linux-kernel - [PATCH v2 4/5] mm/swap: remove confusing checking for non_swap_entry() in swap_ra

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Message-ID: <20210417094039.51711-5-linmiaohe@huawei.com>
Date:   Sat, 17 Apr 2021 05:40:38 -0400
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     <akpm@...ux-foundation.org>
CC:     <ying.huang@...el.com>, <dennis@...nel.org>,
        <tim.c.chen@...ux.intel.com>, <hughd@...gle.com>,
        <hannes@...xchg.org>, <mhocko@...e.com>, <iamjoonsoo.kim@....com>,
        <alexs@...nel.org>, <david@...hat.com>, <minchan@...nel.org>,
        <richard.weiyang@...il.com>, <linux-kernel@...r.kernel.org>,
        <linux-mm@...ck.org>, <linmiaohe@...wei.com>
Subject: [PATCH v2 4/5] mm/swap: remove confusing checking for non_swap_entry() in swap_ra_info()

While we released the pte lock, somebody else might faulted in this pte.
So we should check whether it's swap pte first to guard against such race
or swp_type would be unexpected. But the swap_entry isn't used in this
function and we will have enough checking when we really operate the PTE
entries later. So checking for non_swap_entry() is not really needed here
and should be removed to avoid confusion.

Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
---
 mm/swap_state.c | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/mm/swap_state.c b/mm/swap_state.c
index 272ea2108c9d..df5405384520 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -721,7 +721,6 @@ static void swap_ra_info(struct vm_fault *vmf,
 {
 	struct vm_area_struct *vma = vmf->vma;
 	unsigned long ra_val;
-	swp_entry_t entry;
 	unsigned long faddr, pfn, fpfn;
 	unsigned long start, end;
 	pte_t *pte, *orig_pte;
@@ -739,11 +738,6 @@ static void swap_ra_info(struct vm_fault *vmf,
 
 	faddr = vmf->address;
 	orig_pte = pte = pte_offset_map(vmf->pmd, faddr);
-	entry = pte_to_swp_entry(*pte);
-	if ((unlikely(non_swap_entry(entry)))) {
-		pte_unmap(orig_pte);
-		return;
-	}
 
 	fpfn = PFN_DOWN(faddr);
 	ra_val = GET_SWAP_RA_VAL(vma);
-- 
2.19.1