[PATCH 5.10 005/106] mm/vmscan: __isolate_lru_page_prepare() cleanup

Greg Kroah-Hartman
2022-12-12T13:13:33Z

From: Alex Shi <alex.shi@linux.alibaba.com>

[ Upstream commit c2135f7c570bc274035834848d9bf46ea89ba763 ]

The function just returns 2 results, so using a 'switch' to deal with its
result is unnecessary. Also simplify it to a bool func as Vlastimil
suggested.

Also remove 'goto' by reusing list_move(), and take Matthew Wilcox's
suggestion to update comments in function.

Link: https://lkml.kernel.org/r/728874d7-2d93-4049-68c1-dcc3b2d52ccd@linux.alibaba.com
Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Stable-dep-of: 829ae0f81ce0 ("mm: migrate: fix THP's mapcount on isolation")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
include/linux/swap.h | 2 +-
mm/compaction.c | 2 +-
mm/vmscan.c | 68 ++++++++++++++++++++------------------------
3 files changed, 33 insertions(+), 39 deletions(-)

diff --git a/include/linux/swap.h b/include/linux/swap.h
index 3577d3a6ec37..394d5de5d4b4 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -358,7 +358,7 @@ extern void lru_cache_add_inactive_or_unevictable(struct page *page,
extern unsigned long zone_reclaimable_pages(struct zone *zone);
extern unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
gfp_t gfp_mask, nodemask_t *mask);
-extern int __isolate_lru_page_prepare(struct page *page, isolate_mode_t mode);
+extern bool __isolate_lru_page_prepare(struct page *page, isolate_mode_t mode);
extern unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
unsigned long nr_pages,
gfp_t gfp_mask,
diff --git a/mm/compaction.c b/mm/compaction.c
index ba3e907f03b7..ea46aadc7c21 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -980,7 +980,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
if (unlikely(!get_page_unless_zero(page)))
goto isolate_fail;

- if (__isolate_lru_page_prepare(page, isolate_mode) != 0)
+ if (!__isolate_lru_page_prepare(page, isolate_mode))
goto isolate_fail_put;

/* Try isolate the page */
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 5ada402c8d95..00a47845a15b 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1543,19 +1543,17 @@ unsigned int reclaim_clean_pages_from_list(struct zone *zone,
* page: page to consider
* mode: one of the LRU isolation modes defined above
*
- * returns 0 on success, -ve errno on failure.
+ * returns true on success, false on failure.
*/
-int __isolate_lru_page_prepare(struct page *page, isolate_mode_t mode)
+bool __isolate_lru_page_prepare(struct page *page, isolate_mode_t mode)
{
- int ret = -EBUSY;
-
/* Only take pages on the LRU. */
if (!PageLRU(page))
- return ret;
+ return false;

/* Compaction should not handle unevictable pages but CMA can do so */
if (PageUnevictable(page) && !(mode & ISOLATE_UNEVICTABLE))
- return ret;
+ return false;

/*
* To minimise LRU disruption, the caller can indicate that it only
@@ -1568,7 +1566,7 @@ int __isolate_lru_page_prepare(struct page *page, isolate_mode_t mode)
if (mode & ISOLATE_ASYNC_MIGRATE) {
/* All the caller can do on PageWriteback is block */
if (PageWriteback(page))
- return ret;
+ return false;

if (PageDirty(page)) {
struct address_space *mapping;
@@ -1584,20 +1582,20 @@ int __isolate_lru_page_prepare(struct page *page, isolate_mode_t mode)
* from the page cache.
*/
if (!trylock_page(page))
- return ret;
+ return false;

mapping = page_mapping(page);
migrate_dirty = !mapping || mapping->a_ops->migratepage;
unlock_page(page);
if (!migrate_dirty)
- return ret;
+ return false;
}
}

if ((mode & ISOLATE_UNMAPPED) && page_mapped(page))
- return ret;
+ return false;

- return 0;
+ return true;
}

/*
@@ -1679,35 +1677,31 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
* only when the page is being freed somewhere else.
*/
scan += nr_pages;
- switch (__isolate_lru_page_prepare(page, mode)) {
- case 0:
- /*
- * Be careful not to clear PageLRU until after we're
- * sure the page is not being freed elsewhere -- the
- * page release code relies on it.
- */
- if (unlikely(!get_page_unless_zero(page)))
- goto busy;
-
- if (!TestClearPageLRU(page)) {
- /*
- * This page may in other isolation path,
- * but we still hold lru_lock.
- */
- put_page(page);
- goto busy;
- }
-
- nr_taken += nr_pages;
- nr_zone_taken[page_zonenum(page)] += nr_pages;
- list_move(&page->lru, dst);
- break;
+ if (!__isolate_lru_page_prepare(page, mode)) {
+ /* It is being freed elsewhere */
+ list_move(&page->lru, src);
+ continue;
+ }
+ /*
+ * Be careful not to clear PageLRU until after we're
+ * sure the page is not being freed elsewhere -- the
+ * page release code relies on it.
+ */
+ if (unlikely(!get_page_unless_zero(page))) {
+ list_move(&page->lru, src);
+ continue;
+ }

- default:
-busy:
- /* else it is being freed elsewhere */
+ if (!TestClearPageLRU(page)) {
+ /* Another thread is already isolating this page */
+ put_page(page);
list_move(&page->lru, src);
+ continue;
}
+
+ nr_taken += nr_pages;
+ nr_zone_taken[page_zonenum(page)] += nr_pages;
+ list_move(&page->lru, dst);
}

/*
--
2.35.1