This is a note to let you know that I've just added the patch titled
mm/page_alloc: explicitly record high-order atomic allocations in alloc_flags
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mm-page_alloc-explicitly-record-high-order-atomic-al.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 033cc55389ad1443530b5b69b70d07760aee696e
Author: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Date: Fri Jan 13 11:12:14 2023 +0000
mm/page_alloc: explicitly record high-order atomic allocations in alloc_flags
[ Upstream commit eb2e2b425c6984ca8034448a3f2c680622bd3d4d ]
A high-order ALLOC_HARDER allocation is assumed to be atomic. While that
is accurate, it changes later in the series. In preparation, explicitly
record high-order atomic allocations in gfp_to_alloc_flags().
Link: https://lkml.kernel.org/r/20230113111217.14134-4-mgorman@xxxxxxxxxxxxxxxxxxx
Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: NeilBrown <neilb@xxxxxxx>
Cc: Thierry Reding <thierry.reding@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Stable-dep-of: 281dd25c1a01 ("mm/page_alloc: let GFP_ATOMIC order-0 allocs access highatomic reserves")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/mm/internal.h b/mm/internal.h
index e6c96327b5855..136f435e0f1ab 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -603,6 +603,7 @@ unsigned int reclaim_clean_pages_from_list(struct zone *zone,
#else
#define ALLOC_NOFRAGMENT 0x0
#endif
+#define ALLOC_HIGHATOMIC 0x200 /* Allows access to MIGRATE_HIGHATOMIC */
#define ALLOC_KSWAPD 0x800 /* allow waking of kswapd, __GFP_KSWAPD_RECLAIM set */
enum ttu_flags;
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 72835cf4034bc..43122de999c4c 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3614,10 +3614,20 @@ struct page *rmqueue_buddy(struct zone *preferred_zone, struct zone *zone,
* reserved for high-order atomic allocation, so order-0
* request should skip it.
*/
- if (order > 0 && alloc_flags & ALLOC_HARDER)
+ if (alloc_flags & ALLOC_HIGHATOMIC)
page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC);
if (!page) {
page = __rmqueue(zone, order, migratetype, alloc_flags);
+
+ /*
+ * If the allocation fails, allow OOM handling access
+ * to HIGHATOMIC reserves as failing now is worse than
+ * failing a high-order atomic allocation in the
+ * future.
+ */
+ if (!page && (alloc_flags & ALLOC_OOM))
+ page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC);
+
if (!page) {
spin_unlock_irqrestore(&zone->lock, flags);
return NULL;
@@ -3912,8 +3922,10 @@ bool __zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark,
return true;
}
#endif
- if (alloc_harder && !free_area_empty(area, MIGRATE_HIGHATOMIC))
+ if ((alloc_flags & (ALLOC_HIGHATOMIC|ALLOC_OOM)) &&
+ !free_area_empty(area, MIGRATE_HIGHATOMIC)) {
return true;
+ }
}
return false;
}
@@ -4172,7 +4184,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
* If this is a high-order atomic allocation then check
* if the pageblock should be reserved for the future
*/
- if (unlikely(order && (alloc_flags & ALLOC_HARDER)))
+ if (unlikely(alloc_flags & ALLOC_HIGHATOMIC))
reserve_highatomic_pageblock(page, zone, order);
return page;
@@ -4691,7 +4703,7 @@ static void wake_all_kswapds(unsigned int order, gfp_t gfp_mask,
}
static inline unsigned int
-gfp_to_alloc_flags(gfp_t gfp_mask)
+gfp_to_alloc_flags(gfp_t gfp_mask, unsigned int order)
{
unsigned int alloc_flags = ALLOC_WMARK_MIN | ALLOC_CPUSET;
@@ -4717,8 +4729,13 @@ gfp_to_alloc_flags(gfp_t gfp_mask)
* Not worth trying to allocate harder for __GFP_NOMEMALLOC even
* if it can't schedule.
*/
- if (!(gfp_mask & __GFP_NOMEMALLOC))
+ if (!(gfp_mask & __GFP_NOMEMALLOC)) {
alloc_flags |= ALLOC_HARDER;
+
+ if (order > 0)
+ alloc_flags |= ALLOC_HIGHATOMIC;
+ }
+
/*
* Ignore cpuset mems for GFP_ATOMIC rather than fail, see the
* comment for __cpuset_node_allowed().
@@ -4946,7 +4963,7 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
* kswapd needs to be woken up, and to avoid the cost of setting up
* alloc_flags precisely. So we do that now.
*/
- alloc_flags = gfp_to_alloc_flags(gfp_mask);
+ alloc_flags = gfp_to_alloc_flags(gfp_mask, order);
/*
* We need to recalculate the starting point for the zonelist iterator
