[PATCH v4 0/4] btrfs: Refactor find_free_extent()

[Qu Wenruo <wqu@suse.com>]

Can be fetched from github:
https://github.com/adam900710/linux/tree/refactor_find_free_extent

Which is based on v4.19-rc1.

extent-tree.c::find_free_extent() could be one of the most
ill-structured functions, it has at least 6 non-exit tags and jumps
between them.

Refactor it into 4 parts:

1) find_free_extent()
   The main entrance, does the main work of block group iteration and
   block group selection.
   Now this function doesn't care nor handles free extent search by
   itself.

2) find_free_extent_clustered()
   Do clustered free extent search.
   May try to build/re-fill cluster.

3) find_free_extent_unclustered()
   Do unclustered free extent search.
   May try to fill free space cache.

4) find_free_extent_update_loop()
   Do the loop based black magic.
   May allocate new chunk.

With this patch, at least we should make find_free_extent() a little
easier to read, and provides the basis for later work on this function.

Current refactor is trying not to touch the original functionality, thus
the helper structure find_free_extent_ctl still contains a lot of
unrelated members.
But it should not change how find_free_extent() works at all.

changelog:
v2:
  Split into 4 patches.
  Minor comment newline change.
v3:
  Mostly cosmetic update.
  Rebased to v4.19-rc1
  Rename find_free_extent_ctrl to find_free_extent_ctl to keep the
  naming scheme the same.
  Fix some comment spelling error.
  Enhance comment for find_free_extent_unclustered().
  Add reviewed-by tag.
v4:
  Move the (ins->objectid) check to proper location of the last patch,
  so all (!ins->objectid) branches are in the same code block.
  Add reviewed-by tags from Josef.

Qu Wenruo (4):
  btrfs: Introduce find_free_extent_ctl structure for later rework
  btrfs: Refactor clustered extent allocation into
    find_free_extent_clustered()
  btrfs: Refactor unclustered extent allocation into
    find_free_extent_unclustered()
  btrfs: Refactor find_free_extent() loops update into
    find_free_extent_update_loop()

 fs/btrfs/extent-tree.c | 704 ++++++++++++++++++++++++-----------------
 1 file changed, 406 insertions(+), 298 deletions(-)

-- 
2.19.1