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Tue, 02 Jan 2024 09:53:55 -0800 (PST) Received: from KASONG-MB2.tencent.com ([115.171.41.9]) by smtp.gmail.com with ESMTPSA id be10-20020a170902aa0a00b001d3c3d486bfsm22151969plb.163.2024.01.02.09.53.52 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Tue, 02 Jan 2024 09:53:55 -0800 (PST) From: Kairui Song To: linux-mm@kvack.org Cc: Andrew Morton , Chris Li , "Huang, Ying" , Hugh Dickins , Johannes Weiner , Matthew Wilcox , Michal Hocko , Yosry Ahmed , David Hildenbrand , linux-kernel@vger.kernel.org, Kairui Song Subject: [PATCH v2 1/9] mm/swapfile.c: add back some comment Date: Wed, 3 Jan 2024 01:53:30 +0800 Message-ID: <20240102175338.62012-2-ryncsn@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240102175338.62012-1-ryncsn@gmail.com> References: <20240102175338.62012-1-ryncsn@gmail.com> Reply-To: Kairui Song MIME-Version: 1.0 X-Rspamd-Queue-Id: BDE82A001A X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: apbzdsp7ok7jhw8c4mumcop3tggps3w4 X-HE-Tag: 1704218037-950747 X-HE-Meta: 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 LXjT6A3N 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Kairui Song Some useful comments were dropped in commit b56a2d8af914 ('mm: rid swapoff of quadratic complexity'), add them back. Signed-off-by: Kairui Song --- mm/swapfile.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/mm/swapfile.c b/mm/swapfile.c index 3eec686484ef..f7271504aa0a 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -1880,6 +1880,17 @@ static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd, folio = page_folio(page); } if (!folio) { + /* + * The entry could have been freed, and will not + * be reused since swapoff() already disabled + * allocation from here, or alloc_page() failed. + * + * We don't hold lock here, so the swap entry could be + * SWAP_MAP_BAD (when the cluster is discarding). + * Instead of fail out, We can just skip the swap + * entry because swapoff will wait for discarding + * finish anyway. + */ swp_count = READ_ONCE(si->swap_map[offset]); if (swp_count == 0 || swp_count == SWAP_MAP_BAD) continue;