mm/page_alloc: don't use __GFP_HARDWALL when migrating pages via alloc_contig*()

Patch series "mm: don't use __GFP_HARDWALL when migrating remote pages".

__GFP_HARDWALL means that we will be respecting the cpuset of the caller
when allocating a page.  However, when we are migrating remote allocations
(pages allocated from other context), the cpuset of the current context is
irrelevant.

For memory offlining + alloc_contig_*(), this is rather obvious.  There
might be other such page migration users, let's start with the obvious
ones.

This patch (of 2):

We'll migrate pages allocated by other contexts; respecting the cpuset of
the alloc_contig*() caller when allocating a migration target does not
make sense.

Drop the __GFP_HARDWALL.

Note that in an ideal world, migration code could figure out the cpuset
of the original context and take that into consideration.

Link: https://lkml.kernel.org/r/20241205090508.2095225-1-david@redhat.com
Link: https://lkml.kernel.org/r/20241205090508.2095225-2-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Suggested-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index a52c602..dde19db 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -6412,11 +6412,11 @@ static int __alloc_contig_verify_gfp_mask(gfp_t gfp_mask, gfp_t *gfp_cc_mask)
         * page range. Migratable pages are movable, __GFP_MOVABLE is implied
         * for them.
         *
-        * Traditionally we always had __GFP_HARDWALL|__GFP_RETRY_MAYFAIL set,
-        * keep doing that to not degrade callers.
+        * Traditionally we always had __GFP_RETRY_MAYFAIL set, keep doing that
+        * to not degrade callers.
         */
        *gfp_cc_mask = (gfp_mask & (reclaim_mask | cc_action_mask)) |
-                       __GFP_HARDWALL | __GFP_MOVABLE | __GFP_RETRY_MAYFAIL;
+                       __GFP_MOVABLE | __GFP_RETRY_MAYFAIL;
        return 0;
 }