linux-kernel - [GIT PULL 13/14 for v6.17] vfs super

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Message-ID: <20250725-vfs-super-5977952856e4@brauner>
Date: Fri, 25 Jul 2025 13:27:27 +0200
From: Christian Brauner <brauner@...nel.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Christian Brauner <brauner@...nel.org>,
	linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [GIT PULL 13/14 for v6.17] vfs super

Hey Linus,

/* Summary */
Currently all filesystems which implement super_operations::shutdown()
can not afford losing a device.

Thus fs_bdev_mark_dead() will just call the ->shutdown() callback for the
involved filesystem.

But it will no longer be the case, as multi-device filesystems like
btrfs can handle certain device loss without the need to shutdown the
whole filesystem.

To allow those multi-device filesystems to be integrated to use
fs_holder_ops:

- Add a new super_operations::remove_bdev() callback

- Try ->remove_bdev() callback first inside fs_bdev_mark_dead()
  If the callback returned 0, meaning the fs can handling the device
  loss, then exit without doing anything else.

  If there is no such callback or the callback returned non-zero value,
  continue to shutdown the filesystem as usual.

This means the new remove_bdev() should only do the check on whether the
operation can continue, and if so do the fs specific handlings. The
shutdown handling should still be handled by the existing ->shutdown()
callback.

For all existing filesystems with shutdown callback, there is no change
to the code nor behavior.

Btrfs is going to implement both the ->remove_bdev() and ->shutdown()
callbacks soon.

/* Testing */

gcc (Debian 14.2.0-19) 14.2.0
Debian clang version 19.1.7 (3)

No build failures or warnings were observed.

/* Conflicts */

Merge conflicts with mainline
=============================

No known conflicts.

Merge conflicts with other trees
================================

No known conflicts.

The following changes since commit 19272b37aa4f83ca52bdf9c16d5d81bdd1354494:

  Linux 6.16-rc1 (2025-06-08 13:44:43 -0700)

are available in the Git repository at:

  git@...olite.kernel.org:pub/scm/linux/kernel/git/vfs/vfs tags/vfs-6.17-rc1.super

for you to fetch changes up to d9c37a4904ec21ef7d45880fe023c11341869c28:

  fs: add a new remove_bdev() callback (2025-07-15 13:36:40 +0200)

Please consider pulling these changes from the signed vfs-6.17-rc1.super tag.

Thanks!
Christian

----------------------------------------------------------------
vfs-6.17-rc1.super

----------------------------------------------------------------
Qu Wenruo (1):
      fs: add a new remove_bdev() callback

 fs/super.c         | 11 +++++++++++
 include/linux/fs.h |  9 +++++++++
 2 files changed, 20 insertions(+)