[patch 022/166] mm: code cleanup for MADV_FREE

Andrew Morton
2020-04-07T03:04:45Z

From: Huang Ying <ying.huang@intel.com>
Subject: mm: code cleanup for MADV_FREE

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.

Link: http://lkml.kernel.org/r/20200317100342.2730705-1-ying.huang@intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Suggested-by: David Hildenbrand <david@redhat.com>
Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Suggested-by: David Rientjes <rientjes@google.com>
Acked-by: David Rientjes <rientjes@google.com>
Acked-by: Michal Hocko <mhocko@kernel.org>
Acked-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

include/linux/mm_inline.h | 15 ++++++++-------
include/linux/page-flags.h | 5 +++++
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, 44 insertions(+), 38 deletions(-)

--- a/include/linux/mm_inline.h~mm-code-cleanup-for-madv_free
+++ a/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 a regular filesystem backed page cache page or a lazily
+ * freed anonymous page (e.g. via MADV_FREE). Returns 0 if @page is a normal
+ * anonymous page, a tmpfs page or otherwise ram or swap backed page. 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_fro
*/
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;
}
--- a/include/linux/page-flags.h~mm-code-cleanup-for-madv_free
+++ a/include/linux/page-flags.h
@@ -63,6 +63,11 @@
* page_waitqueue(page) is a wait queue of all tasks waiting for the page
* to become unlocked.
*
+ * PG_swapbacked is set when a page uses swap as a backing storage. This are
+ * usually PageAnon or shmem pages but please note that even anonymous pages
+ * might lose their PG_swapbacked flag when they simply can be dropped (e.g. as
+ * a result of MADV_FREE).
+ *
* 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.
*
--- a/include/trace/events/vmscan.h~mm-code-cleanup-for-madv_free
+++ a/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",
--- a/mm/compaction.c~mm-code-cleanup-for-madv_free
+++ a/mm/compaction.c
@@ -989,7 +989,7 @@ isolate_migratepages_block(struct compac
/* 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:
--- a/mm/gup.c~mm-code-cleanup-for-madv_free
+++ a/mm/gup.c
@@ -1677,7 +1677,7 @@ check_again:
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));
}
}
--- a/mm/khugepaged.c~mm-code-cleanup-for-madv_free
+++ a/mm/khugepaged.c
@@ -511,7 +511,7 @@ void __khugepaged_exit(struct mm_struct

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);
}
@@ -611,7 +611,7 @@ static int __collapse_huge_page_isolate(
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);

--- a/mm/memory-failure.c~mm-code-cleanup-for-madv_free
+++ a/mm/memory-failure.c
@@ -1810,7 +1810,7 @@ static int __soft_offline_page(struct pa
*/
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);
--- a/mm/memory_hotplug.c~mm-code-cleanup-for-madv_free
+++ a/mm/memory_hotplug.c
@@ -1317,7 +1317,7 @@ do_migrate_range(unsigned long start_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);
--- a/mm/mempolicy.c~mm-code-cleanup-for-madv_free
+++ a/mm/mempolicy.c
@@ -1022,7 +1022,7 @@ static int migrate_page_add(struct page
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) {
/*
--- a/mm/migrate.c~mm-code-cleanup-for-madv_free
+++ a/mm/migrate.c
@@ -193,7 +193,7 @@ void putback_movable_pages(struct list_h
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);
}
}
@@ -1219,7 +1219,7 @@ out:
*/
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));
}

/*
@@ -1592,7 +1592,7 @@ static int add_page_for_migration(struct
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:
@@ -1955,7 +1955,7 @@ static int numamigrate_isolate_page(pg_d
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));

@@ -1991,7 +1991,7 @@ int migrate_misplaced_page(struct page *
* 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;

@@ -1999,7 +1999,7 @@ int migrate_misplaced_page(struct page *
* 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);
@@ -2014,7 +2014,7 @@ int migrate_misplaced_page(struct page *
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;
@@ -2044,7 +2044,7 @@ int migrate_misplaced_transhuge_page(str
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,
--- a/mm/mprotect.c~mm-code-cleanup-for-madv_free
+++ a/mm/mprotect.c
@@ -98,7 +98,7 @@ static unsigned long change_pte_range(st
* 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;

/*
--- a/mm/swap.c~mm-code-cleanup-for-madv_free
+++ a/mm/swap.c
@@ -276,7 +276,7 @@ static void __activate_page(struct page
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 *pag
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(struc
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 pag
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
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);
@@ -962,7 +962,7 @@ static void __pagevec_lru_add_fn(struct

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);
--- a/mm/vmscan.c~mm-code-cleanup-for-madv_free
+++ a/mm/vmscan.c
@@ -919,7 +919,7 @@ static int __remove_mapping(struct addre
* 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(s
* 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;
@@ -1315,7 +1315,7 @@ static unsigned long shrink_page_list(st
* 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))) {
/*
@@ -1459,7 +1459,7 @@ activate_locked:
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);
@@ -1497,7 +1497,7 @@ unsigned long reclaim_clean_pages_from_l
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);
@@ -2053,7 +2053,7 @@ static void shrink_active_list(unsigned
* 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;
}
_