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zsmalloc: account the number of compacted pages correctly
commit2395928158
upstream. There exists multiple path may do zram compaction concurrently. 1. auto-compaction triggered during memory reclaim 2. userspace utils write zram<id>/compaction node So, multiple threads may call zs_shrinker_scan/zs_compact concurrently. But pages_compacted is a per zsmalloc pool variable and modification of the variable is not serialized(through under class->lock). There are two issues here: 1. the pages_compacted may not equal to total number of pages freed(due to concurrently add). 2. zs_shrinker_scan may not return the correct number of pages freed(issued by current shrinker). The fix is simple: 1. account the number of pages freed in zs_compact locally. 2. use actomic variable pages_compacted to accumulate total number. Link: https://lkml.kernel.org/r/20210202122235.26885-1-wu-yan@tcl.com Fixes:860c707dca
("zsmalloc: account the number of compacted pages") Signed-off-by: Rokudo Yan <wu-yan@tcl.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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9c62adb6e2
commit
02f768edb9
3 changed files with 13 additions and 8 deletions
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@ -1078,7 +1078,7 @@ static ssize_t mm_stat_show(struct device *dev,
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zram->limit_pages << PAGE_SHIFT,
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max_used << PAGE_SHIFT,
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(u64)atomic64_read(&zram->stats.same_pages),
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pool_stats.pages_compacted,
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atomic_long_read(&pool_stats.pages_compacted),
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(u64)atomic64_read(&zram->stats.huge_pages));
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up_read(&zram->init_lock);
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@ -35,7 +35,7 @@ enum zs_mapmode {
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struct zs_pool_stats {
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/* How many pages were migrated (freed) */
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unsigned long pages_compacted;
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atomic_long_t pages_compacted;
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};
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struct zs_pool;
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@ -2216,11 +2216,13 @@ static unsigned long zs_can_compact(struct size_class *class)
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return obj_wasted * class->pages_per_zspage;
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}
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static void __zs_compact(struct zs_pool *pool, struct size_class *class)
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static unsigned long __zs_compact(struct zs_pool *pool,
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struct size_class *class)
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{
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struct zs_compact_control cc;
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struct zspage *src_zspage;
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struct zspage *dst_zspage = NULL;
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unsigned long pages_freed = 0;
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spin_lock(&class->lock);
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while ((src_zspage = isolate_zspage(class, true))) {
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@ -2250,7 +2252,7 @@ static void __zs_compact(struct zs_pool *pool, struct size_class *class)
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putback_zspage(class, dst_zspage);
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if (putback_zspage(class, src_zspage) == ZS_EMPTY) {
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free_zspage(pool, class, src_zspage);
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pool->stats.pages_compacted += class->pages_per_zspage;
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pages_freed += class->pages_per_zspage;
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}
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spin_unlock(&class->lock);
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cond_resched();
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@ -2261,12 +2263,15 @@ static void __zs_compact(struct zs_pool *pool, struct size_class *class)
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putback_zspage(class, src_zspage);
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spin_unlock(&class->lock);
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return pages_freed;
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}
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unsigned long zs_compact(struct zs_pool *pool)
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{
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int i;
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struct size_class *class;
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unsigned long pages_freed = 0;
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for (i = ZS_SIZE_CLASSES - 1; i >= 0; i--) {
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class = pool->size_class[i];
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@ -2274,10 +2279,11 @@ unsigned long zs_compact(struct zs_pool *pool)
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continue;
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if (class->index != i)
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continue;
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__zs_compact(pool, class);
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pages_freed += __zs_compact(pool, class);
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}
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atomic_long_add(pages_freed, &pool->stats.pages_compacted);
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return pool->stats.pages_compacted;
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return pages_freed;
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}
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EXPORT_SYMBOL_GPL(zs_compact);
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@ -2294,13 +2300,12 @@ static unsigned long zs_shrinker_scan(struct shrinker *shrinker,
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struct zs_pool *pool = container_of(shrinker, struct zs_pool,
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shrinker);
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pages_freed = pool->stats.pages_compacted;
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/*
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* Compact classes and calculate compaction delta.
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* Can run concurrently with a manually triggered
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* (by user) compaction.
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*/
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pages_freed = zs_compact(pool) - pages_freed;
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pages_freed = zs_compact(pool);
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return pages_freed ? pages_freed : SHRINK_STOP;
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}
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