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Date: Thu, 10 Jan 2019 15:20:26 -0800 From: Andrew Morton <akpm@...ux-foundation.org> To: Yang Shi <yang.shi@...ux.alibaba.com> Cc: ying.huang@...el.com, tim.c.chen@...el.com, minchan@...nel.org, daniel.m.jordan@...cle.com, linux-mm@...ck.org, linux-kernel@...r.kernel.org Subject: Re: [v5 PATCH 1/2] mm: swap: check if swap backing device is congested or not On Fri, 4 Jan 2019 03:27:52 +0800 Yang Shi <yang.shi@...ux.alibaba.com> wrote: > Swap readahead would read in a few pages regardless if the underlying > device is busy or not. It may incur long waiting time if the device is > congested, and it may also exacerbate the congestion. > > Use inode_read_congested() to check if the underlying device is busy or > not like what file page readahead does. Get inode from swap_info_struct. > Although we can add inode information in swap_address_space > (address_space->host), it may lead some unexpected side effect, i.e. > it may break mapping_cap_account_dirty(). Using inode from > swap_info_struct seems simple and good enough. > > ... > > --- a/mm/swap_state.c > +++ b/mm/swap_state.c > @@ -538,11 +538,18 @@ 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 = NULL; > > mask = swapin_nr_pages(offset) - 1; > if (!mask) > goto skip; > > + if (si->flags & (SWP_BLKDEV | SWP_FS)) { > + inode = si->swap_file->f_mapping->host; > + if (inode_read_congested(inode)) > + goto skip; > + } > + > do_poll = false; > /* Read a page_cluster sized and aligned cluster around offset. */ > start_offset = offset & ~mask; Neater: --- a/mm/swap_state.c~mm-swap-check-if-swap-backing-device-is-congested-or-not-fix +++ a/mm/swap_state.c @@ -538,14 +538,13 @@ struct page *swap_cluster_readahead(swp_ bool do_poll = true, page_allocated; struct vm_area_struct *vma = vmf->vma; unsigned long addr = vmf->address; - struct inode *inode = NULL; mask = swapin_nr_pages(offset) - 1; if (!mask) goto skip; if (si->flags & (SWP_BLKDEV | SWP_FS)) { - inode = si->swap_file->f_mapping->host; + struct inode *inode = si->swap_file->f_mapping->host; if (inode_read_congested(inode)) goto skip; } _
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