Commit 1abe9b8a authored Mar 24, 2011 by liubo Committed by root Mar 28, 2011

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>

parent 240f62c8

fs/btrfs/ctree.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -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

+1 −0

Original line number	Diff line number	Diff line
		@@ -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

+6 −0

Original line number	Diff line number	Diff line
		@@ -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

+4 −0

Original line number	Diff line number	Diff line
		@@ -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

+2 −0

Original line number	Diff line number	Diff line
		@@ -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 \|\|