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[192.55.52.88]) by mx.google.com with ESMTPS id x9si19400973plo.98.2019.07.25.20.20.57 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 25 Jul 2019 20:20:57 -0700 (PDT) Received-SPF: pass (google.com: domain of ying.huang@intel.com designates 192.55.52.88 as permitted sender) client-ip=192.55.52.88; Authentication-Results: mx.google.com; spf=pass (google.com: domain of ying.huang@intel.com designates 192.55.52.88 as permitted sender) smtp.mailfrom=ying.huang@intel.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by fmsmga101.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 25 Jul 2019 20:20:57 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.64,309,1559545200"; d="scan'208";a="369406245" Received: from yhuang-dev.sh.intel.com (HELO yhuang-dev) ([10.239.159.29]) by fmsmga005.fm.intel.com with ESMTP; 25 Jul 2019 20:20:56 -0700 From: "Huang\, Ying" To: Matthew Wilcox Cc: Mikhail Gavrilov , huang ying , Linux List Kernel Mailing , Subject: Re: kernel BUG at mm/swap_state.c:170! References: <878ssqbj56.fsf@yhuang-dev.intel.com> <87zhl59w2t.fsf@yhuang-dev.intel.com> <20190725114408.GV363@bombadil.infradead.org> Date: Fri, 26 Jul 2019 11:20:55 +0800 In-Reply-To: <20190725114408.GV363@bombadil.infradead.org> (Matthew Wilcox's message of "Thu, 25 Jul 2019 04:44:08 -0700") Message-ID: <87a7d17a7c.fsf@yhuang-dev.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii 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: Matthew Wilcox writes: > On Tue, Jul 23, 2019 at 01:08:42PM +0800, Huang, Ying wrote: >> @@ -2489,6 +2491,14 @@ static void __split_huge_page(struct page *page, struct list_head *list, >> /* complete memcg works before add pages to LRU */ >> mem_cgroup_split_huge_fixup(head); >> >> + if (PageAnon(head) && PageSwapCache(head)) { >> + swp_entry_t entry = { .val = page_private(head) }; >> + >> + offset = swp_offset(entry); >> + swap_cache = swap_address_space(entry); >> + xa_lock(&swap_cache->i_pages); >> + } >> + >> for (i = HPAGE_PMD_NR - 1; i >= 1; i--) { >> __split_huge_page_tail(head, i, lruvec, list); >> /* Some pages can be beyond i_size: drop them from page cache */ >> @@ -2501,6 +2511,9 @@ static void __split_huge_page(struct page *page, struct list_head *list, >> } else if (!PageAnon(page)) { >> __xa_store(&head->mapping->i_pages, head[i].index, >> head + i, 0); >> + } else if (swap_cache) { >> + __xa_store(&swap_cache->i_pages, offset + i, >> + head + i, 0); > > I tried something along these lines (though I think I messed up the offset > calculation which is why it wasn't working for me). My other concern > was with the case where SWAPFILE_CLUSTER was less than HPAGE_PMD_NR. > Don't we need to drop the lock and look up a new swap_cache if offset >= > SWAPFILE_CLUSTER? In swapfile.c, there is #ifdef CONFIG_THP_SWAP #define SWAPFILE_CLUSTER HPAGE_PMD_NR ... #else #define SWAPFILE_CLUSTER 256 ... #endif So, if a THP is in swap cache, then SWAPFILE_CLUSTER equals HPAGE_PMD_NR. And there is one swap address space for each 64M swap space. So one THP will be in one swap address space. In swap.h, there is /* One swap address space for each 64M swap space */ #define SWAP_ADDRESS_SPACE_SHIFT 14 #define SWAP_ADDRESS_SPACE_PAGES (1 << SWAP_ADDRESS_SPACE_SHIFT) Best Regards, Huang, Ying