From 5c9bab592f53328b3e00d7293378b714abf47a2a Mon Sep 17 00:00:00 2001 From: Vitaly Wool Date: Thu, 5 Apr 2018 16:23:32 -0700 Subject: [PATCH] z3fold: limit use of stale list for allocation Currently if z3fold couldn't find an unbuddied page it would first try to pull a page off the stale list. The problem with this approach is that we can't 100% guarantee that the page is not processed by the workqueue thread at the same time unless we run cancel_work_sync() on it, which we can't do if we're in an atomic context. So let's just limit stale list usage to non-atomic contexts only. Link: http://lkml.kernel.org/r/47ab51e7-e9c1-d30e-ab17-f734dbc3abce@gmail.com Signed-off-by: Vitaly Vul Reviewed-by: Andrew Morton Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/z3fold.c | 35 +++++++++++++++++++---------------- 1 file changed, 19 insertions(+), 16 deletions(-) diff --git a/mm/z3fold.c b/mm/z3fold.c index d589d318727f..f579ad4a8100 100644 --- a/mm/z3fold.c +++ b/mm/z3fold.c @@ -620,24 +620,27 @@ lookup: bud = FIRST; } - spin_lock(&pool->stale_lock); - zhdr = list_first_entry_or_null(&pool->stale, - struct z3fold_header, buddy); - /* - * Before allocating a page, let's see if we can take one from the - * stale pages list. cancel_work_sync() can sleep so we must make - * sure it won't be called in case we're in atomic context. - */ - if (zhdr && (can_sleep || !work_pending(&zhdr->work))) { - list_del(&zhdr->buddy); - spin_unlock(&pool->stale_lock); - if (can_sleep) + page = NULL; + if (can_sleep) { + spin_lock(&pool->stale_lock); + zhdr = list_first_entry_or_null(&pool->stale, + struct z3fold_header, buddy); + /* + * Before allocating a page, let's see if we can take one from + * the stale pages list. cancel_work_sync() can sleep so we + * limit this case to the contexts where we can sleep + */ + if (zhdr) { + list_del(&zhdr->buddy); + spin_unlock(&pool->stale_lock); cancel_work_sync(&zhdr->work); - page = virt_to_page(zhdr); - } else { - spin_unlock(&pool->stale_lock); - page = alloc_page(gfp); + page = virt_to_page(zhdr); + } else { + spin_unlock(&pool->stale_lock); + } } + if (!page) + page = alloc_page(gfp); if (!page) return -ENOMEM;