[PATCH 5.10 004/106] mm/compaction: do page isolation first in compaction

Greg Kroah-Hartman
2022-12-12T13:12:49Z

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

[ Upstream commit 9df41314390b81a541ca6e84c8340bad0959e4b5 ]

Currently, compaction would get the lru_lock and then do page isolation
which works fine with pgdat->lru_lock, since any page isoltion would
compete for the lru_lock. If we want to change to memcg lru_lock, we have
to isolate the page before getting lru_lock, thus isoltion would block
page's memcg change which relay on page isoltion too. Then we could
safely use per memcg lru_lock later.

The new page isolation use previous introduced TestClearPageLRU() + pgdat
lru locking which will be changed to memcg lru lock later.

Hugh Dickins <hughd@google.com> fixed following bugs in this patch's early
version:

Fix lots of crashes under compaction load: isolate_migratepages_block()
must clean up appropriately when rejecting a page, setting PageLRU again
if it had been cleared; and a put_page() after get_page_unless_zero()
cannot safely be done while holding locked_lruvec - it may turn out to be
the final put_page(), which will take an lruvec lock when PageLRU.

And move __isolate_lru_page_prepare back after get_page_unless_zero to
make trylock_page() safe: trylock_page() is not safe to use at this time:
its setting PG_locked can race with the page being freed or allocated
("Bad page"), and can also erase flags being set by one of those "sole
owners" of a freshly allocated page who use non-atomic __SetPageFlag().

Link: https://lkml.kernel.org/r/1604566549-62481-16-git-send-email-alex.shi@linux.alibaba.com
Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Acked-by: Hugh Dickins <hughd@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Alexander Duyck <alexander.duyck@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: "Chen, Rong A" <rong.a.chen@intel.com>
Cc: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Jann Horn <jannh@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mika Penttilä <mika.penttila@nextfour.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Yang Shi <yang.shi@linux.alibaba.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 | 42 +++++++++++++++++++++++++++++++++---------
mm/vmscan.c | 43 ++++++++++++++++++++++---------------------
3 files changed, 56 insertions(+), 31 deletions(-)

diff --git a/include/linux/swap.h b/include/linux/swap.h
index fbc6805358da..3577d3a6ec37 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(struct page *page, isolate_mode_t mode);
+extern int __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 8dfbe86bd74f..ba3e907f03b7 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -890,6 +890,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
if (!valid_page && IS_ALIGNED(low_pfn, pageblock_nr_pages)) {
if (!cc->ignore_skip_hint && get_pageblock_skip(page)) {
low_pfn = end_pfn;
+ page = NULL;
goto isolate_abort;
}
valid_page = page;
@@ -971,6 +972,21 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
if (!(cc->gfp_mask & __GFP_FS) && page_mapping(page))
goto isolate_fail;

+ /*
+ * 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 isolate_fail;
+
+ if (__isolate_lru_page_prepare(page, isolate_mode) != 0)
+ goto isolate_fail_put;
+
+ /* Try isolate the page */
+ if (!TestClearPageLRU(page))
+ goto isolate_fail_put;
+
/* If we already hold the lock, we can skip some rechecking */
if (!locked) {
locked = compact_lock_irqsave(&pgdat->lru_lock,
@@ -983,10 +999,6 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
goto isolate_abort;
}

- /* Recheck PageLRU and PageCompound under lock */
- if (!PageLRU(page))
- goto isolate_fail;
-
/*
* Page become compound since the non-locked check,
* and it's on LRU. It can only be a THP so the order
@@ -994,16 +1006,13 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
*/
if (unlikely(PageCompound(page) && !cc->alloc_contig)) {
low_pfn += compound_nr(page) - 1;
- goto isolate_fail;
+ SetPageLRU(page);
+ goto isolate_fail_put;
}
}

lruvec = mem_cgroup_page_lruvec(page, pgdat);

- /* Try isolate the page */
- if (__isolate_lru_page(page, isolate_mode) != 0)
- goto isolate_fail;
-
/* The whole page is taken off the LRU; skip the tail pages. */
if (PageCompound(page))
low_pfn += compound_nr(page) - 1;
@@ -1032,6 +1041,15 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
}

continue;
+
+isolate_fail_put:
+ /* Avoid potential deadlock in freeing page under lru_lock */
+ if (locked) {
+ spin_unlock_irqrestore(&pgdat->lru_lock, flags);
+ locked = false;
+ }
+ put_page(page);
+
isolate_fail:
if (!skip_on_failure)
continue;
@@ -1068,9 +1086,15 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
if (unlikely(low_pfn > end_pfn))
low_pfn = end_pfn;

+ page = NULL;
+
isolate_abort:
if (locked)
spin_unlock_irqrestore(&pgdat->lru_lock, flags);
+ if (page) {
+ SetPageLRU(page);
+ put_page(page);
+ }

/*
* Updated the cached scanner pfn once the pageblock has been scanned
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 8d62eedfc794..5ada402c8d95 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1545,7 +1545,7 @@ unsigned int reclaim_clean_pages_from_list(struct zone *zone,
*
* returns 0 on success, -ve errno on failure.
*/
-int __isolate_lru_page(struct page *page, isolate_mode_t mode)
+int __isolate_lru_page_prepare(struct page *page, isolate_mode_t mode)
{
int ret = -EBUSY;

@@ -1597,22 +1597,9 @@ int __isolate_lru_page(struct page *page, isolate_mode_t mode)
if ((mode & ISOLATE_UNMAPPED) && page_mapped(page))
return ret;

- if (likely(get_page_unless_zero(page))) {
- /*
- * 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 (TestClearPageLRU(page))
- ret = 0;
- else
- put_page(page);
- }
-
- return ret;
+ return 0;
}

-
/*
* Update LRU sizes after isolating pages. The LRU size updates must
* be complete before mem_cgroup_update_lru_size due to a sanity check.
@@ -1692,20 +1679,34 @@ 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(page, mode)) {
+ 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;

- case -EBUSY:
+ default:
+busy:
/* else it is being freed elsewhere */
list_move(&page->lru, src);
- continue;
-
- default:
- BUG();
}
}

--
2.35.1