> Calling bdi_unregister() might be okay, and that should fix this. I'm > not familiar enough with that part to say for sure. > But freeing sb->s_bdi while the superblock is active looks problematic. Tracing the code, I see that, yes, in general that might not be safe to call the "bdi_put" function for any FS - because it might have in-flight ops even with force, where they will routinely access the members of the bdi struct without locks. However, we do replace the struct with a no_op version, and specifically for the FUSE case we sever the connection first, so no in-flight ops can actually be there. And I am not sure if other FS may need to do this retirement, given they don't have these user-space/kernel split. It would make sense however to delay the actual put till the actual super block destruction, but that would require introducing extra state tracking to see if the block is or is not registered anymore. It can be piggybacked on the v1 patch where I have an explicit state flag, but not on v2. Miklos, Al, will the following work and be acceptable? Get v1 patchset[1], in fuse_umount_begin do bdi_unregister and set the flag, but do not do bdi_put or replacement with no_op. And then in generic shutdown super if the bdi is not no_op and the 'defunct' flag is set, skip unregister part. Thanks, Daniil [1] https://lore.kernel.org/linux-fsdevel/20220511013057.245827-1-dlunev@xxxxxxxxxxxx/T/#u
