Re: [PATCH 2/3] mm: unify checks in alloc_pages_node() and __alloc_pages_node()

[Michal Hocko <mhocko@kernel.org>]

On Thu 20-08-15 16:14:34, Michal Hocko wrote:
> On Thu 20-08-15 13:43:21, Vlastimil Babka wrote:
> > Perform the same debug checks in alloc_pages_node() as are done in
> > __alloc_pages_node(), by making the former function a wrapper of the latter
> > one.
> > 
> > In addition to better diagnostics in DEBUG_VM builds for situations which
> > have been already fatal (e.g. out-of-bounds node id), there are two visible
> > changes for potential existing buggy callers of alloc_pages_node():
> > 
> > - calling alloc_pages_node() with any negative nid (e.g. due to arithmetic
> >   overflow) was treated as passing NUMA_NO_NODE and fallback to local node was
> >   applied. This will now be fatal.
> 
> OK, this is sensible
> 
> > - calling alloc_pages_node() with an offline node will now be checked for
> >   DEBUG_VM builds. Since it's not fatal if the node has been previously online,
> >   and this patch may expose some existing buggy callers, change the VM_BUG_ON
> >   in __alloc_pages_node() to VM_WARN_ON.
> 
> Yes, bugging on just because we race with memory hotplug or use
> stale node number is not appropriate because the fallback is
> straightforward. A warning should help to identify and fix those place.
> 
> > 
> > Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
> > Acked-by: David Rientjes <rientjes@google.com>
> > Acked-by: Johannes Weiner <hannes@cmpxchg.org>
> > Acked-by: Christoph Lameter <cl@linux.com>

Forgot to add
Acked-by: Michal Hocko <mhocko@suse.com>
-- 
Michal Hocko
SUSE Labs