Re: [PATCH] mm: Code cleanup for MADV_FREE

From: Pankaj Gupta
Date: Mon Mar 16 2020 - 01:54:33 EST

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>
> From: Huang Ying <ying.huang@xxxxxxxxx>
>
> Some comments for MADV_FREE is revised and added to help people understand the
> MADV_FREE code, especially the page flag, PG_swapbacked. This makes
> page_is_file_cache() isn't consistent with its comments. So the function is
> renamed to page_is_file_lru() to make them consistent again. All these are put
> in one patch as one logical change.
>
> Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
> Suggested-by: David Hildenbrand <david@xxxxxxxxxx>
> Suggested-by: Johannes Weiner <hannes@xxxxxxxxxxx>
> Suggested-by: David Rientjes <rientjes@xxxxxxxxxx>
> Cc: Michal Hocko <mhocko@xxxxxxxxxx>
> Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
> Cc: Mel Gorman <mgorman@xxxxxxx>
> Cc: Vlastimil Babka <vbabka@xxxxxxx>
> Cc: Minchan Kim <minchan@xxxxxxxxxx>
> Cc: Hugh Dickins <hughd@xxxxxxxxxx>
> Cc: Rik van Riel <riel@xxxxxxxxxxx>
> ---
> include/linux/mm_inline.h | 15 ++++++++-------
> include/linux/page-flags.h | 4 ++++
> include/trace/events/vmscan.h | 2 +-
> mm/compaction.c | 2 +-
> mm/gup.c | 2 +-
> mm/khugepaged.c | 4 ++--
> mm/memory-failure.c | 2 +-
> mm/memory_hotplug.c | 2 +-
> mm/mempolicy.c | 2 +-
> mm/migrate.c | 16 ++++++++--------
> mm/mprotect.c | 2 +-
> mm/swap.c | 16 ++++++++--------
> mm/vmscan.c | 12 ++++++------
> 13 files changed, 43 insertions(+), 38 deletions(-)
>
> diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h
> index 6f2fef7b0784..9aea990069a2 100644
> --- a/include/linux/mm_inline.h
> +++ b/include/linux/mm_inline.h
> @@ -6,19 +6,20 @@
> #include <linux/swap.h>
>
> /**
> - * page_is_file_cache - should the page be on a file LRU or anon LRU?
> + * page_is_file_lru - should the page be on a file LRU or anon LRU?
> * @page: the page to test
> *
> - * Returns 1 if @page is page cache page backed by a regular filesystem,
> - * or 0 if @page is anonymous, tmpfs or otherwise ram or swap backed.
> - * Used by functions that manipulate the LRU lists, to sort a page
> - * onto the right LRU list.
> + * Returns 1 if @page is page cache page backed by a regular filesystem or
> + * anonymous page lazily freed (e.g. via MADV_FREE). Returns 0 if @page is
> + * normal anonymous page, tmpfs or otherwise ram or swap backed. Used by
> + * functions that manipulate the LRU lists, to sort a page onto the right LRU
> + * list.
> *
> * We would like to get this info without a page flag, but the state
> * needs to survive until the page is last deleted from the LRU, which
> * could be as far down as __page_cache_release.
> */
> -static inline int page_is_file_cache(struct page *page)
> +static inline int page_is_file_lru(struct page *page)
> {
> return !PageSwapBacked(page);
> }
> @@ -75,7 +76,7 @@ static __always_inline void del_page_from_lru_list(struct page *page,
> */
> static inline enum lru_list page_lru_base_type(struct page *page)
> {
> - if (page_is_file_cache(page))
> + if (page_is_file_lru(page))
> return LRU_INACTIVE_FILE;
> return LRU_INACTIVE_ANON;
> }
> diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
> index d4771b1a1232..d7a8255d6b03 100644
> --- a/include/linux/page-flags.h
> +++ b/include/linux/page-flags.h
> @@ -63,6 +63,10 @@
> * page_waitqueue(page) is a wait queue of all tasks waiting for the page
> * to become unlocked.
> *
> + * PG_swapbacked is cleared if the page is page cache page backed by a regular
> + * file system or anonymous page lazily freed (e.g. via MADV_FREE). It is set
> + * if the page is normal anonymous page, tmpfs or otherwise RAM or swap backed.
> + *
> * PG_uptodate tells whether the page's contents is valid. When a read
> * completes, the page becomes uptodate, unless a disk I/O error happened.
> *
> diff --git a/include/trace/events/vmscan.h b/include/trace/events/vmscan.h
> index a5ab2973e8dc..74bb594ccb25 100644
> --- a/include/trace/events/vmscan.h
> +++ b/include/trace/events/vmscan.h
> @@ -323,7 +323,7 @@ TRACE_EVENT(mm_vmscan_writepage,
> TP_fast_assign(
> __entry->pfn = page_to_pfn(page);
> __entry->reclaim_flags = trace_reclaim_flags(
> - page_is_file_cache(page));
> + page_is_file_lru(page));
> ),
>
> TP_printk("page=%p pfn=%lu flags=%s",
> diff --git a/mm/compaction.c b/mm/compaction.c
> index 827d8a2b3164..e8c84c6d4267 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -990,7 +990,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
> /* Successfully isolated */
> del_page_from_lru_list(page, lruvec, page_lru(page));
> mod_node_page_state(page_pgdat(page),
> - NR_ISOLATED_ANON + page_is_file_cache(page),
> + NR_ISOLATED_ANON + page_is_file_lru(page),
> hpage_nr_pages(page));
>
> isolate_success:
> diff --git a/mm/gup.c b/mm/gup.c
> index e8aaa40c35ea..411cb09b4be3 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -1691,7 +1691,7 @@ static long check_and_migrate_cma_pages(struct task_struct *tsk,
> list_add_tail(&head->lru, &cma_page_list);
> mod_node_page_state(page_pgdat(head),
> NR_ISOLATED_ANON +
> - page_is_file_cache(head),
> + page_is_file_lru(head),
> hpage_nr_pages(head));
> }
> }
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index d0ce22fb58d2..e8709e19beea 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -514,7 +514,7 @@ void __khugepaged_exit(struct mm_struct *mm)
>
> static void release_pte_page(struct page *page)
> {
> - dec_node_page_state(page, NR_ISOLATED_ANON + page_is_file_cache(page));
> + dec_node_page_state(page, NR_ISOLATED_ANON + page_is_file_lru(page));
> unlock_page(page);
> putback_lru_page(page);
> }
> @@ -614,7 +614,7 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
> goto out;
> }
> inc_node_page_state(page,
> - NR_ISOLATED_ANON + page_is_file_cache(page));
> + NR_ISOLATED_ANON + page_is_file_lru(page));
> VM_BUG_ON_PAGE(!PageLocked(page), page);
> VM_BUG_ON_PAGE(PageLRU(page), page);
>
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 1c961cd26c0b..a96364be8ab4 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1810,7 +1810,7 @@ static int __soft_offline_page(struct page *page, int flags)
> */
> if (!__PageMovable(page))
> inc_node_page_state(page, NR_ISOLATED_ANON +
> - page_is_file_cache(page));
> + page_is_file_lru(page));
> list_add(&page->lru, &pagelist);
> ret = migrate_pages(&pagelist, new_page, NULL, MPOL_MF_MOVE_ALL,
> MIGRATE_SYNC, MR_MEMORY_FAILURE);
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 8bdf484241de..e3b2074ef30c 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1324,7 +1324,7 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
> list_add_tail(&page->lru, &source);
> if (!__PageMovable(page))
> inc_node_page_state(page, NR_ISOLATED_ANON +
> - page_is_file_cache(page));
> + page_is_file_lru(page));
>
> } else {
> pr_warn("failed to isolate pfn %lx\n", pfn);
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 0c6fbee1ea5a..2c41923892f7 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -1048,7 +1048,7 @@ static int migrate_page_add(struct page *page, struct list_head *pagelist,
> if (!isolate_lru_page(head)) {
> list_add_tail(&head->lru, pagelist);
> mod_node_page_state(page_pgdat(head),
> - NR_ISOLATED_ANON + page_is_file_cache(head),
> + NR_ISOLATED_ANON + page_is_file_lru(head),
> hpage_nr_pages(head));
> } else if (flags & MPOL_MF_STRICT) {
> /*
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 8f62089126ad..de23507f5c68 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -193,7 +193,7 @@ void putback_movable_pages(struct list_head *l)
> put_page(page);
> } else {
> mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON +
> - page_is_file_cache(page), -hpage_nr_pages(page));
> + page_is_file_lru(page), -hpage_nr_pages(page));
> putback_lru_page(page);
> }
> }
> @@ -1223,7 +1223,7 @@ static ICE_noinline int unmap_and_move(new_page_t get_new_page,
> */
> if (likely(!__PageMovable(page)))
> mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON +
> - page_is_file_cache(page), -hpage_nr_pages(page));
> + page_is_file_lru(page), -hpage_nr_pages(page));
> }
>
> /*
> @@ -1595,7 +1595,7 @@ static int add_page_for_migration(struct mm_struct *mm, unsigned long addr,
> err = 1;
> list_add_tail(&head->lru, pagelist);
> mod_node_page_state(page_pgdat(head),
> - NR_ISOLATED_ANON + page_is_file_cache(head),
> + NR_ISOLATED_ANON + page_is_file_lru(head),
> hpage_nr_pages(head));
> }
> out_putpage:
> @@ -1958,7 +1958,7 @@ static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
> return 0;
> }
>
> - page_lru = page_is_file_cache(page);
> + page_lru = page_is_file_lru(page);
> mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON + page_lru,
> hpage_nr_pages(page));
>
> @@ -1994,7 +1994,7 @@ int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma,
> * Don't migrate file pages that are mapped in multiple processes
> * with execute permissions as they are probably shared libraries.
> */
> - if (page_mapcount(page) != 1 && page_is_file_cache(page) &&
> + if (page_mapcount(page) != 1 && page_is_file_lru(page) &&
> (vma->vm_flags & VM_EXEC))
> goto out;
>
> @@ -2002,7 +2002,7 @@ int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma,
> * Also do not migrate dirty pages as not all filesystems can move
> * dirty pages in MIGRATE_ASYNC mode which is a waste of cycles.
> */
> - if (page_is_file_cache(page) && PageDirty(page))
> + if (page_is_file_lru(page) && PageDirty(page))
> goto out;
>
> isolated = numamigrate_isolate_page(pgdat, page);
> @@ -2017,7 +2017,7 @@ int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma,
> if (!list_empty(&migratepages)) {
> list_del(&page->lru);
> dec_node_page_state(page, NR_ISOLATED_ANON +
> - page_is_file_cache(page));
> + page_is_file_lru(page));
> putback_lru_page(page);
> }
> isolated = 0;
> @@ -2047,7 +2047,7 @@ int migrate_misplaced_transhuge_page(struct mm_struct *mm,
> pg_data_t *pgdat = NODE_DATA(node);
> int isolated = 0;
> struct page *new_page = NULL;
> - int page_lru = page_is_file_cache(page);
> + int page_lru = page_is_file_lru(page);
> unsigned long start = address & HPAGE_PMD_MASK;
>
> new_page = alloc_pages_node(node,
> diff --git a/mm/mprotect.c b/mm/mprotect.c
> index 4d30c4b549e1..494192ca954b 100644
> --- a/mm/mprotect.c
> +++ b/mm/mprotect.c
> @@ -102,7 +102,7 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
> * it cannot move them all from MIGRATE_ASYNC
> * context.
> */
> - if (page_is_file_cache(page) && PageDirty(page))
> + if (page_is_file_lru(page) && PageDirty(page))
> continue;
>
> /*
> diff --git a/mm/swap.c b/mm/swap.c
> index 6a8be910b14d..f70e8b0b7319 100644
> --- a/mm/swap.c
> +++ b/mm/swap.c
> @@ -276,7 +276,7 @@ static void __activate_page(struct page *page, struct lruvec *lruvec,
> void *arg)
> {
> if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
> - int file = page_is_file_cache(page);
> + int file = page_is_file_lru(page);
> int lru = page_lru_base_type(page);
>
> del_page_from_lru_list(page, lruvec, lru);
> @@ -394,7 +394,7 @@ void mark_page_accessed(struct page *page)
> else
> __lru_cache_activate_page(page);
> ClearPageReferenced(page);
> - if (page_is_file_cache(page))
> + if (page_is_file_lru(page))
> workingset_activation(page);
> }
> if (page_is_idle(page))
> @@ -515,7 +515,7 @@ static void lru_deactivate_file_fn(struct page *page, struct lruvec *lruvec,
> return;
>
> active = PageActive(page);
> - file = page_is_file_cache(page);
> + file = page_is_file_lru(page);
> lru = page_lru_base_type(page);
>
> del_page_from_lru_list(page, lruvec, lru + active);
> @@ -548,7 +548,7 @@ static void lru_deactivate_fn(struct page *page, struct lruvec *lruvec,
> void *arg)
> {
> if (PageLRU(page) && PageActive(page) && !PageUnevictable(page)) {
> - int file = page_is_file_cache(page);
> + int file = page_is_file_lru(page);
> int lru = page_lru_base_type(page);
>
> del_page_from_lru_list(page, lruvec, lru + LRU_ACTIVE);
> @@ -573,9 +573,9 @@ static void lru_lazyfree_fn(struct page *page, struct lruvec *lruvec,
> ClearPageActive(page);
> ClearPageReferenced(page);
> /*
> - * lazyfree pages are clean anonymous pages. They have
> - * SwapBacked flag cleared to distinguish normal anonymous
> - * pages
> + * Lazyfree pages are clean anonymous pages. They have
> + * PG_swapbacked flag cleared, to distinguish them from normal
> + * anonymous pages
> */
> ClearPageSwapBacked(page);
> add_page_to_lru_list(page, lruvec, LRU_INACTIVE_FILE);
> @@ -963,7 +963,7 @@ static void __pagevec_lru_add_fn(struct page *page, struct lruvec *lruvec,
>
> if (page_evictable(page)) {
> lru = page_lru(page);
> - update_page_reclaim_stat(lruvec, page_is_file_cache(page),
> + update_page_reclaim_stat(lruvec, page_is_file_lru(page),
> PageActive(page));
> if (was_unevictable)
> count_vm_event(UNEVICTABLE_PGRESCUED);
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index d9fb680884b8..d290a268dd68 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -919,7 +919,7 @@ static int __remove_mapping(struct address_space *mapping, struct page *page,
> * exceptional entries and shadow exceptional entries in the
> * same address_space.
> */
> - if (reclaimed && page_is_file_cache(page) &&
> + if (reclaimed && page_is_file_lru(page) &&
> !mapping_exiting(mapping) && !dax_mapping(mapping))
> shadow = workingset_eviction(page, target_memcg);
> __delete_from_page_cache(page, shadow);
> @@ -1043,7 +1043,7 @@ static void page_check_dirty_writeback(struct page *page,
> * Anonymous pages are not handled by flushers and must be written
> * from reclaim context. Do not stall reclaim based on them
> */
> - if (!page_is_file_cache(page) ||
> + if (!page_is_file_lru(page) ||
> (PageAnon(page) && !PageSwapBacked(page))) {
> *dirty = false;
> *writeback = false;
> @@ -1316,7 +1316,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
> * the rest of the LRU for clean pages and see
> * the same dirty pages again (PageReclaim).
> */
> - if (page_is_file_cache(page) &&
> + if (page_is_file_lru(page) &&
> (!current_is_kswapd() || !PageReclaim(page) ||
> !test_bit(PGDAT_DIRTY, &pgdat->flags))) {
> /*
> @@ -1460,7 +1460,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
> try_to_free_swap(page);
> VM_BUG_ON_PAGE(PageActive(page), page);
> if (!PageMlocked(page)) {
> - int type = page_is_file_cache(page);
> + int type = page_is_file_lru(page);
> SetPageActive(page);
> stat->nr_activate[type] += nr_pages;
> count_memcg_page_event(page, PGACTIVATE);
> @@ -1498,7 +1498,7 @@ unsigned long reclaim_clean_pages_from_list(struct zone *zone,
> LIST_HEAD(clean_pages);
>
> list_for_each_entry_safe(page, next, page_list, lru) {
> - if (page_is_file_cache(page) && !PageDirty(page) &&
> + if (page_is_file_lru(page) && !PageDirty(page) &&
> !__PageMovable(page) && !PageUnevictable(page)) {
> ClearPageActive(page);
> list_move(&page->lru, &clean_pages);
> @@ -2054,7 +2054,7 @@ static void shrink_active_list(unsigned long nr_to_scan,
> * IO, plus JVM can create lots of anon VM_EXEC pages,
> * so we ignore them here.
> */
> - if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
> + if ((vm_flags & VM_EXEC) && page_is_file_lru(page)) {
> list_add(&page->lru, &l_active);
> continue;
> }
> --
> 2.25.0

Nice cleanup. With Michal's updated comment.

Acked-by: Pankaj Gupta <pankaj.gupta.linux@xxxxxxxxx>

>
>

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