[PATCH 0/2] Reduce scope of extent locking while reading

[Goldwyn Rodrigues <rgoldwyn@suse.de>]

From: Goldwyn Rodrigues <rgoldwyn@suse.com>

Extent locking is not required for the entire read process. Once the
extent map is read all information to retrieve is available in the
extent map, and is cached in em_cached for later retrieval. The extent
map cached is also refcounted so it would not disappear.
Limit the extent locking while reading the extnet maps only. The rest is
just creating bio and fetching/decompressing the data according to the
extent map provided.

The only reason this was not working is because we would get EIO as
the CRCs would not match (or were not committed to disk as yet) for
folios that were written and released. In order to get over it, mark the
extent as finished only after all folios are cleared of writeback.

I have run the xfstests on it without any deadlocks or corruptions.
However, a fresh outlook on what could go wrong with a limiting the
scope of locks would be good.

Goldwyn Rodrigues (2):
  btrfs: clear folio writeback after completing ordered range
  btrfs: take extent lock only while reading extent map

 fs/btrfs/compression.c |  5 ---
 fs/btrfs/extent_io.c   | 99 +++---------------------------------------
 2 files changed, 7 insertions(+), 97 deletions(-)

-- 
2.46.0