linux-kernel - [PATCH 3/3] Revert "mm: swap: check if swap backing device is congested or not"

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Date:   Tue, 10 Aug 2021 13:29:36 -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 3/3] 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 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"). The fix was reverted by the
previous patch.

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/swap_state.c | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/mm/swap_state.c b/mm/swap_state.c
index 1a29b4f98208..8d4104242100 100644
--- a/mm/swap_state.c
+++ b/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;
-- 
2.26.2