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Wed, 21 Feb 2024 13:09:11 -0800 (PST) Received: from barry-desktop.hub ([2407:7000:8942:5500:366d:9fa0:e78b:3075]) by smtp.gmail.com with ESMTPSA id l21-20020a17090aaa9500b00298c9790610sm10004596pjq.6.2024.02.21.13.09.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 21 Feb 2024 13:09:11 -0800 (PST) From: Barry Song <21cnbao@gmail.com> To: akpm@linux-foundation.org, linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, Barry Song Subject: [PATCH v2] mm/swapfile:__swap_duplicate: drop redundant WRITE_ONCE on swap_map for err cases Date: Thu, 22 Feb 2024 10:08:45 +1300 Message-Id: <20240221210845.13488-1-21cnbao@gmail.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1791544295898832646 X-GMAIL-MSGID: 1791544295898832646 From: Barry Song The code is quite hard to read, we are still writing swap_map after errors happen. Though the written value is as before, has_cache = count & SWAP_HAS_CACHE; count &= ~SWAP_HAS_CACHE; [snipped] WRITE_ONCE(p->swap_map[offset], count | has_cache); It would be better to entirely drop the WRITE_ONCE for both performance and readability. Signed-off-by: Barry Song --- -v2: drop goto according to Andrew, Thanks! mm/swapfile.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/swapfile.c b/mm/swapfile.c index 556ff7347d5f..7cb6d9a2d51d 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -3320,7 +3320,8 @@ static int __swap_duplicate(swp_entry_t entry, unsigned char usage) } else err = -ENOENT; /* unused swap entry */ - WRITE_ONCE(p->swap_map[offset], count | has_cache); + if (!err) + WRITE_ONCE(p->swap_map[offset], count | has_cache); unlock_out: unlock_cluster_or_swap_info(p, ci);