linux-kernel - [PATCH 0/7] blk_holder

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Message-ID: <20250307134933.1033872-1-kent.overstreet@linux.dev>
Date: Fri,  7 Mar 2025 08:49:24 -0500
From: Kent Overstreet <kent.overstreet@...ux.dev>
To: linux-bcachefs@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: Kent Overstreet <kent.overstreet@...ux.dev>
Subject: [PATCH 0/7] blk_holder_ops, freeze/thaw

Until now, it turns out bcachefs has been lacking freeze/thaw support,
which is important for hibernate.

We thought we had freeze/thaw support, but it turns out that when
.freeze_fs and .unfreeze_fs were implemented in super_operations, they
were never being called - those functions are only called from the
blk_holder callbacks, and the engineer implementing them never thought
to check that.

So - there's a lesson here, and this is why I keep harping on testing.
It's not enough to just fire off the automated test suite and call it a
day, you do have to put actual thought into checking that your code is
behaving as expected :)

It turns out the method we were originally talking about for freeze/thaw
of just using our existing read-only/read-write paths doesn't work, for
reasons that I neglected to remember when hooking up blk_holder_ops
(locking and conflicting state management, I assume), so we need to
block IOs at a lower level - which conveniently we can do with our
existing per-device IO references.

This patchset also implements the other blk holder ops - the big one
being mark_dead, which now offlines a single device from the filesystem
if possible (leaving the filesystem read-write), or if not possible to
run in degraded mode, sets the entire filesystem read only.

Kent Overstreet (7):
  fs: export invalidate_inodes()
  bcachefs: Stash a pointer to the filesystem for blk_holder_ops
  bcachefs: Make sure c->vfs_sb is set before starting fs
  bcachefs: Implement blk_holder_ops
  bcachefs: Fix btree_node_scan io_ref handling
  bcachefs: bch2_dev_get_ioref() may now sleep
  bcachefs: Implement freeze/thaw

 fs/bcachefs/bcachefs.h        |   3 +
 fs/bcachefs/btree_node_scan.c |  17 ++-
 fs/bcachefs/fs.c              |  11 +-
 fs/bcachefs/journal_io.c      |   7 +-
 fs/bcachefs/sb-members.c      |  49 +++++++++
 fs/bcachefs/sb-members.h      |  18 +---
 fs/bcachefs/super-io.c        |   5 +-
 fs/bcachefs/super.c           | 191 +++++++++++++++++++++++++++++++++-
 fs/bcachefs/super.h           |   2 +
 fs/bcachefs/super_types.h     |   8 +-
 fs/inode.c                    |   1 +
 fs/internal.h                 |   1 -
 include/linux/fs.h            |   1 +
 13 files changed, 272 insertions(+), 42 deletions(-)

-- 
2.47.2