Revert "mm/shmem: fix shmem_swapin() race with swapoff"

This reverts commit a533a21 which is
commit 2efa33f 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@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Ying Huang <ying.huang@intel.com>
Cc: Alex Shi <alexs@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

mm/shmem.c

@@ -1696,21 +1696,14 @@ 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 : current->mm;
-	struct swap_info_struct *si;
-	struct page *page = NULL;
+	struct page *page;
 	swp_entry_t swap;
 	int error;
 
 	VM_BUG_ON(!*pagep || !xa_is_value(*pagep));
 	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) {
@@ -1772,8 +1765,6 @@ 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))
@@ -1784,9 +1775,6 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index,
 		put_page(page);
 	}
 
-	if (si)
-		put_swap_device(si);
-
 	return error;
 }