btrfs: tracepoints: Add trace events for extent_io_tree
Although btrfs heavily relies on extent_io_tree, we don't really have
any good trace events for them.
This patch will add the folowing trace events:
- trace_btrfs_set_extent_bit()
- trace_btrfs_clear_extent_bit()
- trace_btrfs_convert_extent_bit()
Since selftests could create temporary extent_io_tree without fs_info,
modify TP_fast_assign_fsid() to accept NULL as fs_info. NULL fs_info
will lead to all zero fsid.
The output would be:
btrfs_set_extent_bit: <FDID>: io_tree=INODE_IO ino=1 root=1 start=
22036480 len=4096 set_bits=LOCKED
btrfs_set_extent_bit: <FSID>: io_tree=INODE_IO ino=1 root=1 start=
22040576 len=4096 set_bits=LOCKED
btrfs_set_extent_bit: <FSID>: io_tree=INODE_IO ino=1 root=1 start=
22044672 len=4096 set_bits=LOCKED
btrfs_set_extent_bit: <FSID>: io_tree=INODE_IO ino=1 root=1 start=
22048768 len=4096 set_bits=LOCKED
btrfs_clear_extent_bit: <FSID>: io_tree=INODE_IO ino=1 root=1 start=
22036480 len=16384 clear_bits=LOCKED
^^^ Extent buffer
22036480 read from disk, the locking progress
btrfs_set_extent_bit: <FSID>: io_tree=TRANS_DIRTY_PAGES ino=1 root=1 start=
30425088 len=16384 set_bits=DIRTY
btrfs_set_extent_bit: <FSID>: io_tree=TRANS_DIRTY_PAGES ino=1 root=1 start=
30441472 len=16384 set_bits=DIRTY
^^^ 2 new tree blocks allocated in one transaction
btrfs_set_extent_bit: <FSID>: io_tree=FREED_EXTENTS0 ino=0 root=0 start=
30523392 len=16384 set_bits=DIRTY
btrfs_set_extent_bit: <FSID>: io_tree=FREED_EXTENTS0 ino=0 root=0 start=
30556160 len=16384 set_bits=DIRTY
^^^ 2 old tree blocks get pinned down
There is one point which need attention:
1) Those trace events can be pretty heavy:
The following workload would generate over 400 trace events.
mkfs.btrfs -f $dev
start_trace
mount $dev $mnt -o enospc_debug
sync
touch $mnt/file1
touch $mnt/file2
touch $mnt/file3
xfs_io -f -c "pwrite 0 16k" $mnt/file4
umount $mnt
end_trace
It's not recommended to use them in real world environment.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ rename enums ]
Signed-off-by: David Sterba <dsterba@suse.com>