Btrfs: directory readahead

Signed-off-by: Chris Mason <chris.mason@oracle.com>

fs/btrfs/disk-io.c

@@ -5,6 +5,7 @@
 #include <linux/scatterlist.h>
 #include <linux/swap.h>
 #include <linux/radix-tree.h>
+#include <linux/file.h>
 #include "ctree.h"
 #include "disk-io.h"
 #include "transaction.h"
@@ -253,6 +254,29 @@ static struct address_space_operations btree_aops = {
 	.sync_page	= block_sync_page,
 };
 
+int readahead_tree_block(struct btrfs_root *root, u64 blocknr)
+{
+	struct buffer_head *bh = NULL;
+
+	bh = btrfs_find_create_tree_block(root, blocknr);
+	if (!bh)
+		return 0;
+	if (buffer_uptodate(bh))
+		goto done;
+	if (test_set_buffer_locked(bh))
+		goto done;
+	if (!buffer_uptodate(bh)) {
+		get_bh(bh);
+		bh->b_end_io = end_buffer_read_sync;
+		submit_bh(READ, bh);
+	} else {
+		unlock_buffer(bh);
+	}
+done:
+	brelse(bh);
+	return 0;
+}
+
 struct buffer_head *read_tree_block(struct btrfs_root *root, u64 blocknr)
 {
 	struct buffer_head *bh = NULL;
@@ -270,11 +294,14 @@ struct buffer_head *read_tree_block(struct btrfs_root *root, u64 blocknr)
 		wait_on_buffer(bh);
 		if (!buffer_uptodate(bh))
 			goto fail;
-		csum_tree_block(root, bh, 1);
 	} else {
 		unlock_buffer(bh);
 	}
 uptodate:
+	if (!buffer_checked(bh)) {
+		csum_tree_block(root, bh, 1);
+		set_buffer_checked(bh);
+	}
 	if (check_tree_block(root, bh))
 		BUG();
 	return bh;

fs/btrfs/disk-io.h

@@ -5,6 +5,11 @@
 
 #define BTRFS_SUPER_INFO_OFFSET (16 * 1024)
 
+enum btrfs_bh_state_bits {
+	BH_Checked = BH_PrivateStart,
+};
+BUFFER_FNS(Checked, checked);
+
 static inline struct btrfs_node *btrfs_buffer_node(struct buffer_head *bh)
 {
 	return (struct btrfs_node *)bh->b_data;
@@ -21,6 +26,7 @@ static inline struct btrfs_header *btrfs_buffer_header(struct buffer_head *bh)
 }
 
 struct buffer_head *read_tree_block(struct btrfs_root *root, u64 blocknr);
+int readahead_tree_block(struct btrfs_root *root, u64 blocknr);
 struct buffer_head *btrfs_find_create_tree_block(struct btrfs_root *root,
 						 u64 blocknr);
 int write_tree_block(struct btrfs_trans_handle *trans, struct btrfs_root *root,

fs/btrfs/extent-tree.c

@@ -812,6 +812,7 @@ struct buffer_head *btrfs_alloc_free_block(struct btrfs_trans_handle *trans,
 	BUG_ON(ret);
 	buf = btrfs_find_create_tree_block(root, ins.objectid);
 	set_buffer_uptodate(buf);
+	set_buffer_checked(buf);
 	set_radix_bit(&trans->transaction->dirty_pages, buf->b_page->index);
 	return buf;
 }

fs/btrfs/super.c

@@ -585,6 +585,31 @@ printk("adding new root for inode %lu root %p (found %p)\n", inode->i_ino, sub_r
 	return d_splice_alias(inode, dentry);
 }
 
+static void reada_leaves(struct btrfs_root *root, struct btrfs_path *path)
+{
+	struct btrfs_node *node;
+	int i;
+	int nritems;
+	u64 objectid;
+	u64 item_objectid;
+	u64 blocknr;
+	int slot;
+
+	if (!path->nodes[1])
+		return;
+	node = btrfs_buffer_node(path->nodes[1]);
+	slot = path->slots[1];
+	objectid = btrfs_disk_key_objectid(&node->ptrs[slot].key);
+	nritems = btrfs_header_nritems(&node->header);
+	for (i = slot; i < nritems; i++) {
+		item_objectid = btrfs_disk_key_objectid(&node->ptrs[i].key);
+		if (item_objectid != objectid)
+			break;
+		blocknr = btrfs_node_blockptr(node, i);
+		readahead_tree_block(root, blocknr);
+	}
+}
+
 static int btrfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
 {
 	struct inode *inode = filp->f_path.dentry->d_inode;
@@ -619,6 +644,7 @@ static int btrfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
 	if (ret < 0)
 		goto err;
 	advance = 0;
+	reada_leaves(root, path);
 	while(1) {
 		leaf = btrfs_buffer_leaf(path->nodes[0]);
 		nritems = btrfs_header_nritems(&leaf->header);
@@ -631,6 +657,8 @@ static int btrfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
 				leaf = btrfs_buffer_leaf(path->nodes[0]);
 				nritems = btrfs_header_nritems(&leaf->header);
 				slot = path->slots[0];
+				if (path->slots[1] == 0)
+					reada_leaves(root, path);
 			} else {
 				slot++;
 				path->slots[0]++;