X-Git-Url: https://git.kernel.dk/?a=blobdiff_plain;f=mm%2Fswapfile.c;h=0789a762ce2f49add4f8823c38ba366d88bda9e1;hb=415bfd9cdb175cf870fb173ae9d3958862de2c97;hp=596ac98051c5a50a460e8fb638e967932c5a86a5;hpb=0dceaf7c798de953c74073cc77be40b7be49abbc;p=linux-2.6-block.git

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 596ac98051c5..0789a762ce2f 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -152,6 +152,18 @@ static int __try_to_reclaim_swap(struct swap_info_struct *si,
 	return ret;
 }
 
+static inline struct swap_extent *first_se(struct swap_info_struct *sis)
+{
+	struct rb_node *rb = rb_first(&sis->swap_extent_root);
+	return rb_entry(rb, struct swap_extent, rb_node);
+}
+
+static inline struct swap_extent *next_se(struct swap_extent *se)
+{
+	struct rb_node *rb = rb_next(&se->rb_node);
+	return rb ? rb_entry(rb, struct swap_extent, rb_node) : NULL;
+}
+
 /*
  * swapon tell device that all the old swap contents can be discarded,
  * to allow the swap device to optimize its wear-levelling.
@@ -164,7 +176,7 @@ static int discard_swap(struct swap_info_struct *si)
 	int err = 0;
 
 	/* Do not discard the swap header page! */
-	se = &si->first_swap_extent;
+	se = first_se(si);
 	start_block = (se->start_block + 1) << (PAGE_SHIFT - 9);
 	nr_blocks = ((sector_t)se->nr_pages - 1) << (PAGE_SHIFT - 9);
 	if (nr_blocks) {
@@ -175,7 +187,7 @@ static int discard_swap(struct swap_info_struct *si)
 		cond_resched();
 	}
 
-	list_for_each_entry(se, &si->first_swap_extent.list, list) {
+	for (se = next_se(se); se; se = next_se(se)) {
 		start_block = se->start_block << (PAGE_SHIFT - 9);
 		nr_blocks = (sector_t)se->nr_pages << (PAGE_SHIFT - 9);
 
@@ -189,6 +201,26 @@ static int discard_swap(struct swap_info_struct *si)
 	return err;		/* That will often be -EOPNOTSUPP */
 }
 
+static struct swap_extent *
+offset_to_swap_extent(struct swap_info_struct *sis, unsigned long offset)
+{
+	struct swap_extent *se;
+	struct rb_node *rb;
+
+	rb = sis->swap_extent_root.rb_node;
+	while (rb) {
+		se = rb_entry(rb, struct swap_extent, rb_node);
+		if (offset < se->start_page)
+			rb = rb->rb_left;
+		else if (offset >= se->start_page + se->nr_pages)
+			rb = rb->rb_right;
+		else
+			return se;
+	}
+	/* It *must* be present */
+	BUG();
+}
+
 /*
  * swap allocation tell device that a cluster of swap can now be discarded,
  * to allow the swap device to optimize its wear-levelling.
@@ -196,32 +228,25 @@ static int discard_swap(struct swap_info_struct *si)
 static void discard_swap_cluster(struct swap_info_struct *si,
 				 pgoff_t start_page, pgoff_t nr_pages)
 {
-	struct swap_extent *se = si->curr_swap_extent;
-	int found_extent = 0;
+	struct swap_extent *se = offset_to_swap_extent(si, start_page);
 
 	while (nr_pages) {
-		if (se->start_page <= start_page &&
-		    start_page < se->start_page + se->nr_pages) {
-			pgoff_t offset = start_page - se->start_page;
-			sector_t start_block = se->start_block + offset;
-			sector_t nr_blocks = se->nr_pages - offset;
-
-			if (nr_blocks > nr_pages)
-				nr_blocks = nr_pages;
-			start_page += nr_blocks;
-			nr_pages -= nr_blocks;
-
-			if (!found_extent++)
-				si->curr_swap_extent = se;
-
-			start_block <<= PAGE_SHIFT - 9;
-			nr_blocks <<= PAGE_SHIFT - 9;
-			if (blkdev_issue_discard(si->bdev, start_block,
-				    nr_blocks, GFP_NOIO, 0))
-				break;
-		}
+		pgoff_t offset = start_page - se->start_page;
+		sector_t start_block = se->start_block + offset;
+		sector_t nr_blocks = se->nr_pages - offset;
+
+		if (nr_blocks > nr_pages)
+			nr_blocks = nr_pages;
+		start_page += nr_blocks;
+		nr_pages -= nr_blocks;
+
+		start_block <<= PAGE_SHIFT - 9;
+		nr_blocks <<= PAGE_SHIFT - 9;
+		if (blkdev_issue_discard(si->bdev, start_block,
+					nr_blocks, GFP_NOIO, 0))
+			break;
 
-		se = list_next_entry(se, list);
+		se = next_se(se);
 	}
 }
 
@@ -1079,12 +1104,11 @@ fail:
 static struct swap_info_struct *__swap_info_get(swp_entry_t entry)
 {
 	struct swap_info_struct *p;
-	unsigned long offset, type;
+	unsigned long offset;
 
 	if (!entry.val)
 		goto out;
-	type = swp_type(entry);
-	p = swap_type_to_swap_info(type);
+	p = swp_swap_info(entry);
 	if (!p)
 		goto bad_nofile;
 	if (!(p->flags & SWP_USED))
@@ -1187,6 +1211,69 @@ static unsigned char __swap_entry_free_locked(struct swap_info_struct *p,
 	return usage;
 }
 
+/*
+ * Check whether swap entry is valid in the swap device.  If so,
+ * return pointer to swap_info_struct, and keep the swap entry valid
+ * via preventing the swap device from being swapoff, until
+ * put_swap_device() is called.  Otherwise return NULL.
+ *
+ * The entirety of the RCU read critical section must come before the
+ * return from or after the call to synchronize_rcu() in
+ * enable_swap_info() or swapoff().  So if "si->flags & SWP_VALID" is
+ * true, the si->map, si->cluster_info, etc. must be valid in the
+ * critical section.
+ *
+ * Notice that swapoff or swapoff+swapon can still happen before the
+ * rcu_read_lock() in get_swap_device() or after the rcu_read_unlock()
+ * in put_swap_device() if there isn't any other way to prevent
+ * swapoff, such as page lock, page table lock, etc.  The caller must
+ * be prepared for that.  For example, the following situation is
+ * possible.
+ *
+ *   CPU1				CPU2
+ *   do_swap_page()
+ *     ...				swapoff+swapon
+ *     __read_swap_cache_async()
+ *       swapcache_prepare()
+ *         __swap_duplicate()
+ *           // check swap_map
+ *     // verify PTE not changed
+ *
+ * In __swap_duplicate(), the swap_map need to be checked before
+ * changing partly because the specified swap entry may be for another
+ * swap device which has been swapoff.  And in do_swap_page(), after
+ * the page is read from the swap device, the PTE is verified not
+ * changed with the page table locked to check whether the swap device
+ * has been swapoff or swapoff+swapon.
+ */
+struct swap_info_struct *get_swap_device(swp_entry_t entry)
+{
+	struct swap_info_struct *si;
+	unsigned long offset;
+
+	if (!entry.val)
+		goto out;
+	si = swp_swap_info(entry);
+	if (!si)
+		goto bad_nofile;
+
+	rcu_read_lock();
+	if (!(si->flags & SWP_VALID))
+		goto unlock_out;
+	offset = swp_offset(entry);
+	if (offset >= si->max)
+		goto unlock_out;
+
+	return si;
+bad_nofile:
+	pr_err("%s: %s%08lx\n", __func__, Bad_file, entry.val);
+out:
+	return NULL;
+unlock_out:
+	rcu_read_unlock();
+	return NULL;
+}
+
 static unsigned char __swap_entry_free(struct swap_info_struct *p,
 				       swp_entry_t entry, unsigned char usage)
 {
@@ -1358,11 +1445,18 @@ int page_swapcount(struct page *page)
 	return count;
 }
 
-int __swap_count(struct swap_info_struct *si, swp_entry_t entry)
+int __swap_count(swp_entry_t entry)
 {
+	struct swap_info_struct *si;
 	pgoff_t offset = swp_offset(entry);
+	int count = 0;
 
-	return swap_count(si->swap_map[offset]);
+	si = get_swap_device(entry);
+	if (si) {
+		count = swap_count(si->swap_map[offset]);
+		put_swap_device(si);
+	}
+	return count;
 }
 
 static int swap_swapcount(struct swap_info_struct *si, swp_entry_t entry)
@@ -1387,9 +1481,11 @@ int __swp_swapcount(swp_entry_t entry)
 	int count = 0;
 	struct swap_info_struct *si;
 
-	si = __swap_info_get(entry);
-	if (si)
+	si = get_swap_device(entry);
+	if (si) {
 		count = swap_swapcount(si, entry);
+		put_swap_device(si);
+	}
 	return count;
 }
 
@@ -1684,7 +1780,7 @@ int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p)
 			return type;
 		}
 		if (bdev == sis->bdev) {
-			struct swap_extent *se = &sis->first_swap_extent;
+			struct swap_extent *se = first_se(sis);
 
 			if (se->start_block == offset) {
 				if (bdev_p)
@@ -2161,7 +2257,6 @@ static void drain_mmlist(void)
 static sector_t map_swap_entry(swp_entry_t entry, struct block_device **bdev)
 {
 	struct swap_info_struct *sis;
-	struct swap_extent *start_se;
 	struct swap_extent *se;
 	pgoff_t offset;
 
@@ -2169,18 +2264,8 @@ static sector_t map_swap_entry(swp_entry_t entry, struct block_device **bdev)
 	*bdev = sis->bdev;
 
 	offset = swp_offset(entry);
-	start_se = sis->curr_swap_extent;
-	se = start_se;
-
-	for ( ; ; ) {
-		if (se->start_page <= offset &&
-				offset < (se->start_page + se->nr_pages)) {
-			return se->start_block + (offset - se->start_page);
-		}
-		se = list_next_entry(se, list);
-		sis->curr_swap_extent = se;
-		BUG_ON(se == start_se);		/* It *must* be present */
-	}
+	se = offset_to_swap_extent(sis, offset);
+	return se->start_block + (offset - se->start_page);
 }
 
 /*
@@ -2198,12 +2283,11 @@ sector_t map_swap_page(struct page *page, struct block_device **bdev)
  */
 static void destroy_swap_extents(struct swap_info_struct *sis)
 {
-	while (!list_empty(&sis->first_swap_extent.list)) {
-		struct swap_extent *se;
+	while (!RB_EMPTY_ROOT(&sis->swap_extent_root)) {
+		struct rb_node *rb = sis->swap_extent_root.rb_node;
+		struct swap_extent *se = rb_entry(rb, struct swap_extent, rb_node);
 
-		se = list_first_entry(&sis->first_swap_extent.list,
-				struct swap_extent, list);
-		list_del(&se->list);
+		rb_erase(rb, &sis->swap_extent_root);
 		kfree(se);
 	}
 
@@ -2219,7 +2303,7 @@ static void destroy_swap_extents(struct swap_info_struct *sis)
 
 /*
  * Add a block range (and the corresponding page range) into this swapdev's
- * extent list.  The extent list is kept sorted in page order.
+ * extent tree.
  *
  * This function rather assumes that it is called in ascending page order.
  */
@@ -2227,20 +2311,21 @@ int
 add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
 		unsigned long nr_pages, sector_t start_block)
 {
+	struct rb_node **link = &sis->swap_extent_root.rb_node, *parent = NULL;
 	struct swap_extent *se;
 	struct swap_extent *new_se;
-	struct list_head *lh;
-
-	if (start_page == 0) {
-		se = &sis->first_swap_extent;
-		sis->curr_swap_extent = se;
-		se->start_page = 0;
-		se->nr_pages = nr_pages;
-		se->start_block = start_block;
-		return 1;
-	} else {
-		lh = sis->first_swap_extent.list.prev;	/* Highest extent */
-		se = list_entry(lh, struct swap_extent, list);
+
+	/*
+	 * place the new node at the right most since the
+	 * function is called in ascending page order.
+	 */
+	while (*link) {
+		parent = *link;
+		link = &parent->rb_right;
+	}
+
+	if (parent) {
+		se = rb_entry(parent, struct swap_extent, rb_node);
 		BUG_ON(se->start_page + se->nr_pages != start_page);
 		if (se->start_block + se->nr_pages == start_block) {
 			/* Merge it */
@@ -2249,9 +2334,7 @@ add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
 		}
 	}
 
-	/*
-	 * No merge.  Insert a new extent, preserving ordering.
-	 */
+	/* No merge, insert a new extent. */
 	new_se = kmalloc(sizeof(*se), GFP_KERNEL);
 	if (new_se == NULL)
 		return -ENOMEM;
@@ -2259,7 +2342,8 @@ add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
 	new_se->nr_pages = nr_pages;
 	new_se->start_block = start_block;
 
-	list_add_tail(&new_se->list, &sis->first_swap_extent.list);
+	rb_link_node(&new_se->rb_node, parent, link);
+	rb_insert_color(&new_se->rb_node, &sis->swap_extent_root);
 	return 1;
 }
 EXPORT_SYMBOL_GPL(add_swap_extent);
@@ -2335,9 +2419,9 @@ static int swap_node(struct swap_info_struct *p)
 	return bdev ? bdev->bd_disk->node_id : NUMA_NO_NODE;
 }
 
-static void _enable_swap_info(struct swap_info_struct *p, int prio,
-				unsigned char *swap_map,
-				struct swap_cluster_info *cluster_info)
+static void setup_swap_info(struct swap_info_struct *p, int prio,
+			    unsigned char *swap_map,
+			    struct swap_cluster_info *cluster_info)
 {
 	int i;
 
@@ -2362,7 +2446,11 @@ static void _enable_swap_info(struct swap_info_struct *p, int prio,
 	}
 	p->swap_map = swap_map;
 	p->cluster_info = cluster_info;
-	p->flags |= SWP_WRITEOK;
+}
+
+static void _enable_swap_info(struct swap_info_struct *p)
+{
+	p->flags |= SWP_WRITEOK | SWP_VALID;
 	atomic_long_add(p->pages, &nr_swap_pages);
 	total_swap_pages += p->pages;
 
@@ -2389,7 +2477,17 @@ static void enable_swap_info(struct swap_info_struct *p, int prio,
 	frontswap_init(p->type, frontswap_map);
 	spin_lock(&swap_lock);
 	spin_lock(&p->lock);
-	 _enable_swap_info(p, prio, swap_map, cluster_info);
+	setup_swap_info(p, prio, swap_map, cluster_info);
+	spin_unlock(&p->lock);
+	spin_unlock(&swap_lock);
+	/*
+	 * Guarantee swap_map, cluster_info, etc. fields are valid
+	 * between get/put_swap_device() if SWP_VALID bit is set
+	 */
+	synchronize_rcu();
+	spin_lock(&swap_lock);
+	spin_lock(&p->lock);
+	_enable_swap_info(p);
 	spin_unlock(&p->lock);
 	spin_unlock(&swap_lock);
 }
@@ -2398,7 +2496,8 @@ static void reinsert_swap_info(struct swap_info_struct *p)
 {
 	spin_lock(&swap_lock);
 	spin_lock(&p->lock);
-	_enable_swap_info(p, p->prio, p->swap_map, p->cluster_info);
+	setup_swap_info(p, p->prio, p->swap_map, p->cluster_info);
+	_enable_swap_info(p);
 	spin_unlock(&p->lock);
 	spin_unlock(&swap_lock);
 }
@@ -2501,6 +2600,17 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
 
 	reenable_swap_slots_cache_unlock();
 
+	spin_lock(&swap_lock);
+	spin_lock(&p->lock);
+	p->flags &= ~SWP_VALID;		/* mark swap device as invalid */
+	spin_unlock(&p->lock);
+	spin_unlock(&swap_lock);
+	/*
+	 * wait for swap operations protected by get/put_swap_device()
+	 * to complete
+	 */
+	synchronize_rcu();
+
 	flush_work(&p->discard_work);
 
 	destroy_swap_extents(p);
@@ -2749,7 +2859,7 @@ static struct swap_info_struct *alloc_swap_info(void)
 		 * would be relying on p->type to remain valid.
 		 */
 	}
-	INIT_LIST_HEAD(&p->first_swap_extent.list);
+	p->swap_extent_root = RB_ROOT;
 	plist_node_init(&p->list, 0);
 	for_each_node(i)
 		plist_node_init(&p->avail_lists[i], 0);
@@ -3265,17 +3375,11 @@ static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
 	unsigned char has_cache;
 	int err = -EINVAL;
 
-	if (non_swap_entry(entry))
-		goto out;
-
-	p = swp_swap_info(entry);
+	p = get_swap_device(entry);
 	if (!p)
-		goto bad_file;
-
-	offset = swp_offset(entry);
-	if (unlikely(offset >= p->max))
 		goto out;
 
+	offset = swp_offset(entry);
 	ci = lock_cluster_or_swap_info(p, offset);
 
 	count = p->swap_map[offset];
@@ -3321,11 +3425,9 @@ static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
 unlock_out:
 	unlock_cluster_or_swap_info(p, ci);
 out:
+	if (p)
+		put_swap_device(p);
 	return err;
-
-bad_file:
-	pr_err("swap_dup: %s%08lx\n", Bad_file, entry.val);
-	goto out;
 }
 
 /*
@@ -3417,6 +3519,7 @@ int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask)
 	struct page *list_page;
 	pgoff_t offset;
 	unsigned char count;
+	int ret = 0;
 
 	/*
 	 * When debugging, it's easier to use __GFP_ZERO here; but it's better
@@ -3424,15 +3527,15 @@ int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask)
 	 */
 	page = alloc_page(gfp_mask | __GFP_HIGHMEM);
 
-	si = swap_info_get(entry);
+	si = get_swap_device(entry);
 	if (!si) {
 		/*
 		 * An acceptable race has occurred since the failing
-		 * __swap_duplicate(): the swap entry has been freed,
-		 * perhaps even the whole swap_map cleared for swapoff.
+		 * __swap_duplicate(): the swap device may be swapoff
 		 */
 		goto outer;
 	}
+	spin_lock(&si->lock);
 
 	offset = swp_offset(entry);
 
@@ -3450,9 +3553,8 @@ int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask)
 	}
 
 	if (!page) {
-		unlock_cluster(ci);
-		spin_unlock(&si->lock);
-		return -ENOMEM;
+		ret = -ENOMEM;
+		goto out;
 	}
 
 	/*
@@ -3504,10 +3606,11 @@ out_unlock_cont:
 out:
 	unlock_cluster(ci);
 	spin_unlock(&si->lock);
+	put_swap_device(si);
 outer:
 	if (page)
 		__free_page(page);
-	return 0;
+	return ret;
 }
 
 /*