From: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx> Subject: mm: swap: add comment for swap_vma_readahead swap_vma_readahead()'s comment is missing, just add it. Link: http://lkml.kernel.org/r/1546543673-108536-2-git-send-email-yang.shi@xxxxxxxxxxxxxxxxx Signed-off-by: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx> Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Huang Ying <ying.huang@xxxxxxxxx> Cc: Tim Chen <tim.c.chen@xxxxxxxxx> Cc: Minchan Kim <minchan@xxxxxxxxxx> Cc: Daniel Jordan <daniel.m.jordan@xxxxxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx Cc: Jens Axboe <axboe@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/swap_state.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) --- a/mm/swap_state.c~mm-swap-add-comment-for-swap_vma_readahead +++ a/mm/swap_state.c @@ -523,7 +523,7 @@ static unsigned long swapin_nr_pages(uns * This has been extended to use the NUMA policies from the mm triggering * the readahead. * - * Caller must hold down_read on the vma->vm_mm if vmf->vma is not NULL. + * Caller must hold read mmap_sem if vmf->vma is not NULL. */ struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask, struct vm_fault *vmf) @@ -698,6 +698,20 @@ static void swap_ra_info(struct vm_fault pte_unmap(orig_pte); } +/** + * swap_vma_readahead - swap in pages in hope we need them soon + * @entry: swap entry of this memory + * @gfp_mask: memory allocation flags + * @vmf: fault information + * + * Returns the struct page for entry and addr, after queueing swapin. + * + * Primitive swap readahead code. We simply read in a few pages whoes + * virtual addresses are around the fault address in the same vma. + * + * Caller must hold read mmap_sem if vmf->vma is not NULL. + * + */ static struct page *swap_vma_readahead(swp_entry_t fentry, gfp_t gfp_mask, struct vm_fault *vmf) { _
