dickins hu...@google.com Cc: Greg Kroah-Hartman gre...@linuxfoundation.org Signed-off-by: Oskar Andero oskar.and...@sonymobile.com --- mm/vmscan.c | 1 + 1 file changed, 1 insertion(+) diff --git a/mm/vmscan.c b/mm/vmscan.c index 6bac41e..fbe6742 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; + BUG_ON(ret -1); freed += ret; count_vm_events(SLABS_SCANNED, nr_to_scan); -- 1.8.1.5 -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] mm: vmscan: add BUG_ON on illegal return values from scan_objects
On Mon, May 20, 2013 at 11:14:27AM +0200, Oskar Andero wrote: Add a BUG_ON to catch any illegal value from the shrinkers. This fixes a potential bug if scan_objects returns a negative other than -1, which would lead to undefined behaviour. So it's better to crash a machine and keep anyone from using it? Instead of recovering from an error you found? Not good. greg k-h -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] mm: vmscan: add BUG_ON on illegal return values from scan_objects
On Mon, 20 May 2013, Oskar Andero wrote: Add a BUG_ON to catch any illegal value from the shrinkers. This fixes a potential bug if scan_objects returns a negative other than -1, which would lead to undefined behaviour. Cc: Glauber Costa glom...@openvz.org Cc: Dave Chinner dchin...@redhat.com Cc: Andrew Morton a...@linux-foundation.org Cc: Hugh Dickins hu...@google.com Cc: Greg Kroah-Hartman gre...@linuxfoundation.org Signed-off-by: Oskar Andero oskar.and...@sonymobile.com --- mm/vmscan.c | 1 + 1 file changed, 1 insertion(+) diff --git a/mm/vmscan.c b/mm/vmscan.c index 6bac41e..fbe6742 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; + BUG_ON(ret -1); freed += ret; count_vm_events(SLABS_SCANNED, nr_to_scan); Nack, this doesn't fix anything. I can see the intention, and for that it might make sense to turn this into VM_BUG_ON() so that anybody debugging an issue related to this with CONFIG_DEBUG_VM would get the indication, but I don't think we need to enforce the API with BUG_ON(). -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
