From nobody Mon Feb 9 08:54:49 2026 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 4083C3F8C3 for ; Mon, 11 Mar 2024 15:01:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710169275; cv=none; b=G5DWN0BKuKOj4rNaKS38rd48cwIofFrbCO/NA3B2I7iV98kEGTdsiWZG5+FOcutV5bW47p2hOPXZHkqdOtWcrBb22r62um4UmuOmPqlozp1Rvt/0F5GODVaGppQt6QyOrqNdbmMc9JTspeyVh/6G+mk/tV3Ik7PI9Mfp32X1GhM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710169275; c=relaxed/simple; bh=W4HTRtFPqGSJ216rvR08ho2Ee31NW0Ds9D9dPsn8EEM=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=ghaLDoaLmL1HqQ5rZhuynuulnNJzBzDkbJ04Qr40g9SqPMkC0N6O2D+iVGQkbbkLHnSF+TTFYW7g8VhcgR5QpgGOMwMbo1Qk/Ae/9cnyrTq1evSLZOfLQuKHkUdC50w2kcDtoCHHwLPBEOATyQhWxg26lKF/aybsba6iFJD3LwA= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 528DC1007; Mon, 11 Mar 2024 08:01:49 -0700 (PDT) Received: from e125769.cambridge.arm.com (e125769.cambridge.arm.com [10.1.196.27]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 6A7423F64C; Mon, 11 Mar 2024 08:01:10 -0700 (PDT) From: Ryan Roberts To: Andrew Morton , David Hildenbrand , Matthew Wilcox , Huang Ying , Gao Xiang , Yu Zhao , Yang Shi , Michal Hocko , Kefeng Wang , Barry Song <21cnbao@gmail.com>, Chris Li Cc: Ryan Roberts , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH v4 1/6] mm: swap: Remove CLUSTER_FLAG_HUGE from swap_cluster_info:flags Date: Mon, 11 Mar 2024 15:00:53 +0000 Message-Id: <20240311150058.1122862-2-ryan.roberts@arm.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20240311150058.1122862-1-ryan.roberts@arm.com> References: <20240311150058.1122862-1-ryan.roberts@arm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" As preparation for supporting small-sized THP in the swap-out path, without first needing to split to order-0, Remove the CLUSTER_FLAG_HUGE, which, when present, always implies PMD-sized THP, which is the same as the cluster size. The only use of the flag was to determine whether a swap entry refers to a single page or a PMD-sized THP in swap_page_trans_huge_swapped(). Instead of relying on the flag, we now pass in nr_pages, which originates from the folio's number of pages. This allows the logic to work for folios of any order. The one snag is that one of the swap_page_trans_huge_swapped() call sites does not have the folio. But it was only being called there to shortcut a call __try_to_reclaim_swap() in some cases. __try_to_reclaim_swap() gets the folio and (via some other functions) calls swap_page_trans_huge_swapped(). So I've removed the problematic call site and believe the new logic should be functionally equivalent. That said, removing the fast path means that we will take a reference and trylock a large folio much more often, which we would like to avoid. The next patch will solve this. Removing CLUSTER_FLAG_HUGE also means we can remove split_swap_cluster() which used to be called during folio splitting, since split_swap_cluster()'s only job was to remove the flag. Signed-off-by: Ryan Roberts --- include/linux/swap.h | 10 ---------- mm/huge_memory.c | 3 --- mm/swapfile.c | 47 ++++++++------------------------------------ 3 files changed, 8 insertions(+), 52 deletions(-) diff --git a/include/linux/swap.h b/include/linux/swap.h index 2955f7a78d8d..4a8b6c60793a 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -259,7 +259,6 @@ struct swap_cluster_info { }; #define CLUSTER_FLAG_FREE 1 /* This cluster is free */ #define CLUSTER_FLAG_NEXT_NULL 2 /* This cluster has no next cluster */ -#define CLUSTER_FLAG_HUGE 4 /* This cluster is backing a transparent huge = page */ =20 /* * We assign a cluster to each CPU, so each CPU can allocate swap entry fr= om @@ -600,15 +599,6 @@ static inline int add_swap_extent(struct swap_info_str= uct *sis, } #endif /* CONFIG_SWAP */ =20 -#ifdef CONFIG_THP_SWAP -extern int split_swap_cluster(swp_entry_t entry); -#else -static inline int split_swap_cluster(swp_entry_t entry) -{ - return 0; -} -#endif - #ifdef CONFIG_MEMCG static inline int mem_cgroup_swappiness(struct mem_cgroup *memcg) { diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 04fb994a7b0b..5298ba882d49 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2965,9 +2965,6 @@ static void __split_huge_page(struct page *page, stru= ct list_head *list, shmem_uncharge(folio->mapping->host, nr_dropped); remap_page(folio, nr); =20 - if (folio_test_swapcache(folio)) - split_swap_cluster(folio->swap); - /* * set page to its compound_head when split to non order-0 pages, so * we can skip unlocking it below, since PG_locked is transferred to diff --git a/mm/swapfile.c b/mm/swapfile.c index 1155a6304119..df1de034f6d8 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -343,18 +343,6 @@ static inline void cluster_set_null(struct swap_cluste= r_info *info) info->data =3D 0; } =20 -static inline bool cluster_is_huge(struct swap_cluster_info *info) -{ - if (IS_ENABLED(CONFIG_THP_SWAP)) - return info->flags & CLUSTER_FLAG_HUGE; - return false; -} - -static inline void cluster_clear_huge(struct swap_cluster_info *info) -{ - info->flags &=3D ~CLUSTER_FLAG_HUGE; -} - static inline struct swap_cluster_info *lock_cluster(struct swap_info_stru= ct *si, unsigned long offset) { @@ -1027,7 +1015,7 @@ static int swap_alloc_cluster(struct swap_info_struct= *si, swp_entry_t *slot) offset =3D idx * SWAPFILE_CLUSTER; ci =3D lock_cluster(si, offset); alloc_cluster(si, idx); - cluster_set_count_flag(ci, SWAPFILE_CLUSTER, CLUSTER_FLAG_HUGE); + cluster_set_count(ci, SWAPFILE_CLUSTER); =20 memset(si->swap_map + offset, SWAP_HAS_CACHE, SWAPFILE_CLUSTER); unlock_cluster(ci); @@ -1365,7 +1353,6 @@ void put_swap_folio(struct folio *folio, swp_entry_t = entry) =20 ci =3D lock_cluster_or_swap_info(si, offset); if (size =3D=3D SWAPFILE_CLUSTER) { - VM_BUG_ON(!cluster_is_huge(ci)); map =3D si->swap_map + offset; for (i =3D 0; i < SWAPFILE_CLUSTER; i++) { val =3D map[i]; @@ -1373,7 +1360,6 @@ void put_swap_folio(struct folio *folio, swp_entry_t = entry) if (val =3D=3D SWAP_HAS_CACHE) free_entries++; } - cluster_clear_huge(ci); if (free_entries =3D=3D SWAPFILE_CLUSTER) { unlock_cluster_or_swap_info(si, ci); spin_lock(&si->lock); @@ -1395,23 +1381,6 @@ void put_swap_folio(struct folio *folio, swp_entry_t= entry) unlock_cluster_or_swap_info(si, ci); } =20 -#ifdef CONFIG_THP_SWAP -int split_swap_cluster(swp_entry_t entry) -{ - struct swap_info_struct *si; - struct swap_cluster_info *ci; - unsigned long offset =3D swp_offset(entry); - - si =3D _swap_info_get(entry); - if (!si) - return -EBUSY; - ci =3D lock_cluster(si, offset); - cluster_clear_huge(ci); - unlock_cluster(ci); - return 0; -} -#endif - static int swp_entry_cmp(const void *ent1, const void *ent2) { const swp_entry_t *e1 =3D ent1, *e2 =3D ent2; @@ -1519,22 +1488,23 @@ int swp_swapcount(swp_entry_t entry) } =20 static bool swap_page_trans_huge_swapped(struct swap_info_struct *si, - swp_entry_t entry) + swp_entry_t entry, + unsigned int nr_pages) { struct swap_cluster_info *ci; unsigned char *map =3D si->swap_map; unsigned long roffset =3D swp_offset(entry); - unsigned long offset =3D round_down(roffset, SWAPFILE_CLUSTER); + unsigned long offset =3D round_down(roffset, nr_pages); int i; bool ret =3D false; =20 ci =3D lock_cluster_or_swap_info(si, offset); - if (!ci || !cluster_is_huge(ci)) { + if (!ci || nr_pages =3D=3D 1) { if (swap_count(map[roffset])) ret =3D true; goto unlock_out; } - for (i =3D 0; i < SWAPFILE_CLUSTER; i++) { + for (i =3D 0; i < nr_pages; i++) { if (swap_count(map[offset + i])) { ret =3D true; break; @@ -1556,7 +1526,7 @@ static bool folio_swapped(struct folio *folio) if (!IS_ENABLED(CONFIG_THP_SWAP) || likely(!folio_test_large(folio))) return swap_swapcount(si, entry) !=3D 0; =20 - return swap_page_trans_huge_swapped(si, entry); + return swap_page_trans_huge_swapped(si, entry, folio_nr_pages(folio)); } =20 /** @@ -1622,8 +1592,7 @@ int free_swap_and_cache(swp_entry_t entry) } =20 count =3D __swap_entry_free(p, entry); - if (count =3D=3D SWAP_HAS_CACHE && - !swap_page_trans_huge_swapped(p, entry)) + if (count =3D=3D SWAP_HAS_CACHE) __try_to_reclaim_swap(p, swp_offset(entry), TTRS_UNMAPPED | TTRS_FULL); put_swap_device(p); --=20 2.25.1