From 7e924aafa4b03ff71de34af8553d9a1ebc86c071 Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Tue, 4 Mar 2008 14:29:08 -0800 Subject: [PATCH] memcg: mem_cgroup_charge never NULL My memcgroup patch to fix hang with shmem/tmpfs added NULL page handling to mem_cgroup_charge_common. It seemed convenient at the time, but hard to justify now: there's a perfectly appropriate swappage to charge and uncharge instead, this is not on any hot path through shmem_getpage, and no performance hit was observed from the slight extra overhead. So revert that NULL page handling from mem_cgroup_charge_common; and make it clearer by bringing page_cgroup_assign_new_page_cgroup into its body - that was a helper I found more of a hindrance to understanding. Signed-off-by: Hugh Dickins Cc: David Rientjes Acked-by: Balbir Singh Acked-by: KAMEZAWA Hiroyuki Cc: Hirokazu Takahashi Cc: YAMAMOTO Takashi Cc: Paul Menage Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/memcontrol.c | 61 +++++++++++++++++-------------------------------- mm/shmem.c | 9 +++++--- 2 files changed, 27 insertions(+), 43 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 9e170d3c71..83ba13ad31 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -300,25 +300,6 @@ static void __always_inline unlock_page_cgroup(struct page *page) bit_spin_unlock(PAGE_CGROUP_LOCK_BIT, &page->page_cgroup); } -/* - * Tie new page_cgroup to struct page under lock_page_cgroup() - * This can fail if the page has been tied to a page_cgroup. - * If success, returns 0. - */ -static int page_cgroup_assign_new_page_cgroup(struct page *page, - struct page_cgroup *pc) -{ - int ret = 0; - - lock_page_cgroup(page); - if (!page_get_page_cgroup(page)) - page_assign_page_cgroup(page, pc); - else /* A page is tied to other pc. */ - ret = 1; - unlock_page_cgroup(page); - return ret; -} - /* * Clear page->page_cgroup member under lock_page_cgroup(). * If given "pc" value is different from one page->page_cgroup, @@ -585,26 +566,24 @@ static int mem_cgroup_charge_common(struct page *page, struct mm_struct *mm, * with it */ retry: - if (page) { - lock_page_cgroup(page); - pc = page_get_page_cgroup(page); - /* - * The page_cgroup exists and - * the page has already been accounted. - */ - if (pc) { - if (unlikely(!atomic_inc_not_zero(&pc->ref_cnt))) { - /* this page is under being uncharged ? */ - unlock_page_cgroup(page); - cpu_relax(); - goto retry; - } else { - unlock_page_cgroup(page); - goto done; - } + lock_page_cgroup(page); + pc = page_get_page_cgroup(page); + /* + * The page_cgroup exists and + * the page has already been accounted. + */ + if (pc) { + if (unlikely(!atomic_inc_not_zero(&pc->ref_cnt))) { + /* this page is under being uncharged ? */ + unlock_page_cgroup(page); + cpu_relax(); + goto retry; + } else { + unlock_page_cgroup(page); + goto done; } - unlock_page_cgroup(page); } + unlock_page_cgroup(page); pc = kzalloc(sizeof(struct page_cgroup), gfp_mask); if (pc == NULL) @@ -663,7 +642,9 @@ retry: if (ctype == MEM_CGROUP_CHARGE_TYPE_CACHE) pc->flags |= PAGE_CGROUP_FLAG_CACHE; - if (!page || page_cgroup_assign_new_page_cgroup(page, pc)) { + lock_page_cgroup(page); + if (page_get_page_cgroup(page)) { + unlock_page_cgroup(page); /* * Another charge has been added to this page already. * We take lock_page_cgroup(page) again and read @@ -672,10 +653,10 @@ retry: res_counter_uncharge(&mem->res, PAGE_SIZE); css_put(&mem->css); kfree(pc); - if (!page) - goto done; goto retry; } + page_assign_page_cgroup(page, pc); + unlock_page_cgroup(page); mz = page_cgroup_zoneinfo(pc); spin_lock_irqsave(&mz->lru_lock, flags); diff --git a/mm/shmem.c b/mm/shmem.c index 90b576cbc0..3372bc579e 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -1370,14 +1370,17 @@ repeat: shmem_swp_unmap(entry); spin_unlock(&info->lock); unlock_page(swappage); - page_cache_release(swappage); if (error == -ENOMEM) { /* allow reclaim from this memory cgroup */ - error = mem_cgroup_cache_charge(NULL, + error = mem_cgroup_cache_charge(swappage, current->mm, gfp & ~__GFP_HIGHMEM); - if (error) + if (error) { + page_cache_release(swappage); goto failed; + } + mem_cgroup_uncharge_page(swappage); } + page_cache_release(swappage); goto repeat; } } else if (sgp == SGP_READ && !filepage) { -- 2.39.5