On Fri, Jul 04, 2025 at 10:12:29AM +0930, Qu Wenruo wrote: > Currently all the filesystems implementing the > super_opearations::shutdown() callback 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, with multi-device filesystems like > btrfs and bcachefs the filesystem can handle certain device loss without > shutting down the whole filesystem. > > To allow those multi-device filesystems to be integrated to use > fs_holder_ops: > > - Replace super_opearation::shutdown() with > super_opearations::remove_bdev() > To better describe when the callback is called.
This conflates cause with action. The shutdown callout is an action that the filesystem must execute, whilst "remove bdev" is a cause notification that might require an action to be take. Yes, the cause could be someone doing hot-unplug of the block device, but it could also be something going wrong in software layers below the filesystem. e.g. dm-thinp having an unrecoverable corruption or ENOSPC errors. We already have a "cause" notification: blk_holder_ops->mark_dead(). The generic fs action that is taken by this notification is fs_bdev_mark_dead(). That action is to invalidate caches and shut down the filesystem. btrfs needs to do something different to a blk_holder_ops->mark_dead notification. i.e. it needs an action that is different to fs_bdev_mark_dead(). Indeed, this is how bcachefs already handles "single device died" events for multi-device filesystems - see bch2_fs_bdev_mark_dead(). Hence Btrfs should be doing the same thing as bcachefs. The bdev_handle_ops structure exists precisly because it allows the filesystem to handle block device events in the exact manner they require.... > - Add a new @bdev parameter to remove_bdev() callback > To allow the fs to determine which device is missing, and do the > proper handling when needed. > > For the existing shutdown callback users, the change is minimal. Except for the change in API semantics. ->shutdown is an external shutdown trigger for the filesystem, not a generic "block device removed" notification. Hooking blk_holder_ops->mark_dead means that btrfs can also provide a ->shutdown implementation for when something external other than a block device removal needs to shut down the filesystem.... -Dave. -- Dave Chinner da...@fromorbit.com _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
