mm: record the migration reason for struct migration_target_control

Patch series "make the hugetlb migration strategy consistent", v2.

As discussed in previous thread [1], there is an inconsistency when
handling hugetlb migration.  When handling the migration of freed hugetlb,
it prevents fallback to other NUMA nodes in
alloc_and_dissolve_hugetlb_folio().  However, when dealing with in-use
hugetlb, it allows fallback to other NUMA nodes in
alloc_hugetlb_folio_nodemask(), which can break the per-node hugetlb pool
and might result in unexpected failures when node bound workloads doesn't
get what is asssumed available.

This patchset tries to make the hugetlb migration strategy more clear
and consistent. Please find details in each patch.

[1]
https://lore.kernel.org/all/6f26ce22d2fcd523418a085f2c588fe0776d46e7.1706794035.git.baolin.wang@linux.alibaba.com/


This patch (of 2):

To support different hugetlb allocation strategies during hugetlb
migration based on various migration reasons, record the migration reason
in the migration_target_control structure as a preparation.

Link: https://lkml.kernel.org/r/cover.1709719720.git.baolin.wang@linux.alibaba.com
Link: https://lkml.kernel.org/r/7b95d4981e07211f57139fc5b1f7ce91b920cee4.1709719720.git.baolin.wang@linux.alibaba.com
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: David Hildenbrand <david@redhat.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/gup.c

@@ -2145,6 +2145,7 @@ static int migrate_longterm_unpinnable_pages(
 		struct migration_target_control mtc = {
 			.nid = NUMA_NO_NODE,
 			.gfp_mask = GFP_USER | __GFP_NOWARN,
+			.reason = MR_LONGTERM_PIN,
 		};
 
 		if (migrate_pages(movable_page_list, alloc_migration_target,

mm/internal.h

@@ -1045,6 +1045,7 @@ struct migration_target_control {
 	int nid;		/* preferred node id */
 	nodemask_t *nmask;
 	gfp_t gfp_mask;
+	enum migrate_reason reason;
 };
 
 /*

mm/memory-failure.c

@@ -2669,6 +2669,7 @@ static int soft_offline_in_use_page(struct page *page)
 	struct migration_target_control mtc = {
 		.nid = NUMA_NO_NODE,
 		.gfp_mask = GFP_USER | __GFP_MOVABLE | __GFP_RETRY_MAYFAIL,
+		.reason = MR_MEMORY_FAILURE,
 	};
 
 	if (!huge && folio_test_large(folio)) {

mm/memory_hotplug.c

@@ -1841,6 +1841,7 @@ static void do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
 		struct migration_target_control mtc = {
 			.nmask = &nmask,
 			.gfp_mask = GFP_USER | __GFP_MOVABLE | __GFP_RETRY_MAYFAIL,
+			.reason = MR_MEMORY_HOTPLUG,
 		};
 		int ret;
 

mm/mempolicy.c

@@ -1070,6 +1070,7 @@ static long migrate_to_node(struct mm_struct *mm, int source, int dest,
 	struct migration_target_control mtc = {
 		.nid = dest,
 		.gfp_mask = GFP_HIGHUSER_MOVABLE | __GFP_THISNODE,
+		.reason = MR_SYSCALL,
 	};
 
 	nodes_clear(nmask);

mm/migrate.c

@@ -2060,6 +2060,7 @@ static int do_move_pages_to_node(struct list_head *pagelist, int node)
 	struct migration_target_control mtc = {
 		.nid = node,
 		.gfp_mask = GFP_HIGHUSER_MOVABLE | __GFP_THISNODE,
+		.reason = MR_SYSCALL,
 	};
 
 	err = migrate_pages(pagelist, alloc_migration_target, NULL,

mm/page_alloc.c

@@ -6351,6 +6351,7 @@ int __alloc_contig_migrate_range(struct compact_control *cc,
 	struct migration_target_control mtc = {
 		.nid = zone_to_nid(cc->zone),
 		.gfp_mask = GFP_USER | __GFP_MOVABLE | __GFP_RETRY_MAYFAIL,
+		.reason = MR_CONTIG_RANGE,
 	};
 	struct page *page;
 	unsigned long total_mapped = 0;

mm/vmscan.c

@@ -967,7 +967,8 @@ static unsigned int demote_folio_list(struct list_head *demote_folios,
 		.gfp_mask = (GFP_HIGHUSER_MOVABLE & ~__GFP_RECLAIM) | __GFP_NOWARN |
 			__GFP_NOMEMALLOC | GFP_NOWAIT,
 		.nid = target_nid,
-		.nmask = &allowed_mask
+		.nmask = &allowed_mask,
+		.reason = MR_DEMOTION,
 	};
 
 	if (list_empty(demote_folios))