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 <glommer@xxxxxxxxxx> > Cc: Dave Chinner <dchinner@xxxxxxxxxx> > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > Cc: Hugh Dickins <hughd@xxxxxxxxxx> > Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > Signed-off-by: Oskar Andero <oskar.andero@xxxxxxxxxxxxxx> > --- > 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 dchinner@xxxxxxxxxx -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>