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@xxxxxxxxxxxxxxxxxxx: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(+)
