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X-IronPort-AV: E=McAfee;i="6600,9927,10901"; a="372125897" X-IronPort-AV: E=Sophos;i="6.04,217,1695711600"; d="scan'208";a="372125897" Received: from fmviesa002.fm.intel.com ([10.60.135.142]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Nov 2023 16:38:39 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.04,217,1695711600"; d="scan'208";a="8264591" Received: from yhuang6-desk2.sh.intel.com (HELO yhuang6-desk2.ccr.corp.intel.com) ([10.238.208.55]) by fmviesa002-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Nov 2023 16:38:37 -0800 From: "Huang, Ying" To: Kairui Song Cc: linux-mm@kvack.org, Kairui Song , Andrew Morton , David Hildenbrand , Hugh Dickins , Johannes Weiner , Matthew Wilcox , Michal Hocko , linux-kernel@vger.kernel.org Subject: Re: [PATCH 16/24] mm/swap: reduce scope of get_swap_device in swapin path In-Reply-To: <20231119194740.94101-17-ryncsn@gmail.com> (Kairui Song's message of "Mon, 20 Nov 2023 03:47:32 +0800") References: <20231119194740.94101-1-ryncsn@gmail.com> <20231119194740.94101-17-ryncsn@gmail.com> Date: Wed, 22 Nov 2023 08:36:36 +0800 Message-ID: <87sf4yaajv.fsf@yhuang6-desk2.ccr.corp.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii X-Rspamd-Queue-Id: 3E633C0008 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: y4qx5f71s7zpaceub3jcpnd9ebgq3okp X-HE-Tag: 1700613521-451532 X-HE-Meta: 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 6KZyozNR PHVUs6HLHtk/4Ci5guKt5qK+PYO7Rx6eaMZoJLTTznyFaCR4nJOEnfav8glBZfgfzRF3jtP3M0BKqGK6Qy0QwjIqbXs9GqqtyJlm/IDjk7uIuMHkH9EQzUQmCdTs7GGCG/WQIuDRMb9zElR789eT2HFtMLVjaoa1aznQ90awzT405y9ecXKDQ7Nwf0ONX/T98IQ7ITvZ/eWBxrk58arJJByAbwdyFdLvK5hpRPx2QzDy2vnKn8IFJDnU8OyUEbknXT0VddquHA0VmEDW8o0nuXq2U/CNGuDnxS0fxdDkC1hIWr7P0SbFcBYjkqn4Rg0mZjA9b/UGYt3qPZN8= 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: Kairui Song writes: > From: Kairui Song > > Move get_swap_device into swapin_readahead, simplify the code > and prepare for follow up commits. No. Please don't do this. Please check the get/put_swap_device() usage rule in the comments of get_swap_device(). " * When we get a swap entry, if there aren't some other ways to * prevent swapoff, such as the folio in swap cache is locked, page * table lock is held, etc., the swap entry may become invalid because * of swapoff. Then, we need to enclose all swap related functions * with get_swap_device() and put_swap_device(), unless the swap * functions call get/put_swap_device() by themselves. " This is to simplify the reasoning about swapoff and swap entry. Why does it bother you? > For the later part in do_swap_page, using swp_swap_info directly is fine > since in that context, the swap device is pinned by swapcache reference. [snip] -- Best Regards, Huang, Ying