[PATCH 0/5] Assertion and debugging helpers

[David Sterba <dsterba@suse.com>]

Hi,

this is a RFC series. We need to improve debugging and logging helpers
so there's no ASSERT(0) or the convoluted
WARN_ON(IS_DEFINED(CONFIG_BTRFS_DEBUG)). This was mentioned in past
discussions so here's my proposal.

The series is only build tested, I'd like to hear some feedback if this
is going the right direction or if there are suggestions for fine
tuning.

1) Add verbose ASSERT macro, so we can print additional information when
it triggers, namely printing the values of the assertion expression.
More details in the first patch, basic pattern is something like

    VASSERT(value > limit, "value=%llu limit=%llu", value, limit);

The second patch shows it's application in volumes.c, converting about
half where it's relevant. There are about 800 assertions in fs/btrfs/
and we don't need to convert them all. This can be done incrementally
and as needed.

The verbose version is another macro, although with some preprocessor
magic it should be possible to make ASSERT take variable number of
arguments. Does not seem worth though.

2) Wrap WARN_ON(IS_DEFINED(CONFIG_BTRFS_DEBUG)) to DEBUG_WARN() with
optional message with printk format. This is used to replace the
WARN_ON(...) above and also the ASSERT(0).

The ultimate goal for me is to get rid of all ASSERT(0), it's not used
consistently and looks like it's a note to the code author. There may be
several reasons for it's use and although I've converted almost all to
DEBUG_WARN it may miss the intentions.

In some cases it may be better to add proper error handling, print a
message or warn and exit with error. Possibly the are cases where the
code cannot continue, meaning it should be a BUG_ON but this is also
something we want to convert to proper error handling.

David Sterba (5):
  btrfs: add verbose version of ASSERT
  btrfs: example use of VASSERT() in volumes.c
  btrfs: add debug build only WARN
  btrfs: convert WARN_ON(IS_ENABLED(CONFIG_BTRFS_DEBUG)) to DEBUG_WARN
  btrfs: convert ASSERT(0) to DEBUG_WARN()

 fs/btrfs/backref.c         |  4 +--
 fs/btrfs/delayed-ref.c     |  2 +-
 fs/btrfs/dev-replace.c     |  2 +-
 fs/btrfs/disk-io.c         |  2 +-
 fs/btrfs/extent-tree.c     |  2 +-
 fs/btrfs/extent_io.c       |  4 +--
 fs/btrfs/extent_map.c      |  2 +-
 fs/btrfs/free-space-tree.c | 27 +++++++++-------
 fs/btrfs/inode.c           |  6 ++--
 fs/btrfs/messages.h        | 30 ++++++++++++++++++
 fs/btrfs/qgroup.c          |  6 ++--
 fs/btrfs/relocation.c      |  4 +--
 fs/btrfs/send.c            |  4 +--
 fs/btrfs/space-info.c      |  2 +-
 fs/btrfs/tree-checker.c    |  8 ++---
 fs/btrfs/volumes.c         | 64 ++++++++++++++++++++++++--------------
 fs/btrfs/zoned.c           |  2 +-
 17 files changed, 109 insertions(+), 62 deletions(-)

-- 
2.49.0