From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757000Ab1FIWjR (ORCPT ); Thu, 9 Jun 2011 18:39:17 -0400 Received: from smtp-out.google.com ([74.125.121.67]:46039 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752710Ab1FIWjN (ORCPT ); Thu, 9 Jun 2011 18:39:13 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=google.com; s=beta; h=date:from:x-x-sender:to:cc:subject:in-reply-to:message-id :references:user-agent:mime-version:content-type; b=psR3r7fWe1tvzd7GxOi6lXa7hjSvJllhDmPEQqzrmn1+h4sVRlFW09bY4A7JqeUpT/ 7xmfItTaGBCYogLe3xlw== Date: Thu, 9 Jun 2011 15:39:07 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@sister.anvils To: Andrew Morton cc: Shaohua Li , "Zhang, Yanmin" , Tim Chen , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH 5/7] tmpfs: simplify prealloc_page In-Reply-To: Message-ID: References: User-Agent: Alpine 2.00 (LSU 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The prealloc_page handling in shmem_getpage_gfp() is unnecessarily complicated: first simplify that before going on to filepage/swappage. That's right, don't report ENOMEM when the preallocation fails: we may or may not need the page. But simply report ENOMEM once we find we do need it, instead of dropping lock, repeating allocation, unwinding on failure etc. And leave the out label on the fast path, don't goto. Fix something that looks like a bug but turns out not to be: set PageSwapBacked on prealloc_page before its mem_cgroup_cache_charge(), as the removed case was doing. That's important before adding to LRU (determines which LRU the page goes on), and does affect which path it takes through memcontrol.c, but in the end MEM_CGROUP_CHANGE_TYPE_ SHMEM is handled no differently from CACHE. Signed-off-by: Hugh Dickins Cc: Shaohua Li Cc: "Zhang, Yanmin" Cc: Tim Chen --- mm/shmem.c | 59 ++++++++++++--------------------------------------- 1 file changed, 15 insertions(+), 44 deletions(-) --- linux.orig/mm/shmem.c 2011-06-09 11:39:32.361240481 -0700 +++ linux/mm/shmem.c 2011-06-09 11:39:42.845292474 -0700 @@ -1269,9 +1269,9 @@ repeat: goto failed; radix_tree_preload_end(); if (sgp != SGP_READ && !prealloc_page) { - /* We don't care if this fails */ prealloc_page = shmem_alloc_page(gfp, info, idx); if (prealloc_page) { + SetPageSwapBacked(prealloc_page); if (mem_cgroup_cache_charge(prealloc_page, current->mm, GFP_KERNEL)) { page_cache_release(prealloc_page); @@ -1403,7 +1403,8 @@ repeat: goto repeat; } spin_unlock(&info->lock); - } else { + + } else if (prealloc_page) { shmem_swp_unmap(entry); sbinfo = SHMEM_SB(inode->i_sb); if (sbinfo->max_blocks) { @@ -1419,41 +1420,8 @@ repeat: if (!filepage) { int ret; - if (!prealloc_page) { - spin_unlock(&info->lock); - filepage = shmem_alloc_page(gfp, info, idx); - if (!filepage) { - spin_lock(&info->lock); - shmem_unacct_blocks(info->flags, 1); - shmem_free_blocks(inode, 1); - spin_unlock(&info->lock); - error = -ENOMEM; - goto failed; - } - SetPageSwapBacked(filepage); - - /* - * Precharge page while we can wait, compensate - * after - */ - error = mem_cgroup_cache_charge(filepage, - current->mm, GFP_KERNEL); - if (error) { - page_cache_release(filepage); - spin_lock(&info->lock); - shmem_unacct_blocks(info->flags, 1); - shmem_free_blocks(inode, 1); - spin_unlock(&info->lock); - filepage = NULL; - goto failed; - } - - spin_lock(&info->lock); - } else { - filepage = prealloc_page; - prealloc_page = NULL; - SetPageSwapBacked(filepage); - } + filepage = prealloc_page; + prealloc_page = NULL; entry = shmem_swp_alloc(info, idx, sgp, gfp); if (IS_ERR(entry)) @@ -1492,11 +1460,19 @@ repeat: SetPageUptodate(filepage); if (sgp == SGP_DIRTY) set_page_dirty(filepage); + } else { + error = -ENOMEM; + goto out; } done: *pagep = filepage; error = 0; - goto out; +out: + if (prealloc_page) { + mem_cgroup_uncharge_cache_page(prealloc_page); + page_cache_release(prealloc_page); + } + return error; nospace: /* @@ -1520,12 +1496,7 @@ failed: unlock_page(filepage); page_cache_release(filepage); } -out: - if (prealloc_page) { - mem_cgroup_uncharge_cache_page(prealloc_page); - page_cache_release(prealloc_page); - } - return error; + goto out; } static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)