mm/zswap: bugfix: memory leak when invalidate and reclaim occur concurrently
Consider the following scenario: thread 0: reclaim entry x (get refcount, but not call zswap_get_swap_cache_page) thread 1: call zswap_frontswap_invalidate_page to invalidate entry x. finished, entry x and its zbud is not freed as its refcount != 0 now, the swap_map[x] = 0 thread 0: now call zswap_get_swap_cache_page swapcache_prepare return -ENOENT because entry x is not used any more zswap_get_swap_cache_page return ZSWAP_SWAPCACHE_NOMEM zswap_writeback_entry do nothing except put refcount Now, the memory of zswap_entry x and its zpage leak. Modify: - check the refcount in fail path, free memory if it is not referenced. - use ZSWAP_SWAPCACHE_FAIL instead of ZSWAP_SWAPCACHE_NOMEM as the fail path can be not only caused by nomem but also by invalidate. Signed-off-by: Weijie Yang <weijie.yang@samsung.com> Reviewed-by: Bob Liu <bob.liu@oracle.com> Reviewed-by: Minchan Kim <minchan@kernel.org> Acked-by: Seth Jennings <sjenning@linux.vnet.ibm.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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7a67d7abcc
Коммит
67d13fe846
22
mm/zswap.c
22
mm/zswap.c
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@ -387,7 +387,7 @@ static void zswap_free_entry(struct zswap_tree *tree, struct zswap_entry *entry)
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enum zswap_get_swap_ret {
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ZSWAP_SWAPCACHE_NEW,
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ZSWAP_SWAPCACHE_EXIST,
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ZSWAP_SWAPCACHE_NOMEM
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ZSWAP_SWAPCACHE_FAIL,
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};
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/*
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@ -401,9 +401,10 @@ enum zswap_get_swap_ret {
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* added to the swap cache, and returned in retpage.
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*
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* If success, the swap cache page is returned in retpage
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* Returns 0 if page was already in the swap cache, page is not locked
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* Returns 1 if the new page needs to be populated, page is locked
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* Returns <0 on error
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* Returns ZSWAP_SWAPCACHE_EXIST if page was already in the swap cache
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* Returns ZSWAP_SWAPCACHE_NEW if the new page needs to be populated,
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* the new page is added to swapcache and locked
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* Returns ZSWAP_SWAPCACHE_FAIL on error
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*/
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static int zswap_get_swap_cache_page(swp_entry_t entry,
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struct page **retpage)
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@ -475,7 +476,7 @@ static int zswap_get_swap_cache_page(swp_entry_t entry,
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if (new_page)
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page_cache_release(new_page);
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if (!found_page)
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return ZSWAP_SWAPCACHE_NOMEM;
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return ZSWAP_SWAPCACHE_FAIL;
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*retpage = found_page;
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return ZSWAP_SWAPCACHE_EXIST;
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}
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@ -529,11 +530,11 @@ static int zswap_writeback_entry(struct zbud_pool *pool, unsigned long handle)
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/* try to allocate swap cache page */
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switch (zswap_get_swap_cache_page(swpentry, &page)) {
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case ZSWAP_SWAPCACHE_NOMEM: /* no memory */
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case ZSWAP_SWAPCACHE_FAIL: /* no memory or invalidate happened */
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ret = -ENOMEM;
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goto fail;
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case ZSWAP_SWAPCACHE_EXIST: /* page is unlocked */
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case ZSWAP_SWAPCACHE_EXIST:
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/* page is already in the swap cache, ignore for now */
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page_cache_release(page);
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ret = -EEXIST;
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@ -594,7 +595,12 @@ static int zswap_writeback_entry(struct zbud_pool *pool, unsigned long handle)
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fail:
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spin_lock(&tree->lock);
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zswap_entry_put(entry);
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refcount = zswap_entry_put(entry);
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if (refcount <= 0) {
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/* invalidate happened, consider writeback as success */
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zswap_free_entry(tree, entry);
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ret = 0;
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}
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spin_unlock(&tree->lock);
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return ret;
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}
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