Btrfs: cache values for locking extents

Many of the btrfs extent state tree users follow the same pattern.
They lock an extent range in the tree, do some operation and then
unlock.

This translates to at least 2 rbtree searches, and maybe more if they
are doing operations on the extent state tree.  A locked extent
in the tree isn't going to be merged or changed, and so we can
safely return the extent state structure as a cached handle.

This changes set_extent_bit to give back a cached handle, and also
changes both set_extent_bit and clear_extent_bit to use the cached
handle if it is available.
Signed-off-by: Chris Mason <chris.mason@oracle.com>

fs/btrfs/extent_io.c

@@ -471,10 +471,14 @@ static int clear_state_bit(struct extent_io_tree *tree,
  * bits were already set, or zero if none of the bits were already set.
  */
 int clear_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
-		     int bits, int wake, int delete, gfp_t mask)
+		     int bits, int wake, int delete,
+		     struct extent_state **cached_state,
+		     gfp_t mask)
 {
 	struct extent_state *state;
+	struct extent_state *cached;
 	struct extent_state *prealloc = NULL;
+	struct rb_node *next_node;
 	struct rb_node *node;
 	u64 last_end;
 	int err;
@@ -488,6 +492,17 @@ again:
 	}
 
 	spin_lock(&tree->lock);
+	if (cached_state) {
+		cached = *cached_state;
+		*cached_state = NULL;
+		if (cached->tree && cached->start == start) {
+			atomic_dec(&cached->refs);
+			state = cached;
+			last_end = state->end;
+			goto found;
+		}
+		free_extent_state(cached);
+	}
 	/*
 	 * this search will find the extents that end after
 	 * our range starts
@@ -496,6 +511,7 @@ again:
 	if (!node)
 		goto out;
 	state = rb_entry(node, struct extent_state, rb_node);
+hit_next:
 	if (state->start > end)
 		goto out;
 	WARN_ON(state->end < start);
@@ -555,11 +571,21 @@ again:
 		prealloc = NULL;
 		goto out;
 	}
-
+found:
+	if (state->end < end && prealloc && !need_resched())
+		next_node = rb_next(&state->rb_node);
+	else
+		next_node = NULL;
 	set |= clear_state_bit(tree, state, bits, wake, delete);
 	if (last_end == (u64)-1)
 		goto out;
 	start = last_end + 1;
+	if (start <= end && next_node) {
+		state = rb_entry(next_node, struct extent_state,
+				 rb_node);
+		if (state->start == start)
+			goto hit_next;
+	}
 	goto search_again;
 
 out:
@@ -653,6 +679,17 @@ static void set_state_bits(struct extent_io_tree *tree,
 	state->state |= bits;
 }
 
+static void cache_state(struct extent_state *state,
+			struct extent_state **cached_ptr)
+{
+	if (cached_ptr && !(*cached_ptr)) {
+		if (state->state & (EXTENT_IOBITS | EXTENT_BOUNDARY)) {
+			*cached_ptr = state;
+			atomic_inc(&state->refs);
+		}
+	}
+}
+
 /*
  * set some bits on a range in the tree.  This may require allocations or
  * sleeping, so the gfp mask is used to indicate what is allowed.
@@ -666,6 +703,7 @@ static void set_state_bits(struct extent_io_tree *tree,
 
 static int set_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
 			  int bits, int exclusive_bits, u64 *failed_start,
+			  struct extent_state **cached_state,
 			  gfp_t mask)
 {
 	struct extent_state *state;
@@ -712,6 +750,7 @@ hit_next:
 			goto out;
 		}
 		set_state_bits(tree, state, bits);
+		cache_state(state, cached_state);
 		merge_state(tree, state);
 		if (last_end == (u64)-1)
 			goto out;
@@ -758,6 +797,7 @@ hit_next:
 			goto out;
 		if (state->end <= end) {
 			set_state_bits(tree, state, bits);
+			cache_state(state, cached_state);
 			merge_state(tree, state);
 			if (last_end == (u64)-1)
 				goto out;
@@ -782,6 +822,7 @@ hit_next:
 			this_end = last_start - 1;
 		err = insert_state(tree, prealloc, start, this_end,
 				   bits);
+		cache_state(prealloc, cached_state);
 		prealloc = NULL;
 		BUG_ON(err == -EEXIST);
 		if (err)
@@ -805,6 +846,7 @@ hit_next:
 		BUG_ON(err == -EEXIST);
 
 		set_state_bits(tree, prealloc, bits);
+		cache_state(prealloc, cached_state);
 		merge_state(tree, prealloc);
 		prealloc = NULL;
 		goto out;
@@ -833,26 +875,27 @@ int set_extent_dirty(struct extent_io_tree *tree, u64 start, u64 end,
 		     gfp_t mask)
 {
 	return set_extent_bit(tree, start, end, EXTENT_DIRTY, 0, NULL,
-			      mask);
+			      NULL, mask);
 }
 
 int set_extent_ordered(struct extent_io_tree *tree, u64 start, u64 end,
 		       gfp_t mask)
 {
-	return set_extent_bit(tree, start, end, EXTENT_ORDERED, 0, NULL, mask);
+	return set_extent_bit(tree, start, end, EXTENT_ORDERED, 0, NULL, NULL,
+			      mask);
 }
 
 int set_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
 		    int bits, gfp_t mask)
 {
 	return set_extent_bit(tree, start, end, bits, 0, NULL,
-			      mask);
+			      NULL, mask);
 }
 
 int clear_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
 		      int bits, gfp_t mask)
 {
-	return clear_extent_bit(tree, start, end, bits, 0, 0, mask);
+	return clear_extent_bit(tree, start, end, bits, 0, 0, NULL, mask);
 }
 
 int set_extent_delalloc(struct extent_io_tree *tree, u64 start, u64 end,
@@ -860,46 +903,50 @@ int set_extent_delalloc(struct extent_io_tree *tree, u64 start, u64 end,
 {
 	return set_extent_bit(tree, start, end,
 			      EXTENT_DELALLOC | EXTENT_DIRTY | EXTENT_UPTODATE,
-			      0, NULL, mask);
+			      0, NULL, NULL, mask);
 }
 
 int clear_extent_dirty(struct extent_io_tree *tree, u64 start, u64 end,
 		       gfp_t mask)
 {
 	return clear_extent_bit(tree, start, end,
-				EXTENT_DIRTY | EXTENT_DELALLOC, 0, 0, mask);
+				EXTENT_DIRTY | EXTENT_DELALLOC, 0, 0,
+				NULL, mask);
 }
 
 int clear_extent_ordered(struct extent_io_tree *tree, u64 start, u64 end,
 			 gfp_t mask)
 {
-	return clear_extent_bit(tree, start, end, EXTENT_ORDERED, 1, 0, mask);
+	return clear_extent_bit(tree, start, end, EXTENT_ORDERED, 1, 0,
+				NULL, mask);
 }
 
 int set_extent_new(struct extent_io_tree *tree, u64 start, u64 end,
 		     gfp_t mask)
 {
 	return set_extent_bit(tree, start, end, EXTENT_NEW, 0, NULL,
-			      mask);
+			      NULL, mask);
 }
 
 static int clear_extent_new(struct extent_io_tree *tree, u64 start, u64 end,
 		       gfp_t mask)
 {
-	return clear_extent_bit(tree, start, end, EXTENT_NEW, 0, 0, mask);
+	return clear_extent_bit(tree, start, end, EXTENT_NEW, 0, 0,
+				NULL, mask);
 }
 
 int set_extent_uptodate(struct extent_io_tree *tree, u64 start, u64 end,
 			gfp_t mask)
 {
 	return set_extent_bit(tree, start, end, EXTENT_UPTODATE, 0, NULL,
-			      mask);
+			      NULL, mask);
 }
 
 static int clear_extent_uptodate(struct extent_io_tree *tree, u64 start,
 				 u64 end, gfp_t mask)
 {
-	return clear_extent_bit(tree, start, end, EXTENT_UPTODATE, 0, 0, mask);
+	return clear_extent_bit(tree, start, end, EXTENT_UPTODATE, 0, 0,
+				NULL, mask);
 }
 
 int wait_on_extent_writeback(struct extent_io_tree *tree, u64 start, u64 end)
@@ -912,13 +959,14 @@ int wait_on_extent_writeback(struct extent_io_tree *tree, u64 start, u64 end)
  * us if waiting is desired.
  */
 int lock_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
-		     int bits, gfp_t mask)
+		     int bits, struct extent_state **cached_state, gfp_t mask)
 {
 	int err;
 	u64 failed_start;
 	while (1) {
 		err = set_extent_bit(tree, start, end, EXTENT_LOCKED | bits,
-				     EXTENT_LOCKED, &failed_start, mask);
+				     EXTENT_LOCKED, &failed_start,
+				     cached_state, mask);
 		if (err == -EEXIST && (mask & __GFP_WAIT)) {
 			wait_extent_bit(tree, failed_start, end, EXTENT_LOCKED);
 			start = failed_start;
@@ -932,7 +980,7 @@ int lock_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
 
 int lock_extent(struct extent_io_tree *tree, u64 start, u64 end, gfp_t mask)
 {
-	return lock_extent_bits(tree, start, end, 0, mask);
+	return lock_extent_bits(tree, start, end, 0, NULL, mask);
 }
 
 int try_lock_extent(struct extent_io_tree *tree, u64 start, u64 end,
@@ -941,21 +989,29 @@ int try_lock_extent(struct extent_io_tree *tree, u64 start, u64 end,
 	int err;
 	u64 failed_start;
 
-	err = set_extent_bit(tree, start, end, EXTENT_LOCKED, 1,
-			     &failed_start, mask);
+	err = set_extent_bit(tree, start, end, EXTENT_LOCKED, EXTENT_LOCKED,
+			     &failed_start, NULL, mask);
 	if (err == -EEXIST) {
 		if (failed_start > start)
 			clear_extent_bit(tree, start, failed_start - 1,
-					 EXTENT_LOCKED, 1, 0, mask);
+					 EXTENT_LOCKED, 1, 0, NULL, mask);
 		return 0;
 	}
 	return 1;
 }
 
+int unlock_extent_cached(struct extent_io_tree *tree, u64 start, u64 end,
+			 struct extent_state **cached, gfp_t mask)
+{
+	return clear_extent_bit(tree, start, end, EXTENT_LOCKED, 1, 0, cached,
+				mask);
+}
+
 int unlock_extent(struct extent_io_tree *tree, u64 start, u64 end,
 		  gfp_t mask)
 {
-	return clear_extent_bit(tree, start, end, EXTENT_LOCKED, 1, 0, mask);
+	return clear_extent_bit(tree, start, end, EXTENT_LOCKED, 1, 0, NULL,
+				mask);
 }
 
 /*
@@ -1323,7 +1379,7 @@ int extent_clear_unlock_delalloc(struct inode *inode,
 	if (clear_delalloc)
 		clear_bits |= EXTENT_DELALLOC;
 
-	clear_extent_bit(tree, start, end, clear_bits, 1, 0, GFP_NOFS);
+	clear_extent_bit(tree, start, end, clear_bits, 1, 0, NULL, GFP_NOFS);
 	if (!(unlock_pages || clear_dirty || set_writeback || end_writeback))
 		return 0;
 
@@ -2071,6 +2127,7 @@ static int __extent_writepage(struct page *page, struct writeback_control *wbc,
 	u64 iosize;
 	u64 unlock_start;
 	sector_t sector;
+	struct extent_state *cached_state = NULL;
 	struct extent_map *em;
 	struct block_device *bdev;
 	int ret;
@@ -2162,7 +2219,7 @@ static int __extent_writepage(struct page *page, struct writeback_control *wbc,
 			goto done_unlocked;
 		}
 	}
-	lock_extent(tree, start, page_end, GFP_NOFS);
+	lock_extent_bits(tree, start, page_end, 0, &cached_state, GFP_NOFS);
 
 	unlock_start = start;
 
@@ -2170,7 +2227,8 @@ static int __extent_writepage(struct page *page, struct writeback_control *wbc,
 		ret = tree->ops->writepage_start_hook(page, start,
 						      page_end);
 		if (ret == -EAGAIN) {
-			unlock_extent(tree, start, page_end, GFP_NOFS);
+			unlock_extent_cached(tree, start, page_end,
+					     &cached_state, GFP_NOFS);
 			redirty_page_for_writepage(wbc, page);
 			update_nr_written(page, wbc, nr_written);
 			unlock_page(page);
@@ -2192,7 +2250,7 @@ static int __extent_writepage(struct page *page, struct writeback_control *wbc,
 	if (last_byte <= start) {
 		clear_extent_bit(tree, start, page_end,
 				 EXTENT_LOCKED | EXTENT_DIRTY,
-				 1, 0, GFP_NOFS);
+				 1, 0, NULL, GFP_NOFS);
 		if (tree->ops && tree->ops->writepage_end_io_hook)
 			tree->ops->writepage_end_io_hook(page, start,
 							 page_end, NULL, 1);
@@ -2204,7 +2262,8 @@ static int __extent_writepage(struct page *page, struct writeback_control *wbc,
 
 	while (cur <= end) {
 		if (cur >= last_byte) {
-			unlock_extent(tree, unlock_start, page_end, GFP_NOFS);
+			unlock_extent_cached(tree, unlock_start, page_end,
+					     &cached_state, GFP_NOFS);
 			if (tree->ops && tree->ops->writepage_end_io_hook)
 				tree->ops->writepage_end_io_hook(page, cur,
 							 page_end, NULL, 1);
@@ -2236,8 +2295,9 @@ static int __extent_writepage(struct page *page, struct writeback_control *wbc,
 		 */
 		if (compressed || block_start == EXTENT_MAP_HOLE ||
 		    block_start == EXTENT_MAP_INLINE) {
-			unlock_extent(tree, unlock_start, cur + iosize - 1,
-				      GFP_NOFS);
+			unlock_extent_cached(tree, unlock_start,
+					     cur + iosize - 1, &cached_state,
+					     GFP_NOFS);
 
 			/*
 			 * end_io notification does not happen here for
@@ -2307,11 +2367,14 @@ done:
 		end_page_writeback(page);
 	}
 	if (unlock_start <= page_end)
-		unlock_extent(tree, unlock_start, page_end, GFP_NOFS);
+		unlock_extent_cached(tree, unlock_start, page_end,
+				     &cached_state, GFP_NOFS);
 	unlock_page(page);
 
 done_unlocked:
 
+	/* drop our reference on any cached states */
+	free_extent_state(cached_state);
 	return 0;
 }
 
@@ -2599,7 +2662,7 @@ int extent_invalidatepage(struct extent_io_tree *tree,
 	wait_on_page_writeback(page);
 	clear_extent_bit(tree, start, end,
 			 EXTENT_LOCKED | EXTENT_DIRTY | EXTENT_DELALLOC,
-			 1, 1, GFP_NOFS);
+			 1, 1, NULL, GFP_NOFS);
 	return 0;
 }
 
@@ -2693,7 +2756,7 @@ int extent_prepare_write(struct extent_io_tree *tree,
 			 */
 			set_extent_bit(tree, block_start,
 				       block_start + iosize - 1,
-				       EXTENT_LOCKED, 0, NULL, GFP_NOFS);
+				       EXTENT_LOCKED, 0, NULL, NULL, GFP_NOFS);
 			ret = submit_extent_page(READ, tree, page,
 					 sector, iosize, page_offset, em->bdev,
 					 NULL, 1,
@@ -2740,7 +2803,7 @@ int try_release_extent_state(struct extent_map_tree *map,
 		if ((mask & GFP_NOFS) == GFP_NOFS)
 			mask = GFP_NOFS;
 		clear_extent_bit(tree, start, end, EXTENT_UPTODATE,
-				 1, 1, mask);
+				 1, 1, NULL, mask);
 	}
 	return ret;
 }

fs/btrfs/extent_io.h

@@ -143,7 +143,7 @@ int try_release_extent_state(struct extent_map_tree *map,
 			     gfp_t mask);
 int lock_extent(struct extent_io_tree *tree, u64 start, u64 end, gfp_t mask);
 int lock_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
-		     int bits, gfp_t mask);
+		     int bits, struct extent_state **cached, gfp_t mask);
 int unlock_extent(struct extent_io_tree *tree, u64 start, u64 end, gfp_t mask);
 int try_lock_extent(struct extent_io_tree *tree, u64 start, u64 end,
 		    gfp_t mask);
@@ -161,7 +161,8 @@ int test_range_bit(struct extent_io_tree *tree, u64 start, u64 end,
 int clear_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
 		      int bits, gfp_t mask);
 int clear_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
-		     int bits, int wake, int delete, gfp_t mask);
+		     int bits, int wake, int delete, struct extent_state **cached,
+		     gfp_t mask);
 int set_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
 		    int bits, gfp_t mask);
 int set_extent_uptodate(struct extent_io_tree *tree, u64 start, u64 end,

fs/btrfs/inode.c

@@ -854,7 +854,7 @@ static int cow_file_range_async(struct inode *inode, struct page *locked_page,
 	int limit = 10 * 1024 * 1042;
 
 	clear_extent_bit(&BTRFS_I(inode)->io_tree, start, end, EXTENT_LOCKED |
-			 EXTENT_DELALLOC, 1, 0, GFP_NOFS);
+			 EXTENT_DELALLOC, 1, 0, NULL, GFP_NOFS);
 	while (start < end) {
 		async_cow = kmalloc(sizeof(*async_cow), GFP_NOFS);
 		async_cow->inode = inode;
@@ -4420,7 +4420,7 @@ static void btrfs_invalidatepage(struct page *page, unsigned long offset)
 		 */
 		clear_extent_bit(tree, page_start, page_end,
 				 EXTENT_DIRTY | EXTENT_DELALLOC |
-				 EXTENT_LOCKED, 1, 0, GFP_NOFS);
+				 EXTENT_LOCKED, 1, 0, NULL, GFP_NOFS);
 		btrfs_finish_ordered_io(page->mapping->host,
 					page_start, page_end);
 		btrfs_put_ordered_extent(ordered);
@@ -4429,7 +4429,7 @@ static void btrfs_invalidatepage(struct page *page, unsigned long offset)
 	clear_extent_bit(tree, page_start, page_end,
 		 EXTENT_LOCKED | EXTENT_DIRTY | EXTENT_DELALLOC |
 		 EXTENT_ORDERED,
-		 1, 1, GFP_NOFS);
+		 1, 1, NULL, GFP_NOFS);
 	__btrfs_releasepage(page, GFP_NOFS);
 
 	ClearPageChecked(page);