A small suggestion: Given that migrate_pages() requires that
*nr_succeeded should be initialized to 0 when it is called due to its
use of *nr_succeeded in count_vm_events() and trace_mm_migrate_pages(),
it would be less error-prone if migrate_pages() initializes
*nr_succeeded itself.
On Thu, Apr 1, 2021 at 11:35 AM Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> wrote:
>
>
> From: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx>
>
> The migrate_pages() returns the number of pages that were not migrated,
> or an error code. When returning an error code, there is no way to know
> how many pages were migrated or not migrated.
>
> In the following patch, migrate_pages() is used to demote pages to PMEM
> node, we need account how many pages are reclaimed (demoted) since page
> reclaim behavior depends on this. Add *nr_succeeded parameter to make
> migrate_pages() return how many pages are demoted successfully for all
> cases.
>
> Signed-off-by: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx>
> Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
> Reviewed-by: Yang Shi <shy828301@xxxxxxxxx>
> Cc: Wei Xu <weixugc@xxxxxxxxxx>
> Cc: Huang Ying <ying.huang@xxxxxxxxx>
> Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
> Cc: David Hildenbrand <david@xxxxxxxxxx>
> Cc: osalvador <osalvador@xxxxxxx>
>
> --
>
> Note: Yang Shi originally wrote the patch, thus the SoB. There was
> also a Reviewed-by provided since there were some modifications made
> to this after the original work.
>
> Changes since 20210302:
> * Fix definition of CONFIG_MIGRATION=n stub migrate_pages(). Its
> parameters were wrong, but oddly enough did not generate any
> compile errors.
>
> Changes since 20200122:
> * Fix migrate_pages() to manipulate nr_succeeded *value*
> rather than the pointer.
> ---
>
> b/include/linux/migrate.h | 5 +++--
> b/mm/compaction.c | 3 ++-
> b/mm/gup.c | 3 ++-
> b/mm/memory-failure.c | 4 +++-
> b/mm/memory_hotplug.c | 4 +++-
> b/mm/mempolicy.c | 8 ++++++--
> b/mm/migrate.c | 19 +++++++++++--------
> b/mm/page_alloc.c | 9 ++++++---
> 8 files changed, 36 insertions(+), 19 deletions(-)
>
> diff -puN include/linux/migrate.h~migrate_pages-add-success-return include/linux/migrate.h
> --- a/include/linux/migrate.h~migrate_pages-add-success-return 2021-03-31 15:17:14.144000255 -0700
> +++ b/include/linux/migrate.h 2021-03-31 15:17:14.182000255 -0700
> @@ -40,7 +40,8 @@ extern int migrate_page(struct address_s
> struct page *newpage, struct page *page,
> enum migrate_mode mode);
> extern int migrate_pages(struct list_head *l, new_page_t new, free_page_t free,
> - unsigned long private, enum migrate_mode mode, int reason);
> + unsigned long private, enum migrate_mode mode, int reason,
> + unsigned int *nr_succeeded);
> extern struct page *alloc_migration_target(struct page *page, unsigned long private);
> extern int isolate_movable_page(struct page *page, isolate_mode_t mode);
> extern void putback_movable_page(struct page *page);
> @@ -58,7 +59,7 @@ extern int migrate_page_move_mapping(str
> static inline void putback_movable_pages(struct list_head *l) {}
> static inline int migrate_pages(struct list_head *l, new_page_t new,
> free_page_t free, unsigned long private, enum migrate_mode mode,
> - int reason)
> + int reason, unsigned int *nr_succeeded)
> { return -ENOSYS; }
> static inline struct page *alloc_migration_target(struct page *page,
> unsigned long private)
> diff -puN mm/compaction.c~migrate_pages-add-success-return mm/compaction.c
> --- a/mm/compaction.c~migrate_pages-add-success-return 2021-03-31 15:17:14.146000255 -0700
> +++ b/mm/compaction.c 2021-03-31 15:17:14.186000255 -0700
> @@ -2247,6 +2247,7 @@ compact_zone(struct compact_control *cc,
> unsigned long last_migrated_pfn;
> const bool sync = cc->mode != MIGRATE_ASYNC;
> bool update_cached;
> + unsigned int nr_succeeded = 0;
>
> /*
> * These counters track activities during zone compaction. Initialize
> @@ -2364,7 +2365,7 @@ compact_zone(struct compact_control *cc,
>
> err = migrate_pages(&cc->migratepages, compaction_alloc,
> compaction_free, (unsigned long)cc, cc->mode,
> - MR_COMPACTION);
> + MR_COMPACTION, &nr_succeeded);
>
> trace_mm_compaction_migratepages(cc->nr_migratepages, err,
> &cc->migratepages);
> diff -puN mm/gup.c~migrate_pages-add-success-return mm/gup.c
> --- a/mm/gup.c~migrate_pages-add-success-return 2021-03-31 15:17:14.150000255 -0700
> +++ b/mm/gup.c 2021-03-31 15:17:14.190000255 -0700
> @@ -1550,6 +1550,7 @@ static long check_and_migrate_cma_pages(
> unsigned long i;
> unsigned long step;
> bool drain_allow = true;
> + unsigned int nr_succeeded = 0;
> bool migrate_allow = true;
> LIST_HEAD(cma_page_list);
> long ret = nr_pages;
> @@ -1606,7 +1607,7 @@ check_again:
> put_page(pages[i]);
>
> if (migrate_pages(&cma_page_list, alloc_migration_target, NULL,
> - (unsigned long)&mtc, MIGRATE_SYNC, MR_CONTIG_RANGE)) {
> + (unsigned long)&mtc, MIGRATE_SYNC, MR_CONTIG_RANGE, &nr_succeeded)) {
> /*
> * some of the pages failed migration. Do get_user_pages
> * without migration.
> diff -puN mm/memory-failure.c~migrate_pages-add-success-return mm/memory-failure.c
> --- a/mm/memory-failure.c~migrate_pages-add-success-return 2021-03-31 15:17:14.155000255 -0700
> +++ b/mm/memory-failure.c 2021-03-31 15:17:14.194000255 -0700
> @@ -1809,6 +1809,7 @@ static int __soft_offline_page(struct pa
> unsigned long pfn = page_to_pfn(page);
> struct page *hpage = compound_head(page);
> char const *msg_page[] = {"page", "hugepage"};
> + unsigned int nr_succeeded = 0;
> bool huge = PageHuge(page);
> LIST_HEAD(pagelist);
> struct migration_target_control mtc = {
> @@ -1852,7 +1853,8 @@ static int __soft_offline_page(struct pa
>
> if (isolate_page(hpage, &pagelist)) {
> ret = migrate_pages(&pagelist, alloc_migration_target, NULL,
> - (unsigned long)&mtc, MIGRATE_SYNC, MR_MEMORY_FAILURE);
> + (unsigned long)&mtc, MIGRATE_SYNC, MR_MEMORY_FAILURE,
> + &nr_succeeded);
> if (!ret) {
> bool release = !huge;
>
> diff -puN mm/memory_hotplug.c~migrate_pages-add-success-return mm/memory_hotplug.c
> --- a/mm/memory_hotplug.c~migrate_pages-add-success-return 2021-03-31 15:17:14.160000255 -0700
> +++ b/mm/memory_hotplug.c 2021-03-31 15:17:14.197000255 -0700
> @@ -1392,6 +1392,7 @@ do_migrate_range(unsigned long start_pfn
> unsigned long pfn;
> struct page *page, *head;
> int ret = 0;
> + unsigned int nr_succeeded = 0;
> LIST_HEAD(source);
>
> for (pfn = start_pfn; pfn < end_pfn; pfn++) {
> @@ -1466,7 +1467,8 @@ do_migrate_range(unsigned long start_pfn
> if (nodes_empty(nmask))
> node_set(mtc.nid, nmask);
> ret = migrate_pages(&source, alloc_migration_target, NULL,
> - (unsigned long)&mtc, MIGRATE_SYNC, MR_MEMORY_HOTPLUG);
> + (unsigned long)&mtc, MIGRATE_SYNC, MR_MEMORY_HOTPLUG,
> + &nr_succeeded);
> if (ret) {
> list_for_each_entry(page, &source, lru) {
> pr_warn("migrating pfn %lx failed ret:%d ",
> diff -puN mm/mempolicy.c~migrate_pages-add-success-return mm/mempolicy.c
> --- a/mm/mempolicy.c~migrate_pages-add-success-return 2021-03-31 15:17:14.163000255 -0700
> +++ b/mm/mempolicy.c 2021-03-31 15:17:14.203000255 -0700
> @@ -1081,6 +1081,7 @@ static int migrate_page_add(struct page
> static int migrate_to_node(struct mm_struct *mm, int source, int dest,
> int flags)
> {
> + unsigned int nr_succeeded = 0;
> nodemask_t nmask;
> LIST_HEAD(pagelist);
> int err = 0;
> @@ -1103,7 +1104,8 @@ static int migrate_to_node(struct mm_str
>
> if (!list_empty(&pagelist)) {
> err = migrate_pages(&pagelist, alloc_migration_target, NULL,
> - (unsigned long)&mtc, MIGRATE_SYNC, MR_SYSCALL);
> + (unsigned long)&mtc, MIGRATE_SYNC, MR_SYSCALL,
> + &nr_succeeded);
> if (err)
> putback_movable_pages(&pagelist);
> }
> @@ -1278,6 +1280,7 @@ static long do_mbind(unsigned long start
> nodemask_t *nmask, unsigned long flags)
> {
> struct mm_struct *mm = current->mm;
> + unsigned int nr_succeeded = 0;
> struct mempolicy *new;
> unsigned long end;
> int err;
> @@ -1355,7 +1358,8 @@ static long do_mbind(unsigned long start
> if (!list_empty(&pagelist)) {
> WARN_ON_ONCE(flags & MPOL_MF_LAZY);
> nr_failed = migrate_pages(&pagelist, new_page, NULL,
> - start, MIGRATE_SYNC, MR_MEMPOLICY_MBIND);
> + start, MIGRATE_SYNC, MR_MEMPOLICY_MBIND,
> + &nr_succeeded);
> if (nr_failed)
> putback_movable_pages(&pagelist);
> }
> diff -puN mm/migrate.c~migrate_pages-add-success-return mm/migrate.c
> --- a/mm/migrate.c~migrate_pages-add-success-return 2021-03-31 15:17:14.168000255 -0700
> +++ b/mm/migrate.c 2021-03-31 15:17:14.207000255 -0700
> @@ -1493,6 +1493,7 @@ static inline int try_split_thp(struct p
> * @mode: The migration mode that specifies the constraints for
> * page migration, if any.
> * @reason: The reason for page migration.
> + * @nr_succeeded: The number of pages migrated successfully.
> *
> * The function returns after 10 attempts or if no pages are movable any more
> * because the list has become empty or no retryable pages exist any more.
> @@ -1503,12 +1504,11 @@ static inline int try_split_thp(struct p
> */
> int migrate_pages(struct list_head *from, new_page_t get_new_page,
> free_page_t put_new_page, unsigned long private,
> - enum migrate_mode mode, int reason)
> + enum migrate_mode mode, int reason, unsigned int *nr_succeeded)
> {
> int retry = 1;
> int thp_retry = 1;
> int nr_failed = 0;
> - int nr_succeeded = 0;
> int nr_thp_succeeded = 0;
> int nr_thp_failed = 0;
> int nr_thp_split = 0;
> @@ -1611,10 +1611,10 @@ retry:
> case MIGRATEPAGE_SUCCESS:
> if (is_thp) {
> nr_thp_succeeded++;
> - nr_succeeded += nr_subpages;
> + *nr_succeeded += nr_subpages;
> break;
> }
> - nr_succeeded++;
> + (*nr_succeeded)++;
> break;
> default:
> /*
> @@ -1643,12 +1643,12 @@ out:
> */
> list_splice(&ret_pages, from);
>
> - count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded);
> + count_vm_events(PGMIGRATE_SUCCESS, *nr_succeeded);
> count_vm_events(PGMIGRATE_FAIL, nr_failed);
> count_vm_events(THP_MIGRATION_SUCCESS, nr_thp_succeeded);
> count_vm_events(THP_MIGRATION_FAIL, nr_thp_failed);
> count_vm_events(THP_MIGRATION_SPLIT, nr_thp_split);
> - trace_mm_migrate_pages(nr_succeeded, nr_failed, nr_thp_succeeded,
> + trace_mm_migrate_pages(*nr_succeeded, nr_failed, nr_thp_succeeded,
> nr_thp_failed, nr_thp_split, mode, reason);
>
> if (!swapwrite)
> @@ -1716,6 +1716,7 @@ static int store_status(int __user *stat
> static int do_move_pages_to_node(struct mm_struct *mm,
> struct list_head *pagelist, int node)
> {
> + unsigned int nr_succeeded = 0;
> int err;
> struct migration_target_control mtc = {
> .nid = node,
> @@ -1723,7 +1724,8 @@ static int do_move_pages_to_node(struct
> };
>
> err = migrate_pages(pagelist, alloc_migration_target, NULL,
> - (unsigned long)&mtc, MIGRATE_SYNC, MR_SYSCALL);
> + (unsigned long)&mtc, MIGRATE_SYNC, MR_SYSCALL,
> + &nr_succeeded);
> if (err)
> putback_movable_pages(pagelist);
> return err;
> @@ -2207,6 +2209,7 @@ int migrate_misplaced_page(struct page *
> pg_data_t *pgdat = NODE_DATA(node);
> int isolated;
> int nr_remaining;
> + unsigned int nr_succeeded = 0;
> LIST_HEAD(migratepages);
>
> /*
> @@ -2230,7 +2233,7 @@ int migrate_misplaced_page(struct page *
> list_add(&page->lru, &migratepages);
> nr_remaining = migrate_pages(&migratepages, alloc_misplaced_dst_page,
> NULL, node, MIGRATE_ASYNC,
> - MR_NUMA_MISPLACED);
> + MR_NUMA_MISPLACED, &nr_succeeded);
> if (nr_remaining) {
> if (!list_empty(&migratepages)) {
> list_del(&page->lru);
> diff -puN mm/page_alloc.c~migrate_pages-add-success-return mm/page_alloc.c
> --- a/mm/page_alloc.c~migrate_pages-add-success-return 2021-03-31 15:17:14.178000255 -0700
> +++ b/mm/page_alloc.c 2021-03-31 15:17:14.213000255 -0700
> @@ -8452,7 +8452,8 @@ static unsigned long pfn_max_align_up(un
>
> /* [start, end) must belong to a single zone. */
> static int __alloc_contig_migrate_range(struct compact_control *cc,
> - unsigned long start, unsigned long end)
> + unsigned long start, unsigned long end,
> + unsigned int *nr_succeeded)
> {
> /* This function is based on compact_zone() from compaction.c. */
> unsigned int nr_reclaimed;
> @@ -8490,7 +8491,8 @@ static int __alloc_contig_migrate_range(
> cc->nr_migratepages -= nr_reclaimed;
>
> ret = migrate_pages(&cc->migratepages, alloc_migration_target,
> - NULL, (unsigned long)&mtc, cc->mode, MR_CONTIG_RANGE);
> + NULL, (unsigned long)&mtc, cc->mode, MR_CONTIG_RANGE,
> + nr_succeeded);
> }
> if (ret < 0) {
> putback_movable_pages(&cc->migratepages);
> @@ -8526,6 +8528,7 @@ int alloc_contig_range(unsigned long sta
> unsigned long outer_start, outer_end;
> unsigned int order;
> int ret = 0;
> + unsigned int nr_succeeded = 0;
>
> struct compact_control cc = {
> .nr_migratepages = 0,
> @@ -8580,7 +8583,7 @@ int alloc_contig_range(unsigned long sta
> * allocated. So, if we fall through be sure to clear ret so that
> * -EBUSY is not accidentally used or returned to caller.
> */
> - ret = __alloc_contig_migrate_range(&cc, start, end);
> + ret = __alloc_contig_migrate_range(&cc, start, end, &nr_succeeded);
> if (ret && ret != -EBUSY)
> goto done;
> ret =0;
> _
