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Mon, 30 Dec 2024 09:47:04 -0800 (PST) Received: from KASONG-MC4.tencent.com ([1.203.117.231]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-219dc9cdf25sm180687695ad.118.2024.12.30.09.47.01 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Mon, 30 Dec 2024 09:47:03 -0800 (PST) From: Kairui Song To: linux-mm@kvack.org Cc: Andrew Morton , Chris Li , Barry Song , Ryan Roberts , Hugh Dickins , Yosry Ahmed , "Huang, Ying" , Nhat Pham , Johannes Weiner , Kalesh Singh , linux-kernel@vger.kernel.org, Kairui Song Subject: [PATCH v3 08/13] mm, swap: use an enum to define all cluster flags and wrap flags changes Date: Tue, 31 Dec 2024 01:46:16 +0800 Message-ID: <20241230174621.61185-9-ryncsn@gmail.com> X-Mailer: git-send-email 2.47.1 In-Reply-To: <20241230174621.61185-1-ryncsn@gmail.com> References: <20241230174621.61185-1-ryncsn@gmail.com> Reply-To: Kairui Song MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 8AECF120018 X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: 1w8xmdz7kfmcfwphzc11itpt34sdkpc5 X-HE-Tag: 1735580759-486813 X-HE-Meta: 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 Jwlm67Xy 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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 Currently, we are only using flags to indicate which list the cluster is on. Using one bit for each list type might be a waste, as the list type grows, we will consume too many bits. Additionally, the current mixed usage of '&' and '==' is a bit confusing. Make it clean by using an enum to define all possible cluster statuses. Only an off-list cluster will have the NONE (0) flag. And use a wrapper to annotate and sanitize all flag settings and list movements. Suggested-by: Chris Li Signed-off-by: Kairui Song --- include/linux/swap.h | 17 +++++++--- mm/swapfile.c | 75 +++++++++++++++++++++++--------------------- 2 files changed, 52 insertions(+), 40 deletions(-) diff --git a/include/linux/swap.h b/include/linux/swap.h index 02120f1005d5..339d7f0192ff 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -257,10 +257,19 @@ struct swap_cluster_info { u8 order; struct list_head list; }; -#define CLUSTER_FLAG_FREE 1 /* This cluster is free */ -#define CLUSTER_FLAG_NONFULL 2 /* This cluster is on nonfull list */ -#define CLUSTER_FLAG_FRAG 4 /* This cluster is on nonfull list */ -#define CLUSTER_FLAG_FULL 8 /* This cluster is on full list */ + +/* All on-list cluster must have a non-zero flag. */ +enum swap_cluster_flags { + CLUSTER_FLAG_NONE = 0, /* For temporary off-list cluster */ + CLUSTER_FLAG_FREE, + CLUSTER_FLAG_NONFULL, + CLUSTER_FLAG_FRAG, + /* Clusters with flags above are allocatable */ + CLUSTER_FLAG_USABLE = CLUSTER_FLAG_FRAG, + CLUSTER_FLAG_FULL, + CLUSTER_FLAG_DISCARD, + CLUSTER_FLAG_MAX, +}; /* * The first page in the swap file is the swap header, which is always marked diff --git a/mm/swapfile.c b/mm/swapfile.c index 99fd0b0d84a2..7795a3d27273 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -403,7 +403,7 @@ static void discard_swap_cluster(struct swap_info_struct *si, static inline bool cluster_is_free(struct swap_cluster_info *info) { - return info->flags & CLUSTER_FLAG_FREE; + return info->flags == CLUSTER_FLAG_FREE; } static inline unsigned int cluster_index(struct swap_info_struct *si, @@ -434,6 +434,27 @@ static inline void unlock_cluster(struct swap_cluster_info *ci) spin_unlock(&ci->lock); } +static void cluster_move(struct swap_info_struct *si, + struct swap_cluster_info *ci, struct list_head *list, + enum swap_cluster_flags new_flags) +{ + VM_WARN_ON(ci->flags == new_flags); + BUILD_BUG_ON(1 << sizeof(ci->flags) * BITS_PER_BYTE < CLUSTER_FLAG_MAX); + + if (ci->flags == CLUSTER_FLAG_NONE) { + list_add_tail(&ci->list, list); + } else { + if (ci->flags == CLUSTER_FLAG_FRAG) { + VM_WARN_ON(!si->frag_cluster_nr[ci->order]); + si->frag_cluster_nr[ci->order]--; + } + list_move_tail(&ci->list, list); + } + ci->flags = new_flags; + if (new_flags == CLUSTER_FLAG_FRAG) + si->frag_cluster_nr[ci->order]++; +} + /* Add a cluster to discard list and schedule it to do discard */ static void swap_cluster_schedule_discard(struct swap_info_struct *si, struct swap_cluster_info *ci) @@ -447,10 +468,8 @@ static void swap_cluster_schedule_discard(struct swap_info_struct *si, */ memset(si->swap_map + idx * SWAPFILE_CLUSTER, SWAP_MAP_BAD, SWAPFILE_CLUSTER); - - VM_BUG_ON(ci->flags & CLUSTER_FLAG_FREE); - list_move_tail(&ci->list, &si->discard_clusters); - ci->flags = 0; + VM_BUG_ON(ci->flags == CLUSTER_FLAG_FREE); + cluster_move(si, ci, &si->discard_clusters, CLUSTER_FLAG_DISCARD); schedule_work(&si->discard_work); } @@ -458,12 +477,7 @@ static void __free_cluster(struct swap_info_struct *si, struct swap_cluster_info { lockdep_assert_held(&si->lock); lockdep_assert_held(&ci->lock); - - if (ci->flags) - list_move_tail(&ci->list, &si->free_clusters); - else - list_add_tail(&ci->list, &si->free_clusters); - ci->flags = CLUSTER_FLAG_FREE; + cluster_move(si, ci, &si->free_clusters, CLUSTER_FLAG_FREE); ci->order = 0; } @@ -479,6 +493,8 @@ static void swap_do_scheduled_discard(struct swap_info_struct *si) while (!list_empty(&si->discard_clusters)) { ci = list_first_entry(&si->discard_clusters, struct swap_cluster_info, list); list_del(&ci->list); + /* Must clear flag when taking a cluster off-list */ + ci->flags = CLUSTER_FLAG_NONE; idx = cluster_index(si, ci); spin_unlock(&si->lock); @@ -519,9 +535,6 @@ static void free_cluster(struct swap_info_struct *si, struct swap_cluster_info * lockdep_assert_held(&si->lock); lockdep_assert_held(&ci->lock); - if (ci->flags & CLUSTER_FLAG_FRAG) - si->frag_cluster_nr[ci->order]--; - /* * If the swap is discardable, prepare discard the cluster * instead of free it immediately. The cluster will be freed @@ -573,13 +586,9 @@ static void dec_cluster_info_page(struct swap_info_struct *si, return; } - if (!(ci->flags & CLUSTER_FLAG_NONFULL)) { - VM_BUG_ON(ci->flags & CLUSTER_FLAG_FREE); - if (ci->flags & CLUSTER_FLAG_FRAG) - si->frag_cluster_nr[ci->order]--; - list_move_tail(&ci->list, &si->nonfull_clusters[ci->order]); - ci->flags = CLUSTER_FLAG_NONFULL; - } + if (ci->flags != CLUSTER_FLAG_NONFULL) + cluster_move(si, ci, &si->nonfull_clusters[ci->order], + CLUSTER_FLAG_NONFULL); } static bool cluster_reclaim_range(struct swap_info_struct *si, @@ -663,11 +672,13 @@ static bool cluster_alloc_range(struct swap_info_struct *si, struct swap_cluster if (!(si->flags & SWP_WRITEOK)) return false; + VM_BUG_ON(ci->flags == CLUSTER_FLAG_NONE); + VM_BUG_ON(ci->flags > CLUSTER_FLAG_USABLE); + if (cluster_is_free(ci)) { - if (nr_pages < SWAPFILE_CLUSTER) { - list_move_tail(&ci->list, &si->nonfull_clusters[order]); - ci->flags = CLUSTER_FLAG_NONFULL; - } + if (nr_pages < SWAPFILE_CLUSTER) + cluster_move(si, ci, &si->nonfull_clusters[order], + CLUSTER_FLAG_NONFULL); ci->order = order; } @@ -675,14 +686,8 @@ static bool cluster_alloc_range(struct swap_info_struct *si, struct swap_cluster swap_range_alloc(si, nr_pages); ci->count += nr_pages; - if (ci->count == SWAPFILE_CLUSTER) { - VM_BUG_ON(!(ci->flags & - (CLUSTER_FLAG_FREE | CLUSTER_FLAG_NONFULL | CLUSTER_FLAG_FRAG))); - if (ci->flags & CLUSTER_FLAG_FRAG) - si->frag_cluster_nr[ci->order]--; - list_move_tail(&ci->list, &si->full_clusters); - ci->flags = CLUSTER_FLAG_FULL; - } + if (ci->count == SWAPFILE_CLUSTER) + cluster_move(si, ci, &si->full_clusters, CLUSTER_FLAG_FULL); return true; } @@ -821,9 +826,7 @@ static unsigned long cluster_alloc_swap_entry(struct swap_info_struct *si, int o while (!list_empty(&si->nonfull_clusters[order])) { ci = list_first_entry(&si->nonfull_clusters[order], struct swap_cluster_info, list); - list_move_tail(&ci->list, &si->frag_clusters[order]); - ci->flags = CLUSTER_FLAG_FRAG; - si->frag_cluster_nr[order]++; + cluster_move(si, ci, &si->frag_clusters[order], CLUSTER_FLAG_FRAG); offset = alloc_swap_scan_cluster(si, cluster_offset(si, ci), &found, order, usage); frags++; -- 2.47.1