Obviously we only support order <= 1 __GFP_NOFAIL allocation and if
someone wants larger memory, they should consider using kvmalloc()
instead.
Suggested-by: David Hildenbrand <david@xxxxxxxxxx>
Suggested-by: Michal Hocko <mhocko@xxxxxxxx>
Signed-off-by: Barry Song <v-songbaohua@xxxxxxxx>
---
include/linux/gfp_types.h | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/include/linux/gfp_types.h b/include/linux/gfp_types.h
index 4a1fa7706b0c..65db9349f905 100644
--- a/include/linux/gfp_types.h
+++ b/include/linux/gfp_types.h
@@ -253,7 +253,8 @@ enum {
* used only when there is no reasonable failure policy) but it is
* definitely preferable to use the flag rather than opencode endless
* loop around allocator.
- * Using this flag for costly allocations is _highly_ discouraged.
+ * Allocating pages from the buddy with __GFP_NOFAIL and order > 1 is
+ * not supported. Please consider using kvmalloc() instead.
*/
#define __GFP_IO ((__force gfp_t)___GFP_IO)
#define __GFP_FS ((__force gfp_t)___GFP_FS)
--
2.34.1
>
> > ---
> > Â mm/page_alloc.c | 50 ++++++++++++++++++++++++-------------------------
> > Â 1 file changed, 25 insertions(+), 25 deletions(-)
> >
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index c81ee5662cc7..e790b4227322 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -3033,12 +3033,6 @@ struct page *rmqueue(struct zone *preferred_zone,
> > Â {
> > Â Â Â struct page *page;
> >
> > - Â Â /*
> > - Â Â Â * We most definitely don't want callers attempting to
> > - Â Â Â * allocate greater than order-1 page units with __GFP_NOFAIL.
> > - Â Â Â */
> > - Â Â WARN_ON_ONCE((gfp_flags & __GFP_NOFAIL) && (order > 1));
> > -
> > Â Â Â if (likely(pcp_allowed_order(order))) {
> > Â Â Â Â Â Â Â page = rmqueue_pcplist(preferred_zone, zone, order,
> > Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â migratetype, alloc_flags);
> > @@ -4175,6 +4169,7 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
> > Â {
> > Â Â Â bool can_direct_reclaim = gfp_mask & __GFP_DIRECT_RECLAIM;
> > Â Â Â bool can_compact = gfp_compaction_allowed(gfp_mask);
> > + Â Â bool nofail = gfp_mask & __GFP_NOFAIL;
> > Â Â Â const bool costly_order = order > PAGE_ALLOC_COSTLY_ORDER;
> > Â Â Â struct page *page = NULL;
> > Â Â Â unsigned int alloc_flags;
> > @@ -4187,6 +4182,25 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
> > Â Â Â unsigned int zonelist_iter_cookie;
> > Â Â Â int reserve_flags;
> >
> > + Â Â if (unlikely(nofail)) {
> > + Â Â Â Â Â Â /*
> > + Â Â Â Â Â Â Â * We most definitely don't want callers attempting to
> > + Â Â Â Â Â Â Â * allocate greater than order-1 page units with __GFP_NOFAIL.
> > + Â Â Â Â Â Â Â */
> > + Â Â Â Â Â Â WARN_ON_ONCE(order > 1);
> > + Â Â Â Â Â Â /*
> > + Â Â Â Â Â Â Â * Also we don't support __GFP_NOFAIL without __GFP_DIRECT_RECLAIM,
> > + Â Â Â Â Â Â Â * otherwise, we may result in lockup.
> > + Â Â Â Â Â Â Â */
> > + Â Â Â Â Â Â WARN_ON_ONCE(!can_direct_reclaim);
> > + Â Â Â Â Â Â /*
> > + Â Â Â Â Â Â Â * PF_MEMALLOC request from this context is rather bizarre
> > + Â Â Â Â Â Â Â * because we cannot reclaim anything and only can loop waiting
> > + Â Â Â Â Â Â Â * for somebody to do a work for us.
> > + Â Â Â Â Â Â Â */
> > + Â Â Â Â Â Â WARN_ON_ONCE(current->flags & PF_MEMALLOC);
> > + Â Â }
> > +
> > Â restart:
> > Â Â Â compaction_retries = 0;
> > Â Â Â no_progress_loops = 0;
> > @@ -4404,29 +4418,15 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
> > Â Â Â Â * Make sure that __GFP_NOFAIL request doesn't leak out and make sure
> > Â Â Â Â * we always retry
> > Â Â Â Â */
> > - Â Â if (gfp_mask & __GFP_NOFAIL) {
> > + Â Â if (unlikely(nofail)) {
> > Â Â Â Â Â Â Â /*
> > - Â Â Â Â Â Â Â * All existing users of the __GFP_NOFAIL are blockable, so warn
> > - Â Â Â Â Â Â Â * of any new users that actually require GFP_NOWAIT
> > + Â Â Â Â Â Â Â * Lacking direct_reclaim we can't do anything to reclaim memory,
> > + Â Â Â Â Â Â Â * we disregard these unreasonable nofail requests and still
> > + Â Â Â Â Â Â Â * return NULL
> > Â Â Â Â Â Â Â Â */
> > - Â Â Â Â Â Â if (WARN_ON_ONCE_GFP(!can_direct_reclaim, gfp_mask))
> > + Â Â Â Â Â Â if (!can_direct_reclaim)
> > Â Â Â Â Â Â Â Â Â Â Â goto fail;
> >
> > - Â Â Â Â Â Â /*
> > - Â Â Â Â Â Â Â * PF_MEMALLOC request from this context is rather bizarre
> > - Â Â Â Â Â Â Â * because we cannot reclaim anything and only can loop waiting
> > - Â Â Â Â Â Â Â * for somebody to do a work for us
> > - Â Â Â Â Â Â Â */
> > - Â Â Â Â Â Â WARN_ON_ONCE_GFP(current->flags & PF_MEMALLOC, gfp_mask);
> > -
> > - Â Â Â Â Â Â /*
> > - Â Â Â Â Â Â Â * non failing costly orders are a hard requirement which we
> > - Â Â Â Â Â Â Â * are not prepared for much so let's warn about these users
> > - Â Â Â Â Â Â Â * so that we can identify them and convert them to something
> > - Â Â Â Â Â Â Â * else.
> > - Â Â Â Â Â Â Â */
> > - Â Â Â Â Â Â WARN_ON_ONCE_GFP(costly_order, gfp_mask);
> > -
> > Â Â Â Â Â Â Â /*
> > Â Â Â Â Â Â Â Â * Help non-failing allocations by giving some access to memory
> > Â Â Â Â Â Â Â Â * reserves normally used for high priority non-blocking
> > --
> > 2.34.1
>
> --
> Michal Hocko
> SUSE Labs
Thanks
Barry
