On Fri, 17 Feb 2017, Huang, Ying wrote: > > I found a memory leak in __read_swap_cache_async() introduced by mm-swap > series, and confirmed it via testing. Could you verify whether it fixed > your cases? Thanks a lot for reporting.
Well caught! That indeed fixes the leak I've been seeing: my load has now passed the 7 hour danger mark, with no indication of slowing down. I'll keep it running until I need to try something else on that machine, but all good for now. You could add Tested-by: Hugh Dickins <[email protected]> but don't bother: I'm sure Andrew will simply fold this fix into the fixed patch later on. Thanks, Hugh > > Best Regards, > Huang, Ying > > -------------------------------------------------------------------------> > From 4b96423796ab7435104eb2cb4dcf5d525b9e0800 Mon Sep 17 00:00:00 2001 > From: Huang Ying <[email protected]> > Date: Fri, 17 Feb 2017 10:31:37 +0800 > Subject: [PATCH] mm, swap: Fix memory leak in __read_swap_cache_async() > > The memory may be leaked in __read_swap_cache_async(). For the cases > as below, > > CPU 0 CPU 1 > ----- ----- > > find_get_page() == NULL > __swp_swapcount() != 0 > new_page = alloc_page_vma() > radix_tree_maybe_preload() > swap in swap slot > swapcache_prepare() == -EEXIST > cond_resched() > reclaim the swap slot > find_get_page() == NULL > __swp_swapcount() == 0 > return NULL <- new_page leaked here !!! > > The memory leak has been confirmed via checking the value of new_page > when returning inside the loop in __read_swap_cache_async(). > > This is fixed via replacing return with break inside of loop in > __read_swap_cache_async(), so that there is opportunity for the > new_page to be checked and freed. > > Reported-by: Hugh Dickins <[email protected]> > Cc: Tim Chen <[email protected]> > Signed-off-by: "Huang, Ying" <[email protected]> > --- > mm/swap_state.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/swap_state.c b/mm/swap_state.c > index 2126e9ba23b2..473b71e052a8 100644 > --- a/mm/swap_state.c > +++ b/mm/swap_state.c > @@ -333,7 +333,7 @@ struct page *__read_swap_cache_async(swp_entry_t entry, > gfp_t gfp_mask, > * else swap_off will be aborted if we return NULL. > */ > if (!__swp_swapcount(entry) && swap_slot_cache_enabled) > - return NULL; > + break; > > /* > * Get a new page to read into from swap. > -- > 2.11.0 > >
