| Message ID | 20211206033338.743270-2-npache@redhat.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm: Dont allocate pages on a offline node | expand |
On Sun, Dec 05, 2021 at 10:33:37PM -0500, Nico Pache wrote: > We shouldn't allocate pages on a unavailable node. Add a check for this > in __alloc_pages_node and return NULL to avoid issues further down the > callchain. > > Also update the VM_WARN_ON in __alloc_pages_node which could skip this > warn if the gfp_mask is not GFP_THISNODE. Why is this not also needed in __folio_alloc_node()?
On Sun 05-12-21 22:33:37, Nico Pache wrote: > We shouldn't allocate pages on a unavailable node. Add a check for this > in __alloc_pages_node and return NULL to avoid issues further down the > callchain. > > Also update the VM_WARN_ON in __alloc_pages_node which could skip this > warn if the gfp_mask is not GFP_THISNODE. Page allocator trusts callers to know they are doing a right thing so that no unnecessary branches have to be implemented and the fast path is really optimized for performance. Allocating from an !node_online node is a bug in the caller. One that is not really that hard to make unfortunatelly but also one that is is not that common. That being said I am not really sure we want to introduce this check. > Co-developed-by: Rafael Aquini <aquini@redhat.com> > Signed-off-by: Nico Pache <npache@redhat.com> > --- > include/linux/gfp.h | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/include/linux/gfp.h b/include/linux/gfp.h > index b976c4177299..e7e18f6d0d9d 100644 > --- a/include/linux/gfp.h > +++ b/include/linux/gfp.h > @@ -565,7 +565,10 @@ static inline struct page * > __alloc_pages_node(int nid, gfp_t gfp_mask, unsigned int order) > { > VM_BUG_ON(nid < 0 || nid >= MAX_NUMNODES); > - VM_WARN_ON((gfp_mask & __GFP_THISNODE) && !node_online(nid)); > + VM_WARN_ON(!node_online(nid)); > + > + if (!node_online(nid)) > + return NULL; > > return __alloc_pages(gfp_mask, order, nid, NULL); > } > -- > 2.33.1
On 12/6/21 04:22, Michal Hocko wrote: > On Sun 05-12-21 22:33:37, Nico Pache wrote: >> We shouldn't allocate pages on a unavailable node. Add a check for this >> in __alloc_pages_node and return NULL to avoid issues further down the >> callchain. >> >> Also update the VM_WARN_ON in __alloc_pages_node which could skip this >> warn if the gfp_mask is not GFP_THISNODE. > > Page allocator trusts callers to know they are doing a right thing so > that no unnecessary branches have to be implemented and the fast path is > really optimized for performance. Allocating from an !node_online node > is a bug in the caller. One that is not really that hard to make > unfortunatelly but also one that is is not that common. Thank you for your review, That makes sense. I will drop this patch on my second posting to avoid any performance regression. Cheers, -- Nico > > That being said I am not really sure we want to introduce this check. > >> Co-developed-by: Rafael Aquini <aquini@redhat.com> >> Signed-off-by: Nico Pache <npache@redhat.com> >> --- >> include/linux/gfp.h | 5 ++++- >> 1 file changed, 4 insertions(+), 1 deletion(-) >> >> diff --git a/include/linux/gfp.h b/include/linux/gfp.h >> index b976c4177299..e7e18f6d0d9d 100644 >> --- a/include/linux/gfp.h >> +++ b/include/linux/gfp.h >> @@ -565,7 +565,10 @@ static inline struct page * >> __alloc_pages_node(int nid, gfp_t gfp_mask, unsigned int order) >> { >> VM_BUG_ON(nid < 0 || nid >= MAX_NUMNODES); >> - VM_WARN_ON((gfp_mask & __GFP_THISNODE) && !node_online(nid)); >> + VM_WARN_ON(!node_online(nid)); >> + >> + if (!node_online(nid)) >> + return NULL; >> >> return __alloc_pages(gfp_mask, order, nid, NULL); >> } >> -- >> 2.33.1 >
diff --git a/include/linux/gfp.h b/include/linux/gfp.h index b976c4177299..e7e18f6d0d9d 100644 --- a/include/linux/gfp.h +++ b/include/linux/gfp.h @@ -565,7 +565,10 @@ static inline struct page * __alloc_pages_node(int nid, gfp_t gfp_mask, unsigned int order) { VM_BUG_ON(nid < 0 || nid >= MAX_NUMNODES); - VM_WARN_ON((gfp_mask & __GFP_THISNODE) && !node_online(nid)); + VM_WARN_ON(!node_online(nid)); + + if (!node_online(nid)) + return NULL; return __alloc_pages(gfp_mask, order, nid, NULL); }
We shouldn't allocate pages on a unavailable node. Add a check for this in __alloc_pages_node and return NULL to avoid issues further down the callchain. Also update the VM_WARN_ON in __alloc_pages_node which could skip this warn if the gfp_mask is not GFP_THISNODE. Co-developed-by: Rafael Aquini <aquini@redhat.com> Signed-off-by: Nico Pache <npache@redhat.com> --- include/linux/gfp.h | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)