• Weijie Yang's avatar
    mm/zswap: bugfix: memory leak when re-swapon · aa9bca05
    Weijie Yang authored
    zswap_tree is not freed when swapoff, and it got re-kmalloced in swapon,
    so a memory leak occurs.
    
    Free the memory of zswap_tree in zswap_frontswap_invalidate_area().
    Signed-off-by: default avatarWeijie Yang <weijie.yang@samsung.com>
    Reviewed-by: default avatarBob Liu <bob.liu@oracle.com>
    Cc: Minchan Kim <minchan@kernel.org>
    Reviewed-by: default avatarMinchan Kim <minchan@kernel.org>
    Cc: <stable@vger.kernel.org>
    From: Weijie Yang <weijie.yang@samsung.com>
    Subject: 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.
    
    [akpm@linux-foundation.org: coding-style fixes]
    Signed-off-by: default avatarWeijie Yang <weijie.yang@samsung.com>
    Reviewed-by: default avatarBob Liu <bob.liu@oracle.com>
    Cc: Minchan Kim <minchan@kernel.org>
    Cc: <stable@vger.kernel.org>
    Acked-by: default avatarSeth Jennings <sjenning@linux.vnet.ibm.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    aa9bca05
zswap.c 23.9 KB