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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>
59 lines
1.6 KiB
C
59 lines
1.6 KiB
C
/*
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* zsmalloc memory allocator
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*
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* Copyright (C) 2011 Nitin Gupta
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* Copyright (C) 2012, 2013 Minchan Kim
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*
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* This code is released using a dual license strategy: BSD/GPL
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* You can choose the license that better fits your requirements.
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*
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* Released under the terms of 3-clause BSD License
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* Released under the terms of GNU General Public License Version 2.0
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*/
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#ifndef _ZS_MALLOC_H_
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#define _ZS_MALLOC_H_
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#include <linux/types.h>
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/*
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* zsmalloc mapping modes
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*
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* NOTE: These only make a difference when a mapped object spans pages.
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*/
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enum zs_mapmode {
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ZS_MM_RW, /* normal read-write mapping */
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ZS_MM_RO, /* read-only (no copy-out at unmap time) */
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ZS_MM_WO /* write-only (no copy-in at map time) */
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/*
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* NOTE: ZS_MM_WO should only be used for initializing new
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* (uninitialized) allocations. Partial writes to already
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* initialized allocations should use ZS_MM_RW to preserve the
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* existing data.
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*/
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};
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struct zs_pool_stats {
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/* How many pages were migrated (freed) */
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atomic_long_t pages_compacted;
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};
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struct zs_pool;
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struct zs_pool *zs_create_pool(const char *name);
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void zs_destroy_pool(struct zs_pool *pool);
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unsigned long zs_malloc(struct zs_pool *pool, size_t size, gfp_t flags);
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void zs_free(struct zs_pool *pool, unsigned long obj);
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size_t zs_huge_class_size(struct zs_pool *pool);
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void *zs_map_object(struct zs_pool *pool, unsigned long handle,
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enum zs_mapmode mm);
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void zs_unmap_object(struct zs_pool *pool, unsigned long handle);
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unsigned long zs_get_total_pages(struct zs_pool *pool);
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unsigned long zs_compact(struct zs_pool *pool);
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void zs_pool_stats(struct zs_pool *pool, struct zs_pool_stats *stats);
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#endif
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