5edfd9fdc6
Modify btrfs_qgroup_account_extent() to exit quicker for non-fs extents.
The quick exit condition is:
1) The extent belongs to a non-fs tree
Only fs-tree extents can affect qgroup numbers and is the only case
where extent can be shared between different trees.
Although strictly speaking extent in data-reloc or tree-reloc tree
can be shared, data/tree-reloc root won't appear in the result of
btrfs_find_all_roots(), so we can ignore such case.
So we can check the first root in old_roots/new_roots ulist.
- if we find the 1st root is a not a fs/subvol root, then we can skip
the extent
- if we find the 1st root is a fs/subvol root, then we must continue
calculation
OR
2) both 'nr_old_roots' and 'nr_new_roots' are 0
This means either such extent got allocated then freed in current
transaction or it's a new reloc tree extent, whose nr_new_roots is 0.
Either way it won't affect qgroup accounting and can be skipped
safely.
Such quick exit can make trace output more quite and less confusing:
(example with fs uuid and time stamp removed)
Before:
------
add_delayed_tree_ref: bytenr=29556736 num_bytes=16384 action=ADD_DELAYED_REF parent=0(-) ref_root=2(EXTENT_TREE) level=0 type=TREE_BLOCK_REF seq=0
btrfs_qgroup_account_extent: bytenr=29556736 num_bytes=16384 nr_old_roots=0 nr_new_roots=1
------
Extent tree block will trigger btrfs_qgroup_account_extent() trace point
while no qgroup number is changed, as extent tree won't affect qgroup
accounting.
After:
------
add_delayed_tree_ref: bytenr=29556736 num_bytes=16384 action=ADD_DELAYED_REF parent=0(-) ref_root=2(EXTENT_TREE) level=0 type=TREE_BLOCK_REF seq=0
------
Now such unrelated extent won't trigger btrfs_qgroup_account_extent()
trace point, making the trace less noisy.
Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
[ changelog and comment adjustments ]
Signed-off-by: David Sterba <dsterba@suse.com>
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README
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.