linux-ext4 - [PATCH v2 0/3] jbd2/ext4/ocfs2: lockless jinode dirty range

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Message-ID: <20260219114645.778338-1-me@linux.beauty>
Date: Thu, 19 Feb 2026 19:46:41 +0800
From: Li Chen <me@...ux.beauty>
To: Theodore Ts'o <tytso@....edu>,
	Jan Kara <jack@...e.cz>,
	Mark Fasheh <mark@...heh.com>,
	linux-ext4@...r.kernel.org,
	ocfs2-devel@...ts.linux.dev,
	Matthew Wilcox <willy@...radead.org>
Cc: Andreas Dilger <adilger.kernel@...ger.ca>,
	Joel Becker <jlbec@...lplan.org>,
	Joseph Qi <joseph.qi@...ux.alibaba.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2 0/3] jbd2/ext4/ocfs2: lockless jinode dirty range

This series makes the jbd2_inode dirty range tracking safe for lockless
reads in jbd2 and filesystem callbacks used by ext4 and ocfs2.

Some paths access jinode fields without holding journal->j_list_lock
(e.g. fast commit helpers and ordered truncate helpers). v1 used READ_ONCE()
on i_dirty_start/end, but Matthew pointed out that loff_t can be torn on
32-bit platforms, and Jan suggested storing the dirty range in PAGE_SIZE
units as pgoff_t.

With this series, jbd2 stores i_dirty_start/end as pgoff_t and uses
READ_ONCE()/WRITE_ONCE() for lockless access. ext4 and ocfs2 convert the
page-based dirty range back to byte offsets for writeback.

This is based on Jan's suggestion in the review of the ext4 jinode
publication race fix. [1]

Changes since v1:
- Store i_dirty_start/end in PAGE_SIZE units (pgoff_t) to avoid torn loads on
  32-bit (pointed out by Matthew, suggested by Jan).
- Use WRITE_ONCE() for i_dirty_* / i_flags updates in jbd2 (per Jan).
- Drop pointless READ_ONCE() on i_vfs_inode in jbd2_wait_inode_data (per Jan).
- Convert ext4/ocfs2 callbacks to translate page range to byte offsets.

[1]: https://lore.kernel.org/all/4jxwogttddiaoqbstlgou5ox6zs27ngjjz5ukrxafm2z5ijxod@so4eqnykiegj/

v1: https://lore.kernel.org/all/20260130031232.60780-1-me@linux.beauty/

Li Chen (3):
  jbd2: store jinode dirty range in PAGE_SIZE units
  ext4: use READ_ONCE for lockless jinode reads
  ocfs2: use READ_ONCE for lockless jinode reads

 fs/ext4/inode.c       | 12 ++++++--
 fs/ext4/super.c       | 19 +++++++++----
 fs/jbd2/commit.c      | 65 ++++++++++++++++++++++++++++++++++---------
 fs/jbd2/journal.c     |  3 +-
 fs/jbd2/transaction.c | 20 ++++++++-----
 fs/ocfs2/journal.c    | 13 +++++++--
 include/linux/jbd2.h  | 17 +++++++----
 7 files changed, 113 insertions(+), 36 deletions(-)

-- 
2.52.0