1 files changed, 173 insertions, 42 deletions

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 2001ce427a1d..eb71b5d9430b 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -257,6 +257,47 @@ static inline void cluster_set_null(struct swap_cluster_info *info)
 	info->data = 0;
 }
 
+static inline struct swap_cluster_info *lock_cluster(struct swap_info_struct *si,
+						     unsigned long offset)
+{
+	struct swap_cluster_info *ci;
+
+	ci = si->cluster_info;
+	if (ci) {
+		ci += offset / SWAPFILE_CLUSTER;
+		spin_lock(&ci->lock);
+	}
+	return ci;
+}
+
+static inline void unlock_cluster(struct swap_cluster_info *ci)
+{
+	if (ci)
+		spin_unlock(&ci->lock);
+}
+
+static inline struct swap_cluster_info *lock_cluster_or_swap_info(
+	struct swap_info_struct *si,
+	unsigned long offset)
+{
+	struct swap_cluster_info *ci;
+
+	ci = lock_cluster(si, offset);
+	if (!ci)
+		spin_lock(&si->lock);
+
+	return ci;
+}
+
+static inline void unlock_cluster_or_swap_info(struct swap_info_struct *si,
+					       struct swap_cluster_info *ci)
+{
+	if (ci)
+		unlock_cluster(ci);
+	else
+		spin_unlock(&si->lock);
+}
+
 static inline bool cluster_list_empty(struct swap_cluster_list *list)
 {
 	return cluster_is_null(&list->head);
@@ -281,9 +322,17 @@ static void cluster_list_add_tail(struct swap_cluster_list *list,
 		cluster_set_next_flag(&list->head, idx, 0);
 		cluster_set_next_flag(&list->tail, idx, 0);
 	} else {
+		struct swap_cluster_info *ci_tail;
 		unsigned int tail = cluster_next(&list->tail);
 
-		cluster_set_next(&ci[tail], idx);
+		/*
+		 * Nested cluster lock, but both cluster locks are
+		 * only acquired when we held swap_info_struct->lock
+		 */
+		ci_tail = ci + tail;
+		spin_lock_nested(&ci_tail->lock, SINGLE_DEPTH_NESTING);
+		cluster_set_next(ci_tail, idx);
+		unlock_cluster(ci_tail);
 		cluster_set_next_flag(&list->tail, idx, 0);
 	}
 }
@@ -328,7 +377,7 @@ static void swap_cluster_schedule_discard(struct swap_info_struct *si,
 */
 static void swap_do_scheduled_discard(struct swap_info_struct *si)
 {
-	struct swap_cluster_info *info;
+	struct swap_cluster_info *info, *ci;
 	unsigned int idx;
 
 	info = si->cluster_info;
@@ -341,10 +390,14 @@ static void swap_do_scheduled_discard(struct swap_info_struct *si)
 				SWAPFILE_CLUSTER);
 
 		spin_lock(&si->lock);
-		cluster_set_flag(&info[idx], CLUSTER_FLAG_FREE);
+		ci = lock_cluster(si, idx * SWAPFILE_CLUSTER);
+		cluster_set_flag(ci, CLUSTER_FLAG_FREE);
+		unlock_cluster(ci);
 		cluster_list_add_tail(&si->free_clusters, info, idx);
+		ci = lock_cluster(si, idx * SWAPFILE_CLUSTER);
 		memset(si->swap_map + idx * SWAPFILE_CLUSTER,
 				0, SWAPFILE_CLUSTER);
+		unlock_cluster(ci);
 	}
 }
 
@@ -447,8 +500,9 @@ static void scan_swap_map_try_ssd_cluster(struct swap_info_struct *si,
 	unsigned long *offset, unsigned long *scan_base)
 {
 	struct percpu_cluster *cluster;
+	struct swap_cluster_info *ci;
 	bool found_free;
-	unsigned long tmp;
+	unsigned long tmp, max;
 
 new_cluster:
 	cluster = this_cpu_ptr(si->percpu_cluster);
@@ -476,14 +530,21 @@ new_cluster:
 	 * check if there is still free entry in the cluster
 	 */
 	tmp = cluster->next;
-	while (tmp < si->max && tmp < (cluster_next(&cluster->index) + 1) *
-	       SWAPFILE_CLUSTER) {
+	max = min_t(unsigned long, si->max,
+		    (cluster_next(&cluster->index) + 1) * SWAPFILE_CLUSTER);
+	if (tmp >= max) {
+		cluster_set_null(&cluster->index);
+		goto new_cluster;
+	}
+	ci = lock_cluster(si, tmp);
+	while (tmp < max) {
 		if (!si->swap_map[tmp]) {
 			found_free = true;
 			break;
 		}
 		tmp++;
 	}
+	unlock_cluster(ci);
 	if (!found_free) {
 		cluster_set_null(&cluster->index);
 		goto new_cluster;
@@ -496,6 +557,7 @@ new_cluster:
 static unsigned long scan_swap_map(struct swap_info_struct *si,
 				   unsigned char usage)
 {
+	struct swap_cluster_info *ci;
 	unsigned long offset;
 	unsigned long scan_base;
 	unsigned long last_in_cluster = 0;
@@ -572,9 +634,11 @@ checks:
 	if (offset > si->highest_bit)
 		scan_base = offset = si->lowest_bit;
 
+	ci = lock_cluster(si, offset);
 	/* reuse swap entry of cache-only swap if not busy. */
 	if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) {
 		int swap_was_freed;
+		unlock_cluster(ci);
 		spin_unlock(&si->lock);
 		swap_was_freed = __try_to_reclaim_swap(si, offset);
 		spin_lock(&si->lock);
@@ -584,8 +648,10 @@ checks:
 		goto scan; /* check next one */
 	}
 
-	if (si->swap_map[offset])
+	if (si->swap_map[offset]) {
+		unlock_cluster(ci);
 		goto scan;
+	}
 
 	if (offset == si->lowest_bit)
 		si->lowest_bit++;
@@ -601,6 +667,7 @@ checks:
 	}
 	si->swap_map[offset] = usage;
 	inc_cluster_info_page(si, si->cluster_info, offset);
+	unlock_cluster(ci);
 	si->cluster_next = offset + 1;
 	si->flags -= SWP_SCANNING;
 
@@ -731,7 +798,7 @@ swp_entry_t get_swap_page_of_type(int type)
 	return (swp_entry_t) {0};
 }
 
-static struct swap_info_struct *swap_info_get(swp_entry_t entry)
+static struct swap_info_struct *_swap_info_get(swp_entry_t entry)
 {
 	struct swap_info_struct *p;
 	unsigned long offset, type;
@@ -749,7 +816,6 @@ static struct swap_info_struct *swap_info_get(swp_entry_t entry)
 		goto bad_offset;
 	if (!p->swap_map[offset])
 		goto bad_free;
-	spin_lock(&p->lock);
 	return p;
 
 bad_free:
@@ -767,14 +833,45 @@ out:
 	return NULL;
 }
 
+static struct swap_info_struct *swap_info_get(swp_entry_t entry)
+{
+	struct swap_info_struct *p;
+
+	p = _swap_info_get(entry);
+	if (p)
+		spin_lock(&p->lock);
+	return p;
+}
+
 static unsigned char swap_entry_free(struct swap_info_struct *p,
-				     swp_entry_t entry, unsigned char usage)
+				     swp_entry_t entry, unsigned char usage,
+				     bool swap_info_locked)
 {
+	struct swap_cluster_info *ci;
 	unsigned long offset = swp_offset(entry);
 	unsigned char count;
 	unsigned char has_cache;
+	bool lock_swap_info = false;
+
+	if (!swap_info_locked) {
+		count = p->swap_map[offset];
+		if (!p->cluster_info || count == usage || count == SWAP_MAP_SHMEM) {
+lock_swap_info:
+			swap_info_locked = true;
+			lock_swap_info = true;
+			spin_lock(&p->lock);
+		}
+	}
+
+	ci = lock_cluster(p, offset);
 
 	count = p->swap_map[offset];
+
+	if (!swap_info_locked && (count == usage || count == SWAP_MAP_SHMEM)) {
+		unlock_cluster(ci);
+		goto lock_swap_info;
+	}
+
 	has_cache = count & SWAP_HAS_CACHE;
 	count &= ~SWAP_HAS_CACHE;
 
@@ -800,10 +897,15 @@ static unsigned char swap_entry_free(struct swap_info_struct *p,
 	usage = count | has_cache;
 	p->swap_map[offset] = usage;
 
+	unlock_cluster(ci);
+
 	/* free if no reference */
 	if (!usage) {
+		VM_BUG_ON(!swap_info_locked);
 		mem_cgroup_uncharge_swap(entry);
+		ci = lock_cluster(p, offset);
 		dec_cluster_info_page(p, p->cluster_info, offset);
+		unlock_cluster(ci);
 		if (offset < p->lowest_bit)
 			p->lowest_bit = offset;
 		if (offset > p->highest_bit) {
@@ -829,6 +931,9 @@ static unsigned char swap_entry_free(struct swap_info_struct *p,
 		}
 	}
 
+	if (lock_swap_info)
+		spin_unlock(&p->lock);
+
 	return usage;
 }
 
@@ -840,11 +945,9 @@ void swap_free(swp_entry_t entry)
 {
 	struct swap_info_struct *p;
 
-	p = swap_info_get(entry);
-	if (p) {
-		swap_entry_free(p, entry, 1);
-		spin_unlock(&p->lock);
-	}
+	p = _swap_info_get(entry);
+	if (p)
+		swap_entry_free(p, entry, 1, false);
 }
 
 /*
@@ -854,11 +957,9 @@ void swapcache_free(swp_entry_t entry)
 {
 	struct swap_info_struct *p;
 
-	p = swap_info_get(entry);
-	if (p) {
-		swap_entry_free(p, entry, SWAP_HAS_CACHE);
-		spin_unlock(&p->lock);
-	}
+	p = _swap_info_get(entry);
+	if (p)
+		swap_entry_free(p, entry, SWAP_HAS_CACHE, false);
 }
 
 /*
@@ -870,13 +971,17 @@ int page_swapcount(struct page *page)
 {
 	int count = 0;
 	struct swap_info_struct *p;
+	struct swap_cluster_info *ci;
 	swp_entry_t entry;
+	unsigned long offset;
 
 	entry.val = page_private(page);
-	p = swap_info_get(entry);
+	p = _swap_info_get(entry);
 	if (p) {
-		count = swap_count(p->swap_map[swp_offset(entry)]);
-		spin_unlock(&p->lock);
+		offset = swp_offset(entry);
+		ci = lock_cluster_or_swap_info(p, offset);
+		count = swap_count(p->swap_map[offset]);
+		unlock_cluster_or_swap_info(p, ci);
 	}
 	return count;
 }
@@ -889,22 +994,26 @@ int swp_swapcount(swp_entry_t entry)
 {
 	int count, tmp_count, n;
 	struct swap_info_struct *p;
+	struct swap_cluster_info *ci;
 	struct page *page;
 	pgoff_t offset;
 	unsigned char *map;
 
-	p = swap_info_get(entry);
+	p = _swap_info_get(entry);
 	if (!p)
 		return 0;
 
-	count = swap_count(p->swap_map[swp_offset(entry)]);
+	offset = swp_offset(entry);
+
+	ci = lock_cluster_or_swap_info(p, offset);
+
+	count = swap_count(p->swap_map[offset]);
 	if (!(count & COUNT_CONTINUED))
 		goto out;
 
 	count &= ~COUNT_CONTINUED;
 	n = SWAP_MAP_MAX + 1;
 
-	offset = swp_offset(entry);
 	page = vmalloc_to_page(p->swap_map + offset);
 	offset &= ~PAGE_MASK;
 	VM_BUG_ON(page_private(page) != SWP_CONTINUED);
@@ -919,7 +1028,7 @@ int swp_swapcount(swp_entry_t entry)
 		n *= (SWAP_CONT_MAX + 1);
 	} while (tmp_count & COUNT_CONTINUED);
 out:
-	spin_unlock(&p->lock);
+	unlock_cluster_or_swap_info(p, ci);
 	return count;
 }
 
@@ -1017,7 +1126,7 @@ int free_swap_and_cache(swp_entry_t entry)
 
 	p = swap_info_get(entry);
 	if (p) {
-		if (swap_entry_free(p, entry, 1) == SWAP_HAS_CACHE) {
+		if (swap_entry_free(p, entry, 1, true) == SWAP_HAS_CACHE) {
 			page = find_get_page(swap_address_space(entry),
 					     swp_offset(entry));
 			if (page && !trylock_page(page)) {
@@ -2298,6 +2407,9 @@ static unsigned long read_swap_header(struct swap_info_struct *p,
 	return maxpages;
 }
 
+#define SWAP_CLUSTER_COLS						\
+	DIV_ROUND_UP(L1_CACHE_BYTES, sizeof(struct swap_cluster_info))
+
 static int setup_swap_map_and_extents(struct swap_info_struct *p,
 					union swap_header *swap_header,
 					unsigned char *swap_map,
@@ -2305,11 +2417,12 @@ static int setup_swap_map_and_extents(struct swap_info_struct *p,
 					unsigned long maxpages,
 					sector_t *span)
 {
-	int i;
+	unsigned int j, k;
 	unsigned int nr_good_pages;
 	int nr_extents;
 	unsigned long nr_clusters = DIV_ROUND_UP(maxpages, SWAPFILE_CLUSTER);
-	unsigned long idx = p->cluster_next / SWAPFILE_CLUSTER;
+	unsigned long col = p->cluster_next / SWAPFILE_CLUSTER % SWAP_CLUSTER_COLS;
+	unsigned long i, idx;
 
 	nr_good_pages = maxpages - 1;	/* omit header page */
 
@@ -2357,15 +2470,20 @@ static int setup_swap_map_and_extents(struct swap_info_struct *p,
 	if (!cluster_info)
 		return nr_extents;
 
-	for (i = 0; i < nr_clusters; i++) {
-		if (!cluster_count(&cluster_info[idx])) {
+
+	/* Reduce false cache line sharing between cluster_info */
+	for (k = 0; k < SWAP_CLUSTER_COLS; k++) {
+		j = (k + col) % SWAP_CLUSTER_COLS;
+		for (i = 0; i < DIV_ROUND_UP(nr_clusters, SWAP_CLUSTER_COLS); i++) {
+			idx = i * SWAP_CLUSTER_COLS + j;
+			if (idx >= nr_clusters)
+				continue;
+			if (cluster_count(&cluster_info[idx]))
+				continue;
 			cluster_set_flag(&cluster_info[idx], CLUSTER_FLAG_FREE);
 			cluster_list_add_tail(&p->free_clusters, cluster_info,
 					      idx);
 		}
-		idx++;
-		if (idx == nr_clusters)
-			idx = 0;
 	}
 	return nr_extents;
 }
@@ -2468,6 +2586,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 
 	if (p->bdev && blk_queue_nonrot(bdev_get_queue(p->bdev))) {
 		int cpu;
+		unsigned long ci, nr_cluster;
 
 		p->flags |= SWP_SOLIDSTATE;
 		/*
@@ -2475,13 +2594,17 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 		 * SSD
 		 */
 		p->cluster_next = 1 + (prandom_u32() % p->highest_bit);
+		nr_cluster = DIV_ROUND_UP(maxpages, SWAPFILE_CLUSTER);
 
-		cluster_info = vzalloc(DIV_ROUND_UP(maxpages,
-			SWAPFILE_CLUSTER) * sizeof(*cluster_info));
+		cluster_info = vzalloc(nr_cluster * sizeof(*cluster_info));
 		if (!cluster_info) {
 			error = -ENOMEM;
 			goto bad_swap;
 		}
+
+		for (ci = 0; ci < nr_cluster; ci++)
+			spin_lock_init(&((cluster_info + ci)->lock));
+
 		p->percpu_cluster = alloc_percpu(struct percpu_cluster);
 		if (!p->percpu_cluster) {
 			error = -ENOMEM;
@@ -2627,6 +2750,7 @@ void si_swapinfo(struct sysinfo *val)
 static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
 {
 	struct swap_info_struct *p;
+	struct swap_cluster_info *ci;
 	unsigned long offset, type;
 	unsigned char count;
 	unsigned char has_cache;
@@ -2640,10 +2764,10 @@ static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
 		goto bad_file;
 	p = swap_info[type];
 	offset = swp_offset(entry);
-
-	spin_lock(&p->lock);
 	if (unlikely(offset >= p->max))
-		goto unlock_out;
+		goto out;
+
+	ci = lock_cluster_or_swap_info(p, offset);
 
 	count = p->swap_map[offset];
 
@@ -2686,7 +2810,7 @@ static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
 	p->swap_map[offset] = count | has_cache;
 
 unlock_out:
-	spin_unlock(&p->lock);
+	unlock_cluster_or_swap_info(p, ci);
 out:
 	return err;
 
@@ -2775,6 +2899,7 @@ EXPORT_SYMBOL_GPL(__page_file_index);
 int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask)
 {
 	struct swap_info_struct *si;
+	struct swap_cluster_info *ci;
 	struct page *head;
 	struct page *page;
 	struct page *list_page;
@@ -2798,6 +2923,9 @@ int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask)
 	}
 
 	offset = swp_offset(entry);
+
+	ci = lock_cluster(si, offset);
+
 	count = si->swap_map[offset] & ~SWAP_HAS_CACHE;
 
 	if ((count & ~COUNT_CONTINUED) != SWAP_MAP_MAX) {
@@ -2810,6 +2938,7 @@ int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask)
 	}
 
 	if (!page) {
+		unlock_cluster(ci);
 		spin_unlock(&si->lock);
 		return -ENOMEM;
 	}
@@ -2858,6 +2987,7 @@ int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask)
 	list_add_tail(&page->lru, &head->lru);
 	page = NULL;			/* now it's attached, don't free it */
 out:
+	unlock_cluster(ci);
 	spin_unlock(&si->lock);
 outer:
 	if (page)
@@ -2871,7 +3001,8 @@ outer:
  * into, carry if so, or else fail until a new continuation page is allocated;
  * when the original swap_map count is decremented from 0 with continuation,
  * borrow from the continuation and report whether it still holds more.
- * Called while __swap_duplicate() or swap_entry_free() holds swap_lock.
+ * Called while __swap_duplicate() or swap_entry_free() holds swap or cluster
+ * lock.
  */
 static bool swap_count_continued(struct swap_info_struct *si,
 				 pgoff_t offset, unsigned char count)