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X-IronPort-AV: E=McAfee;i="6600,9927,10961"; a="8572862" X-IronPort-AV: E=Sophos;i="6.05,214,1701158400"; d="scan'208";a="8572862" Received: from orviesa004.jf.intel.com ([10.64.159.144]) by orvoesa105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Jan 2024 01:01:04 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.05,214,1701158400"; d="scan'208";a="1589512" Received: from yhuang6-desk2.sh.intel.com (HELO yhuang6-desk2.ccr.corp.intel.com) ([10.238.208.55]) by orviesa004-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Jan 2024 01:01:01 -0800 From: "Huang, Ying" To: Yosry Ahmed Cc: Andrew Morton , Johannes Weiner , Nhat Pham , Chris Li , Chengming Zhou , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] mm: swap: update inuse_pages after all cleanups are done In-Reply-To: <20240120024007.2850671-2-yosryahmed@google.com> (Yosry Ahmed's message of "Sat, 20 Jan 2024 02:40:06 +0000") References: <20240120024007.2850671-1-yosryahmed@google.com> <20240120024007.2850671-2-yosryahmed@google.com> Date: Tue, 23 Jan 2024 16:59:03 +0800 Message-ID: <87wms0toh4.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: 44D4D80016 X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: m99k8dh4d6n5ta9bithhtio6pbz1npy5 X-HE-Tag: 1706000465-696344 X-HE-Meta: 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 dOPasQK5 ZGkFW9BncpBkFpl91w1kNRZT/xfMIjKSCXgmPef9rnQpzSL34Cesx4Ol2xrQ7S98JRqwwhKr/ji9LiTT9FxEKR/3SLPfbR0RJIeZuOtKJZ1Fr+gKtlma5s9CXAYvsSrvpfeD735nYtS1SBKJXzb0MX952AIinbPtjT0JLHCbybZjo7Sf/fDMQ+1A9vJsNRGXC3DwNAL8kov2YEyVdRHthJL56KA== 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: Yosry Ahmed writes: > In swap_range_free(), we update inuse_pages then do some cleanups (arch > invalidation, zswap invalidation, swap cache cleanups, etc). During > swapoff, try_to_unuse() uses inuse_pages to make sure all swap entries > are freed. Make sure we only update inuse_pages after we are done with > the cleanups. > > In practice, this shouldn't matter, because swap_range_free() is called > with the swap info lock held, and the swapoff code will spin for that > lock after try_to_unuse() anyway. > > The goal is to make it obvious and more future proof that once > try_to_unuse() returns, all cleanups are done. Defines "all cleanups". Apparently, some other operations are still to be done after try_to_unuse() in swap_off(). > This also facilitates a > following zswap cleanup patch which uses this fact to simplify > zswap_swapoff(). > > Signed-off-by: Yosry Ahmed > --- > mm/swapfile.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/mm/swapfile.c b/mm/swapfile.c > index 556ff7347d5f0..2fedb148b9404 100644 > --- a/mm/swapfile.c > +++ b/mm/swapfile.c > @@ -737,8 +737,6 @@ static void swap_range_free(struct swap_info_struct *si, unsigned long offset, > if (was_full && (si->flags & SWP_WRITEOK)) > add_to_avail_list(si); > } > - atomic_long_add(nr_entries, &nr_swap_pages); > - WRITE_ONCE(si->inuse_pages, si->inuse_pages - nr_entries); > if (si->flags & SWP_BLKDEV) > swap_slot_free_notify = > si->bdev->bd_disk->fops->swap_slot_free_notify; > @@ -752,6 +750,8 @@ static void swap_range_free(struct swap_info_struct *si, unsigned long offset, > offset++; > } > clear_shadow_from_swap_cache(si->type, begin, end); > + atomic_long_add(nr_entries, &nr_swap_pages); > + WRITE_ONCE(si->inuse_pages, si->inuse_pages - nr_entries); This isn't enough. You need to use smp_wmb() here and smp_rmb() in somewhere reading si->inuse_pages. > } > > static void set_cluster_next(struct swap_info_struct *si, unsigned long next) -- Best Regards, Huang, Ying