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. Just does the check in vma_cluster_readahead() since swap_vma_readahead() is just used for non-rotational device which much less likely has congestion than traditional HDD. Although swap slots may be consecutive on swap partition, it still may be fragmented on swap file. This check would help to reduce excessive stall for such case. Cc: Huang Ying <ying.huang@xxxxxxxxx> Cc: Tim Chen <tim.c.chen@xxxxxxxxx> Cc: Minchan Kim <minchan@xxxxxxxxxx> Signed-off-by: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx> --- mm/swap_state.c | 4 ++++ 1 file changed, 4 insertions(+) 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; + if (inode_read_congested(inode)) + goto skip; + do_poll = false; /* Read a page_cluster sized and aligned cluster around offset. */ start_offset = offset & ~mask; -- 1.8.3.1
