From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg1-f199.google.com (mail-pg1-f199.google.com [209.85.215.199]) by kanga.kvack.org (Postfix) with ESMTP id B84F48E0001 for ; Wed, 19 Dec 2018 00:58:35 -0500 (EST) Received: by mail-pg1-f199.google.com with SMTP id r13so15757883pgb.7 for ; Tue, 18 Dec 2018 21:58:35 -0800 (PST) Received: from out4437.biz.mail.alibaba.com (out4437.biz.mail.alibaba.com. [47.88.44.37]) by mx.google.com with ESMTPS id a124si17031390pfb.263.2018.12.18.21.58.33 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 18 Dec 2018 21:58:34 -0800 (PST) Subject: Re: [RFC PATCH 1/2] mm: swap: check if swap backing device is congested or not References: <1545115948-25467-1-git-send-email-yang.shi@linux.alibaba.com> <6a51d47a-b87f-b0f1-4dae-843730dba698@linux.intel.com> <03462367-3f75-4907-8c5e-526a919e5cf3@linux.alibaba.com> From: Yang Shi Message-ID: <606b73ed-da62-fdd1-71da-c4de7a02e837@linux.alibaba.com> Date: Tue, 18 Dec 2018 21:56:49 -0800 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Sender: owner-linux-mm@kvack.org List-ID: To: Tim Chen , ying.huang@intel.com, tim.c.chen@intel.com, minchan@kernel.org, Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org On 12/18/18 4:16 PM, Tim Chen wrote: > On 12/18/18 3:43 PM, Yang Shi wrote: >> >> On 12/18/18 11:29 AM, Tim Chen wrote: >>> On 12/17/18 10:52 PM, Yang Shi wrote: >>> >>>> diff --git a/mm/swap_state.c b/mm/swap_state.c >>>> index fd2f21e..7cc3c29 100644 >>>> --- a/mm/swap_state.c >>>> +++ b/mm/swap_state.c >>>> @@ -538,11 +538,15 @@ struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask, >>>>       bool do_poll = true, page_allocated; >>>>       struct vm_area_struct *vma = vmf->vma; >>>>       unsigned long addr = vmf->address; >>>> +    struct inode *inode = si->swap_file->f_mapping->host; >>>>         mask = swapin_nr_pages(offset) - 1; >>>>       if (!mask) >>>>           goto skip; >>>> >>> Shmem will also be using this function and I don't think the inode_read_congested >>> logic is relevant for that case. >> IMHO, shmem is also relevant. As long as it is trying to readahead from swap, it should check if the underlying device is busy or not regardless of shmem or anon page. >> > I don't think your dereference inode = si->swap_file->f_mapping->host > is always safe. You should do it only when (si->flags & SWP_FS) is true. Do you mean it is not safe for swap partition? I tested with swap partition too. It looks fine. Opening block device also gets inode. Filename                                Type            Size Used    Priority /dev/sdb1                               partition 20970492        850168  -2 Thanks, Yang > > Tim