From: Zqiang Date: Wed, 12 Apr 2023 14:31:27 +0000 (+0800) Subject: rcu/kvfree: Make fill page cache start from krcp->nr_bkv_objs X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=60888b77a06ea16665e4df980bb86b418253e268;p=linux.git rcu/kvfree: Make fill page cache start from krcp->nr_bkv_objs When the fill_page_cache_func() function is invoked, it assumes that the cache of pages is completely empty. However, there can be some time between triggering execution of this function and its actual invocation. During this time, kfree_rcu_work() might run, and might fill in part or all of this cache of pages, thus invalidating the fill_page_cache_func() function's assumption. This will not overfill the cache because put_cached_bnode() will reject the extra page. However, it will result in a needless allocation and freeing of one extra page, which might not be helpful under lowish-memory conditions. This commit therefore causes the fill_page_cache_func() to explicitly account for pages that have been placed into the cache shortly before it starts running. Signed-off-by: Zqiang Reviewed-by: Uladzislau Rezki (Sony) Signed-off-by: Paul E. McKenney --- diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 18f592bf6dc61..98f2e833e217e 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -3201,7 +3201,7 @@ static void fill_page_cache_func(struct work_struct *work) nr_pages = atomic_read(&krcp->backoff_page_cache_fill) ? 1 : rcu_min_cached_objs; - for (i = 0; i < nr_pages; i++) { + for (i = READ_ONCE(krcp->nr_bkv_objs); i < nr_pages; i++) { bnode = (struct kvfree_rcu_bulk_data *) __get_free_page(GFP_KERNEL | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);