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Subject[PATCH] mm: Code cleanup for MADV_FREE
Date
From: Huang Ying <ying.huang@intel.com>

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@intel.com>
Suggested-by: David Hildenbrand <david@redhat.com>
Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
Suggested-by: David Rientjes <rientjes@google.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@surriel.com>
---
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
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