From 18ad72f5b7186336646182b17e0654bf907b39e6 Mon Sep 17 00:00:00 2001 From: Kairui Song Date: Tue, 20 Dec 2022 02:58:38 +0800 Subject: [PATCH] swap: avoid a redundant pte map if ra window is 1 Avoid a redundant pte map/unmap when swap readahead window is 1. Link: https://lkml.kernel.org/r/20221219185840.25441-3-ryncsn@gmail.com Signed-off-by: Kairui Song Reviewed-by: "Huang, Ying" Cc: David Hildenbrand Cc: Hugh Dickins Cc: Matthew Wilcox (Oracle) Cc: Miaohe Lin Signed-off-by: Andrew Morton --- mm/swap_state.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) diff --git a/mm/swap_state.c b/mm/swap_state.c index 2927507b43d81..af8bc123b7c45 100644 --- a/mm/swap_state.c +++ b/mm/swap_state.c @@ -727,8 +727,6 @@ static void swap_ra_info(struct vm_fault *vmf, } faddr = vmf->address; - orig_pte = pte = pte_offset_map(vmf->pmd, faddr); - fpfn = PFN_DOWN(faddr); ra_val = GET_SWAP_RA_VAL(vma); pfn = PFN_DOWN(SWAP_RA_ADDR(ra_val)); @@ -739,12 +737,11 @@ static void swap_ra_info(struct vm_fault *vmf, atomic_long_set(&vma->swap_readahead_info, SWAP_RA_VAL(faddr, win, 0)); - if (win == 1) { - pte_unmap(orig_pte); + if (win == 1) return; - } /* Copy the PTEs because the page table may be unmapped */ + orig_pte = pte = pte_offset_map(vmf->pmd, faddr); if (fpfn == pfn + 1) swap_ra_clamp_pfn(vma, faddr, fpfn, fpfn + win, &start, &end); else if (pfn == fpfn + 1) -- 2.30.2