linux-kernel - [PATCH 2/3] Revert "mm/shmem: fix shmem

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Date:   Tue, 10 Aug 2021 13:29:35 -0700
From:   Yang Shi <shy828301@...il.com>
To:     hughd@...gle.com, ying.huang@...el.com, linmiaohe@...wei.com,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     shy828301@...il.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 2/3] Revert "mm/shmem: fix shmem_swapin() race with swapoff"

Due to the change about how block layer detects congestion the
justification of commit 8fd2e0b505d1 ("mm: swap: check if swap backing device
is congested or not") doesn't stand anymore, so the commit could be just
reverted in order to solve the race reported by commit 2efa33fc7f6e ("mm/shmem:
fix shmem_swapin() race with swapoff"), so the fix commit could be just
reverted as well.

Suggested-by: Hugh Dickins <hughd@...gle.com>
Cc: "Huang, Ying" <ying.huang@...el.com>
Cc: Miaohe Lin <linmiaohe@...wei.com>
Signed-off-by: Yang Shi <shy828301@...il.com>
---
 mm/shmem.c | 14 +-------------
 1 file changed, 1 insertion(+), 13 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index dcc07d14162e..d5427de5bf02 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1699,8 +1699,7 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index,
 	struct address_space *mapping = inode->i_mapping;
 	struct shmem_inode_info *info = SHMEM_I(inode);
 	struct mm_struct *charge_mm = vma ? vma->vm_mm : NULL;
-	struct swap_info_struct *si;
-	struct page *page = NULL;
+	struct page *page;
 	swp_entry_t swap;
 	int error;
 
@@ -1708,12 +1707,6 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index,
 	swap = radix_to_swp_entry(*pagep);
 	*pagep = NULL;
 
-	/* Prevent swapoff from happening to us. */
-	si = get_swap_device(swap);
-	if (!si) {
-		error = EINVAL;
-		goto failed;
-	}
 	/* Look it up and read it in.. */
 	page = lookup_swap_cache(swap, NULL, 0);
 	if (!page) {
@@ -1775,8 +1768,6 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index,
 	swap_free(swap);
 
 	*pagep = page;
-	if (si)
-		put_swap_device(si);
 	return 0;
 failed:
 	if (!shmem_confirm_swap(mapping, index, swap))
@@ -1787,9 +1778,6 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index,
 		put_page(page);
 	}
 
-	if (si)
-		put_swap_device(si);
-
 	return error;
 }
 
-- 
2.26.2