linux-kernel - [PATCH v4 0/4] Remove the XFS mrlock

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Date:   Fri, 17 Nov 2023 14:51:38 +0000
From:   "Matthew Wilcox (Oracle)" <willy@...radead.org>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
        Waiman Long <longman@...hat.com>
Cc:     "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Chandan Babu R <chandan.babu@...cle.com>,
        "Darrick J . Wong" <djwong@...nel.org>, linux-xfs@...r.kernel.org,
        Mateusz Guzik <mjguzik@...il.com>
Subject: [PATCH v4 0/4] Remove the XFS mrlock

XFS has an mrlock wrapper around the rwsem which adds only the
functionality of knowing whether the rwsem is currently held in read
or write mode.  Both regular rwsems and rt-rwsems know this, they just
don't expose it as an API.  By adding that, we can remove the XFS mrlock
as well as improving the debug assertions for the mmap_lock when lockdep
is disabled.

v4:
 - Switch the BUG_ONs to WARN_ONs (Wayman, Peter)

v3:
 - Rename __rwsem_assert_held() and __rwsem_assert_held_write() to
   rwsem_assert_held*_nolockdep()
 - Use IS_ENABLED(CONFIG_LOCKDEP) to only dump the information once
 - Use ASSERT instead of BUG_ON in xfs
 - Fix typo in subject line of patch 4
 - Drop patch 5 (inode_assert_locked)
 - Rebase on top of xfs-6.7-merge-2 which had a merge conflict

v2: Add rwsem_assert_held() and rwsem_assert_held_write() instead of
augmenting the existing rwsem_is_locked() with rwsem_is_write_locked().
There's also an __rwsem_assert_held() and __rwsem_assert_held_write()
for the benefit of XFS when it's in a context where lockdep doesn't
know what's going on.  It's still an improvement, so I hope those who
are looking for perfection can accept a mere improvement.

We can do more to replace uses of rwsem_is_locked(), and I have a few of
those in my tree, but let's focus on these two use cases for now and
we can trickle in other improvements through other maintainers after 6.8.


Matthew Wilcox (Oracle) (4):
  locking: Add rwsem_assert_held() and rwsem_assert_held_write()
  mm: Use rwsem assertion macros for mmap_lock
  xfs: Replace xfs_isilocked with xfs_assert_ilocked
  xfs: Remove mrlock wrapper

 fs/xfs/libxfs/xfs_attr.c        |  2 +-
 fs/xfs/libxfs/xfs_attr_remote.c |  2 +-
 fs/xfs/libxfs/xfs_bmap.c        | 19 ++++----
 fs/xfs/libxfs/xfs_defer.c       |  2 +-
 fs/xfs/libxfs/xfs_inode_fork.c  |  2 +-
 fs/xfs/libxfs/xfs_rtbitmap.c    |  2 +-
 fs/xfs/libxfs/xfs_trans_inode.c |  6 +--
 fs/xfs/mrlock.h                 | 78 ------------------------------
 fs/xfs/scrub/readdir.c          |  4 +-
 fs/xfs/xfs_attr_list.c          |  2 +-
 fs/xfs/xfs_bmap_util.c          | 10 ++--
 fs/xfs/xfs_dir2_readdir.c       |  2 +-
 fs/xfs/xfs_dquot.c              |  4 +-
 fs/xfs/xfs_file.c               |  4 +-
 fs/xfs/xfs_inode.c              | 86 ++++++++++++---------------------
 fs/xfs/xfs_inode.h              |  4 +-
 fs/xfs/xfs_inode_item.c         |  4 +-
 fs/xfs/xfs_iops.c               |  7 ++-
 fs/xfs/xfs_linux.h              |  2 +-
 fs/xfs/xfs_qm.c                 | 10 ++--
 fs/xfs/xfs_reflink.c            |  2 +-
 fs/xfs/xfs_rtalloc.c            |  4 +-
 fs/xfs/xfs_super.c              |  4 +-
 fs/xfs/xfs_symlink.c            |  2 +-
 fs/xfs/xfs_trans_dquot.c        |  2 +-
 include/linux/mmap_lock.h       | 10 ++--
 include/linux/rwbase_rt.h       |  9 +++-
 include/linux/rwsem.h           | 46 ++++++++++++++++--
 28 files changed, 132 insertions(+), 199 deletions(-)
 delete mode 100644 fs/xfs/mrlock.h

-- 
2.42.0