linux-kernel - Re: [v2 PATCH 1/2] mm: swap: check if swap backing device is congested or not

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Message-ID: <6878473d-3d3a-bbab-e187-f618c17db044@linux.alibaba.com>
Date:   Fri, 21 Dec 2018 10:51:11 -0800
From:   Yang Shi <yang.shi@...ux.alibaba.com>
To:     Tim Chen <tim.c.chen@...ux.intel.com>, ying.huang@...el.com,
        tim.c.chen@...el.com, minchan@...nel.org, akpm@...ux-foundation.org
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [v2 PATCH 1/2] mm: swap: check if swap backing device is
 congested or not



On 12/21/18 10:34 AM, Tim Chen wrote:
> On 12/20/18 4:21 PM, Yang Shi wrote:
>
>> --- a/mm/swap_state.c
>> +++ b/mm/swap_state.c
>> @@ -538,11 +538,17 @@ 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;
>>   
>> +	if (si->flags & (SWP_BLKDEV | SWP_FS)) {
> Maybe move the inode dereference here:
>
> 		inode = si->swap_file->f_mapping->host;

Yes, it looks better since nobody deference inode except the below code. 
Will fix in v3.

Thanks,
Yang

>
>> +		if (inode_read_congested(inode))
>> +			goto skip;
>> +	}
>> +
> Thanks.
>
> Tim