From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf1-f200.google.com (mail-pf1-f200.google.com [209.85.210.200]) by kanga.kvack.org (Postfix) with ESMTP id 62BC58E0001 for ; Wed, 19 Dec 2018 12:28:45 -0500 (EST) Received: by mail-pf1-f200.google.com with SMTP id t72so18976900pfi.21 for ; Wed, 19 Dec 2018 09:28:45 -0800 (PST) Received: from mga04.intel.com (mga04.intel.com. [192.55.52.120]) by mx.google.com with ESMTPS id d77si17148900pfj.124.2018.12.19.09.28.43 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 19 Dec 2018 09:28:43 -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> <606b73ed-da62-fdd1-71da-c4de7a02e837@linux.alibaba.com> From: Tim Chen Message-ID: Date: Wed, 19 Dec 2018 09:28:42 -0800 MIME-Version: 1.0 In-Reply-To: <606b73ed-da62-fdd1-71da-c4de7a02e837@linux.alibaba.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Yang Shi , 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 9:56 PM, Yang Shi wrote: > > > 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? The f_mapping may not be instantiated. It is only done for SWP_FS. Tim