Revert "mm: swap: check if swap backing device is congested or not"

Due to the change about how block layer detects congestion the
justification of commit 8fd2e0b ("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
2efa33f ("mm/shmem: fix shmem_swapin() race with swapoff").  The
fix was reverted by the previous patch.

Link: https://lkml.kernel.org/r/20210810202936.2672-3-shy828301@gmail.com
Signed-off-by: Yang Shi <shy828301@gmail.com>
Suggested-by: Hugh Dickins <hughd@google.com>
Acked-by: Hugh Dickins <hughd@google.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/swap_state.c

@@ -628,13 +628,6 @@ struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask,
 	if (!mask)
 		goto skip;
 
-	/* Test swap type to make sure the dereference is safe */
-	if (likely(si->flags & (SWP_BLKDEV | SWP_FS_OPS))) {
-		struct inode *inode = si->swap_file->f_mapping->host;
-		if (inode_read_congested(inode))
-			goto skip;
-	}
-
 	do_poll = false;
 	/* Read a page_cluster sized and aligned cluster around offset. */
 	start_offset = offset & ~mask;