Re: [RFC PATCH 1/2] mm: swap: check if swap backing device is congested or not

[Tim Chen <tim.c.chen@linux.intel.com>]

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.

So probably change the check to

	if (swp_type(entry) < nr_swapfiles &&
	    inode_read_congested(si->swap_file->f_mapping->host))
		goto skip;
		
> +	if (inode_read_congested(inode))
> +		goto skip;
> +
>  	do_poll = false;
>  	/* Read a page_cluster sized and aligned cluster around offset. */
>  	start_offset = offset & ~mask;
> 

Thanks.

Tim