[PATCH 0/4] Fix incorrect splitting logic in btrfs_drop_extent_map_range

[Josef Bacik <josef@toxicpanda.com>]

We have been hitting a fair number of warnings in btrfs_drop_extent_map_range
and in unpin_extent_map in production.  Upon investigation I discovered we were
splitting improperly when we call btrfs_drop_extent_map_range with skip_pinned.
This results in invalid extent_maps in the inode's io_tree, which in turn wreaks
all sorts of havoc, mostly in the form of these WARN_ON()'s.  This took me a
while to spot so I have a bunch of self-tests that test various functionality of
btrfs_drop_extent_map_range and btrfs_add_extent_mapping, with one test that
actual exercises the bug.

This has been broken for a while, and thankfully is only triggered in certain
cases with relocation on.  Our environment uses auto relocation heavily which is
why we hit this reliably, but the incident rate is still relatively low.  The
bug was introduced over 10 years ago, it probably could be limited to being
backported to the most recent kernels, basically anytime after Filipe's cleaning
up of this code.  Thanks,

Josef

Josef Bacik (4):
  btrfs: fix incorrect splitting in btrfs_drop_extent_map_range
  btrfs: add extent_map tests for dropping with odd layouts
  btrfs: add a self test for btrfs_add_extent_mapping
  btrfs: test invalid splitting when skipping pinned drop extent_map

 fs/btrfs/extent_map.c             |   6 +-
 fs/btrfs/tests/extent-map-tests.c | 414 ++++++++++++++++++++++++++++++
 2 files changed, 416 insertions(+), 4 deletions(-)

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2.26.3