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Date:   Thu, 22 Jul 2021 18:31:14 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        "From: Matthew Wilcox" <willy@...radead.org>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Ying Huang <ying.huang@...el.com>, Alex Shi <alexs@...nel.org>,
        David Hildenbrand <david@...hat.com>,
        Dennis Zhou <dennis@...nel.org>,
        Hugh Dickins <hughd@...gle.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Michal Hocko <mhocko@...e.com>,
        Minchan Kim <minchan@...nel.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Wei Yang <richard.weiyang@...il.com>,
        Yang Shi <shy828301@...il.com>, Yu Zhao <yuzhao@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.10 083/125] Revert "swap: fix do_swap_page() race with swapoff"

From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

This reverts commit 8e4af3917bfc5e82f8010417c12b755ef256fa5e which is
commit 2799e77529c2a25492a4395db93996e3dacd762d upstream.

It should not have been added to the stable trees, sorry about that.

Link: https://lore.kernel.org/r/YPVgaY6uw59Fqg5x@casper.infradead.org
Reported-by: From: Matthew Wilcox <willy@...radead.org>
Cc: Miaohe Lin <linmiaohe@...wei.com>
Cc: Ying Huang <ying.huang@...el.com>
Cc: Alex Shi <alexs@...nel.org>
Cc: David Hildenbrand <david@...hat.com>
Cc: Dennis Zhou <dennis@...nel.org>
Cc: Hugh Dickins <hughd@...gle.com>
Cc: Johannes Weiner <hannes@...xchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@....com>
Cc: Matthew Wilcox <willy@...radead.org>
Cc: Michal Hocko <mhocko@...e.com>
Cc: Minchan Kim <minchan@...nel.org>
Cc: Tim Chen <tim.c.chen@...ux.intel.com>
Cc: Wei Yang <richard.weiyang@...il.com>
Cc: Yang Shi <shy828301@...il.com>
Cc: Yu Zhao <yuzhao@...gle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Sasha Levin <sashal@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 include/linux/swap.h |    9 ---------
 mm/memory.c          |   11 ++---------
 2 files changed, 2 insertions(+), 18 deletions(-)

--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -503,15 +503,6 @@ static inline struct swap_info_struct *s
 	return NULL;
 }
 
-static inline struct swap_info_struct *get_swap_device(swp_entry_t entry)
-{
-	return NULL;
-}
-
-static inline void put_swap_device(struct swap_info_struct *si)
-{
-}
-
 #define swap_address_space(entry)		(NULL)
 #define get_nr_swap_pages()			0L
 #define total_swap_pages			0L
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3302,7 +3302,6 @@ vm_fault_t do_swap_page(struct vm_fault
 {
 	struct vm_area_struct *vma = vmf->vma;
 	struct page *page = NULL, *swapcache;
-	struct swap_info_struct *si = NULL;
 	swp_entry_t entry;
 	pte_t pte;
 	int locked;
@@ -3330,16 +3329,14 @@ vm_fault_t do_swap_page(struct vm_fault
 		goto out;
 	}
 
-	/* Prevent swapoff from happening to us. */
-	si = get_swap_device(entry);
-	if (unlikely(!si))
-		goto out;
 
 	delayacct_set_flag(DELAYACCT_PF_SWAPIN);
 	page = lookup_swap_cache(entry, vma, vmf->address);
 	swapcache = page;
 
 	if (!page) {
+		struct swap_info_struct *si = swp_swap_info(entry);
+
 		if (data_race(si->flags & SWP_SYNCHRONOUS_IO) &&
 		    __swap_count(entry) == 1) {
 			/* skip swapcache */
@@ -3510,8 +3507,6 @@ vm_fault_t do_swap_page(struct vm_fault
 unlock:
 	pte_unmap_unlock(vmf->pte, vmf->ptl);
 out:
-	if (si)
-		put_swap_device(si);
 	return ret;
 out_nomap:
 	pte_unmap_unlock(vmf->pte, vmf->ptl);
@@ -3523,8 +3518,6 @@ out_release:
 		unlock_page(swapcache);
 		put_page(swapcache);
 	}
-	if (si)
-		put_swap_device(si);
 	return ret;
 }
 


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