Commit 6f7d760e authored by Huang Ying's avatar Huang Ying Committed by Andrew Morton
Browse files

migrate_pages: move THP/hugetlb migration support check to simplify code 

This is a code cleanup patch, no functionality change is expected.  After
the change, the line number reduces especially in the long
migrate_pages_batch().

Link: https://lkml.kernel.org/r/20230213123444.155149-10-ying.huang@intel.com


Signed-off-by: default avatar"Huang, Ying" <ying.huang@intel.com>
Suggested-by: default avatarAlistair Popple <apopple@nvidia.com>
Reviewed-by: default avatarZi Yan <ziy@nvidia.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Bharata B Rao <bharata@amd.com>
Cc: Xin Hao <xhao@linux.alibaba.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 7e12beb8

mm/migrate.c

+36 −47
Original line number Diff line number Diff line
@@ -1117,9 +1117,6 @@ static int migrate_folio_unmap(new_page_t get_new_page, free_page_t put_new_page 
	bool locked = false;

	bool dst_locked = false;



	if (!thp_migration_supported() && folio_test_transhuge(src))

		return -ENOSYS;



	if (folio_ref_count(src) == 1) {

		/* Folio was freed from under us. So we are done. */

		folio_clear_active(src);
@@ -1380,16 +1377,6 @@ static int unmap_and_move_huge_page(new_page_t get_new_page, 
	struct anon_vma *anon_vma = NULL;

	struct address_space *mapping = NULL;



	/*

	 * Migratability of hugepages depends on architectures and their size.

	 * This check is necessary because some callers of hugepage migration

	 * like soft offline and memory hotremove don't walk through page

	 * tables or check whether the hugepage is pmd-based or not before

	 * kicking migration.

	 */

	if (!hugepage_migration_supported(page_hstate(hpage)))

		return -ENOSYS;



	if (folio_ref_count(src) == 1) {

		/* page was freed from under us. So we are done. */

		folio_putback_active_hugetlb(src);
@@ -1556,6 +1543,20 @@ static int migrate_hugetlbs(struct list_head *from, new_page_t get_new_page, 


			cond_resched();



			/*

			 * Migratability of hugepages depends on architectures and

			 * their size.  This check is necessary because some callers

			 * of hugepage migration like soft offline and memory

			 * hotremove don't walk through page tables or check whether

			 * the hugepage is pmd-based or not before kicking migration.

			 */

			if (!hugepage_migration_supported(folio_hstate(folio))) {

				nr_failed++;

				stats->nr_failed_pages += nr_pages;

				list_move_tail(&folio->lru, ret_folios);

				continue;

			}



			rc = unmap_and_move_huge_page(get_new_page,

						      put_new_page, private,

						      &folio->page, pass > 2, mode,
@@ -1565,16 +1566,9 @@ static int migrate_hugetlbs(struct list_head *from, new_page_t get_new_page, 
			 *	Success: hugetlb folio will be put back

			 *	-EAGAIN: stay on the from list

			 *	-ENOMEM: stay on the from list

			 *	-ENOSYS: stay on the from list

			 *	Other errno: put on ret_folios list

			 */

			switch(rc) {

			case -ENOSYS:

				/* Hugetlb migration is unsupported */

				nr_failed++;

				stats->nr_failed_pages += nr_pages;

				list_move_tail(&folio->lru, ret_folios);

				break;

			case -ENOMEM:

				/*

				 * When memory is low, don't bother to try to migrate
@@ -1664,24 +1658,9 @@ static int migrate_pages_batch(struct list_head *from, new_page_t get_new_page, 


			cond_resched();



			rc = migrate_folio_unmap(get_new_page, put_new_page, private,

						 folio, &dst, pass > 2, avoid_force_lock,

						 mode, reason, ret_folios);

			/*

			 * The rules are:

			 *	Success: folio will be freed

			 *	Unmap: folio will be put on unmap_folios list,

			 *	       dst folio put on dst_folios list

			 *	-EAGAIN: stay on the from list

			 *	-EDEADLOCK: stay on the from list

			 *	-ENOMEM: stay on the from list

			 *	-ENOSYS: stay on the from list

			 *	Other errno: put on ret_folios list

			 */

			switch(rc) {

			/*

			 * Large folio migration might be unsupported or

			 * the allocation could've failed so we should retry

			 * the allocation might be failed so we should retry

			 * on the same folio with the large folio split

			 * to normal folios.

			 *
@@ -1689,22 +1668,32 @@ static int migrate_pages_batch(struct list_head *from, new_page_t get_new_page, 
			 * we will migrate them after the rest of the

			 * list is processed.

			 */

			case -ENOSYS:

				/* Large folio migration is unsupported */

				if (is_large) {

			if (!thp_migration_supported() && is_thp) {

				nr_large_failed++;

					stats->nr_thp_failed += is_thp;

				stats->nr_thp_failed++;

				if (!try_split_folio(folio, &split_folios)) {

						stats->nr_thp_split += is_thp;

						break;

					}

				} else if (!no_split_folio_counting) {

					nr_failed++;

					stats->nr_thp_split++;

					continue;

				}



				stats->nr_failed_pages += nr_pages;

				list_move_tail(&folio->lru, ret_folios);

				break;

				continue;

			}



			rc = migrate_folio_unmap(get_new_page, put_new_page, private,

						 folio, &dst, pass > 2, avoid_force_lock,

						 mode, reason, ret_folios);

			/*

			 * The rules are:

			 *	Success: folio will be freed

			 *	Unmap: folio will be put on unmap_folios list,

			 *	       dst folio put on dst_folios list

			 *	-EAGAIN: stay on the from list

			 *	-EDEADLOCK: stay on the from list

			 *	-ENOMEM: stay on the from list

			 *	Other errno: put on ret_folios list

			 */

			switch(rc) {

			case -ENOMEM:

				/*

				 * When memory is low, don't bother to try to migrate