linux-kernel - [PATCH 0/3] enumarated refcounts, for debugging refcount issues

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Message-ID: <20250420155918.749455-1-kent.overstreet@linux.dev>
Date: Sun, 20 Apr 2025 11:59:13 -0400
From: Kent Overstreet <kent.overstreet@...ux.dev>
To: linux-bcachefs@...r.kernel.org,
	linux-fsdevel@...r.kernel.org,
	linux-hardening@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: Kent Overstreet <kent.overstreet@...ux.dev>
Subject: [PATCH 0/3] enumarated refcounts, for debugging refcount issues

Not sure we have a list for library code, but this might be of interest
to anyone who's had to debug refcount issues on refs with lots of users
(filesystem people), and I know the hardening folks deal with refcounts
a lot.

In release mode, this is just a wrapper around percpu refcounts.

In debug mode, this provides separate sub-refcounts for each enumerated
user, and provides facilities for printing them.

Meaning, if you're debugging a refcount issue, you no longer have to go
searching through the entire codebase - it'll tell you the exact
codepath.

bcachefs patches are provided as example usage, for other subsystems.

Kent Overstreet (3):
  bcachefs: enumerated_ref.c
  bcachefs: bch_fs.writes -> enumerated_refs
  bcachefs: bch_dev.io_ref -> enumerated_ref

 fs/bcachefs/Makefile                |   1 +
 fs/bcachefs/alloc_background.c      |  41 ++++----
 fs/bcachefs/backpointers.c          |   6 +-
 fs/bcachefs/bcachefs.h              | 105 ++++++++++----------
 fs/bcachefs/btree_gc.c              |   7 +-
 fs/bcachefs/btree_io.c              |  29 +++---
 fs/bcachefs/btree_node_scan.c       |  10 +-
 fs/bcachefs/btree_trans_commit.c    |   5 +-
 fs/bcachefs/btree_update_interior.c |   7 +-
 fs/bcachefs/btree_write_buffer.c    |  11 ++-
 fs/bcachefs/buckets.c               |   4 +-
 fs/bcachefs/debug.c                 |  12 ++-
 fs/bcachefs/ec.c                    |  32 ++++---
 fs/bcachefs/enumerated_ref.c        | 144 ++++++++++++++++++++++++++++
 fs/bcachefs/enumerated_ref.h        |  66 +++++++++++++
 fs/bcachefs/enumerated_ref_types.h  |  19 ++++
 fs/bcachefs/fs-io-direct.c          |   7 +-
 fs/bcachefs/fs-io.c                 |  15 +--
 fs/bcachefs/io_read.c               |  17 ++--
 fs/bcachefs/io_write.c              |  20 ++--
 fs/bcachefs/journal.c               |  10 +-
 fs/bcachefs/journal_io.c            |  15 +--
 fs/bcachefs/journal_reclaim.c       |   2 +-
 fs/bcachefs/reflink.c               |   5 +-
 fs/bcachefs/sb-members.h            |  32 ++++---
 fs/bcachefs/snapshot.c              |   7 +-
 fs/bcachefs/subvolume.c             |   7 +-
 fs/bcachefs/super-io.c              |  18 ++--
 fs/bcachefs/super.c                 | 125 +++++++++++-------------
 fs/bcachefs/super.h                 |   3 +
 fs/bcachefs/sysfs.c                 |  46 ++++-----
 31 files changed, 540 insertions(+), 288 deletions(-)
 create mode 100644 fs/bcachefs/enumerated_ref.c
 create mode 100644 fs/bcachefs/enumerated_ref.h
 create mode 100644 fs/bcachefs/enumerated_ref_types.h

-- 
2.49.0