Btrfs: add initial tracepoint support for btrfs

Tracepoints can provide insight into why btrfs hits bugs and be greatly
helpful for debugging, e.g
              dd-7822  [000]  2121.641088: btrfs_inode_request: root = 5(FS_TREE), gen = 4, ino = 256, blocks = 8, disk_i_size = 0, last_trans = 8, logged_trans = 0
              dd-7822  [000]  2121.641100: btrfs_inode_new: root = 5(FS_TREE), gen = 8, ino = 257, blocks = 0, disk_i_size = 0, last_trans = 0, logged_trans = 0
 btrfs-transacti-7804  [001]  2146.935420: btrfs_cow_block: root = 2(EXTENT_TREE), refs = 2, orig_buf = 29368320 (orig_level = 0), cow_buf = 29388800 (cow_level = 0)
 btrfs-transacti-7804  [001]  2146.935473: btrfs_cow_block: root = 1(ROOT_TREE), refs = 2, orig_buf = 29364224 (orig_level = 0), cow_buf = 29392896 (cow_level = 0)
 btrfs-transacti-7804  [001]  2146.972221: btrfs_transaction_commit: root = 1(ROOT_TREE), gen = 8
   flush-btrfs-2-7821  [001]  2155.824210: btrfs_chunk_alloc: root = 3(CHUNK_TREE), offset = 1103101952, size = 1073741824, num_stripes = 1, sub_stripes = 0, type = DATA
   flush-btrfs-2-7821  [001]  2155.824241: btrfs_cow_block: root = 2(EXTENT_TREE), refs = 2, orig_buf = 29388800 (orig_level = 0), cow_buf = 29396992 (cow_level = 0)
   flush-btrfs-2-7821  [001]  2155.824255: btrfs_cow_block: root = 4(DEV_TREE), refs = 2, orig_buf = 29372416 (orig_level = 0), cow_buf = 29401088 (cow_level = 0)
   flush-btrfs-2-7821  [000]  2155.824329: btrfs_cow_block: root = 3(CHUNK_TREE), refs = 2, orig_buf = 20971520 (orig_level = 0), cow_buf = 20975616 (cow_level = 0)
 btrfs-endio-wri-7800  [001]  2155.898019: btrfs_cow_block: root = 5(FS_TREE), refs = 2, orig_buf = 29384704 (orig_level = 0), cow_buf = 29405184 (cow_level = 0)
 btrfs-endio-wri-7800  [001]  2155.898043: btrfs_cow_block: root = 7(CSUM_TREE), refs = 2, orig_buf = 29376512 (orig_level = 0), cow_buf = 29409280 (cow_level = 0)

Here is what I have added:

1) ordere_extent:
        btrfs_ordered_extent_add
        btrfs_ordered_extent_remove
        btrfs_ordered_extent_start
        btrfs_ordered_extent_put

These provide critical information to understand how ordered_extents are
updated.

2) extent_map:
        btrfs_get_extent

extent_map is used in both read and write cases, and it is useful for tracking
how btrfs specific IO is running.

3) writepage:
        __extent_writepage
        btrfs_writepage_end_io_hook

Pages are cirtical resourses and produce a lot of corner cases during writeback,
so it is valuable to know how page is written to disk.

4) inode:
        btrfs_inode_new
        btrfs_inode_request
        btrfs_inode_evict

These can show where and when a inode is created, when a inode is evicted.

5) sync:
        btrfs_sync_file
        btrfs_sync_fs

These show sync arguments.

6) transaction:
        btrfs_transaction_commit

In transaction based filesystem, it will be useful to know the generation and
who does commit.

7) back reference and cow:
	btrfs_delayed_tree_ref
	btrfs_delayed_data_ref
	btrfs_delayed_ref_head
	btrfs_cow_block

Btrfs natively supports back references, these tracepoints are helpful on
understanding btrfs's COW mechanism.

8) chunk:
	btrfs_chunk_alloc
	btrfs_chunk_free

Chunk is a link between physical offset and logical offset, and stands for space
infomation in btrfs, and these are helpful on tracing space things.

9) reserved_extent:
	btrfs_reserved_extent_alloc
	btrfs_reserved_extent_free

These can show how btrfs uses its space.
Signed-off-by: Liu Bo <liubo2009@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

fs/btrfs/ctree.c

@@ -535,6 +535,9 @@ noinline int btrfs_cow_block(struct btrfs_trans_handle *trans,
 
 	ret = __btrfs_cow_block(trans, root, buf, parent,
 				 parent_slot, cow_ret, search_start, 0);
+
+	trace_btrfs_cow_block(root, buf, *cow_ret);
+
 	return ret;
 }
 

fs/btrfs/ctree.h

@@ -28,6 +28,7 @@
 #include <linux/wait.h>
 #include <linux/slab.h>
 #include <linux/kobject.h>
+#include <trace/events/btrfs.h>
 #include <asm/kmap_types.h>
 #include "extent_io.h"
 #include "extent_map.h"

fs/btrfs/delayed-ref.c

@@ -483,6 +483,8 @@ static noinline int add_delayed_ref_head(struct btrfs_trans_handle *trans,
 	INIT_LIST_HEAD(&head_ref->cluster);
 	mutex_init(&head_ref->mutex);
 
+	trace_btrfs_delayed_ref_head(ref, head_ref, action);
+
 	existing = tree_insert(&delayed_refs->root, &ref->rb_node);
 
 	if (existing) {
@@ -537,6 +539,8 @@ static noinline int add_delayed_tree_ref(struct btrfs_trans_handle *trans,
 	}
 	full_ref->level = level;
 
+	trace_btrfs_delayed_tree_ref(ref, full_ref, action);
+
 	existing = tree_insert(&delayed_refs->root, &ref->rb_node);
 
 	if (existing) {
@@ -591,6 +595,8 @@ static noinline int add_delayed_data_ref(struct btrfs_trans_handle *trans,
 	full_ref->objectid = owner;
 	full_ref->offset = offset;
 
+	trace_btrfs_delayed_data_ref(ref, full_ref, action);
+
 	existing = tree_insert(&delayed_refs->root, &ref->rb_node);
 
 	if (existing) {

fs/btrfs/extent-tree.c

@@ -5412,6 +5412,8 @@ int btrfs_reserve_extent(struct btrfs_trans_handle *trans,
 		dump_space_info(sinfo, num_bytes, 1);
 	}
 
+	trace_btrfs_reserved_extent_alloc(root, ins->objectid, ins->offset);
+
 	return ret;
 }
 
@@ -5433,6 +5435,8 @@ int btrfs_free_reserved_extent(struct btrfs_root *root, u64 start, u64 len)
 	update_reserved_bytes(cache, len, 0, 1);
 	btrfs_put_block_group(cache);
 
+	trace_btrfs_reserved_extent_free(root, start, len);
+
 	return ret;
 }
 

fs/btrfs/extent_io.c

@@ -2192,6 +2192,8 @@ static int __extent_writepage(struct page *page, struct writeback_control *wbc,
 	else
 		write_flags = WRITE;
 
+	trace___extent_writepage(page, inode, wbc);
+
 	WARN_ON(!PageLocked(page));
 	pg_offset = i_size & (PAGE_CACHE_SIZE - 1);
 	if (page->index > end_index ||

fs/btrfs/file.c

@@ -1205,6 +1205,7 @@ int btrfs_sync_file(struct file *file, int datasync)
 	int ret = 0;
 	struct btrfs_trans_handle *trans;
 
+	trace_btrfs_sync_file(file, datasync);
 
 	/* we wait first, since the writeback may change the inode */
 	root->log_batch++;

fs/btrfs/inode.c

@@ -1787,6 +1787,8 @@ static int btrfs_finish_ordered_io(struct inode *inode, u64 start, u64 end)
 static int btrfs_writepage_end_io_hook(struct page *page, u64 start, u64 end,
 				struct extent_state *state, int uptodate)
 {
+	trace_btrfs_writepage_end_io_hook(page, start, end, uptodate);
+
 	ClearPagePrivate2(page);
 	return btrfs_finish_ordered_io(page->mapping->host, start, end);
 }
@@ -3718,6 +3720,8 @@ void btrfs_evict_inode(struct inode *inode)
 	unsigned long nr;
 	int ret;
 
+	trace_btrfs_inode_evict(inode);
+
 	truncate_inode_pages(&inode->i_data, 0);
 	if (inode->i_nlink && (btrfs_root_refs(&root->root_item) != 0 ||
 			       root == root->fs_info->tree_root))
@@ -4510,6 +4514,8 @@ static struct inode *btrfs_new_inode(struct btrfs_trans_handle *trans,
 		return ERR_PTR(-ENOMEM);
 
 	if (dir) {
+		trace_btrfs_inode_request(dir);
+
 		ret = btrfs_set_inode_index(dir, index);
 		if (ret) {
 			iput(inode);
@@ -4584,6 +4590,9 @@ static struct inode *btrfs_new_inode(struct btrfs_trans_handle *trans,
 
 	insert_inode_hash(inode);
 	inode_tree_add(inode);
+
+	trace_btrfs_inode_new(inode);
+
 	return inode;
 fail:
 	if (dir)
@@ -5261,6 +5270,9 @@ struct extent_map *btrfs_get_extent(struct inode *inode, struct page *page,
 	}
 	write_unlock(&em_tree->lock);
 out:
+
+	trace_btrfs_get_extent(root, em);
+
 	if (path)
 		btrfs_free_path(path);
 	if (trans) {

fs/btrfs/ordered-data.c

@@ -202,6 +202,8 @@ static int __btrfs_add_ordered_extent(struct inode *inode, u64 file_offset,
 	INIT_LIST_HEAD(&entry->list);
 	INIT_LIST_HEAD(&entry->root_extent_list);
 
+	trace_btrfs_ordered_extent_add(inode, entry);
+
 	spin_lock(&tree->lock);
 	node = tree_insert(&tree->tree, file_offset,
 			   &entry->rb_node);
@@ -387,6 +389,8 @@ int btrfs_put_ordered_extent(struct btrfs_ordered_extent *entry)
 	struct list_head *cur;
 	struct btrfs_ordered_sum *sum;
 
+	trace_btrfs_ordered_extent_put(entry->inode, entry);
+
 	if (atomic_dec_and_test(&entry->refs)) {
 		while (!list_empty(&entry->list)) {
 			cur = entry->list.next;
@@ -420,6 +424,8 @@ static int __btrfs_remove_ordered_extent(struct inode *inode,
 	spin_lock(&root->fs_info->ordered_extent_lock);
 	list_del_init(&entry->root_extent_list);
 
+	trace_btrfs_ordered_extent_remove(inode, entry);
+
 	/*
 	 * we have no more ordered extents for this inode and
 	 * no dirty pages.  We can safely remove it from the
@@ -585,6 +591,8 @@ void btrfs_start_ordered_extent(struct inode *inode,
 	u64 start = entry->file_offset;
 	u64 end = start + entry->len - 1;
 
+	trace_btrfs_ordered_extent_start(inode, entry);
+
 	/*
 	 * pages in the range can be dirty, clean or writeback.  We
 	 * start IO on any dirty ones so the wait doesn't stall waiting

fs/btrfs/super.c

@@ -52,6 +52,9 @@
 #include "export.h"
 #include "compression.h"
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/btrfs.h>
+
 static const struct super_operations btrfs_super_ops;
 
 static const char *btrfs_decode_error(struct btrfs_fs_info *fs_info, int errno,
@@ -620,6 +623,8 @@ int btrfs_sync_fs(struct super_block *sb, int wait)
 	struct btrfs_root *root = btrfs_sb(sb);
 	int ret;
 
+	trace_btrfs_sync_fs(wait);
+
 	if (!wait) {
 		filemap_flush(root->fs_info->btree_inode->i_mapping);
 		return 0;

fs/btrfs/transaction.c

@@ -1389,6 +1389,8 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
 	put_transaction(cur_trans);
 	put_transaction(cur_trans);
 
+	trace_btrfs_transaction_commit(root);
+
 	mutex_unlock(&root->fs_info->trans_mutex);
 
 	if (current->journal_info == trans)

fs/btrfs/volumes.c

@@ -33,17 +33,6 @@
 #include "volumes.h"
 #include "async-thread.h"
 
-struct map_lookup {
-	u64 type;
-	int io_align;
-	int io_width;
-	int stripe_len;
-	int sector_size;
-	int num_stripes;
-	int sub_stripes;
-	struct btrfs_bio_stripe stripes[];
-};
-
 static int init_first_rw_device(struct btrfs_trans_handle *trans,
 				struct btrfs_root *root,
 				struct btrfs_device *device);
@@ -1923,6 +1912,8 @@ static int btrfs_relocate_chunk(struct btrfs_root *root,
 
 	BUG_ON(ret);
 
+	trace_btrfs_chunk_free(root, map, chunk_offset, em->len);
+
 	if (map->type & BTRFS_BLOCK_GROUP_SYSTEM) {
 		ret = btrfs_del_sys_chunk(root, chunk_objectid, chunk_offset);
 		BUG_ON(ret);
@@ -2650,6 +2641,8 @@ static int __btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
 	*num_bytes = chunk_bytes_by_type(type, calc_size,
 					 map->num_stripes, sub_stripes);
 
+	trace_btrfs_chunk_alloc(info->chunk_root, map, start, *num_bytes);
+
 	em = alloc_extent_map(GFP_NOFS);
 	if (!em) {
 		ret = -ENOMEM;
@@ -2758,6 +2751,7 @@ static int __finish_chunk_alloc(struct btrfs_trans_handle *trans,
 					     item_size);
 		BUG_ON(ret);
 	}
+
 	kfree(chunk);
 	return 0;
 }

fs/btrfs/volumes.h

@@ -145,6 +145,17 @@ struct btrfs_device_info {
 	u64 max_avail;
 };
 
+struct map_lookup {
+	u64 type;
+	int io_align;
+	int io_width;
+	int stripe_len;
+	int sector_size;
+	int num_stripes;
+	int sub_stripes;
+	struct btrfs_bio_stripe stripes[];
+};
+
 /* Used to sort the devices by max_avail(descending sort) */
 int btrfs_cmp_device_free_bytes(const void *dev_info1, const void *dev_info2);