On Mon, Feb 12, 2024 at 08:09:26AM +0000, Al Viro wrote: > Bloody bad idea, IMO. Note that straight use of kill_anon_super() > pretty much forces you into doing everything from ->put_super(). > And that leads to rather clumsy failure exits in foo_fill_super(), > since you *won't* get ->put_super() called unless you've got to > setting ->s_root. > > Considering how easily the failure exits rot, I'd rather discourage > that variant. BTW, take a look at fs/ext2/super.c and compare the mess in failure exits in ext2_fill_super() with ext2_put_super(). See the amount of duplication? In case of ext2_fill_super() success eventual ->kill_sb() will call ->put_super() (from generic_shutdown_super(), from kill_block_super()). What happens in case of ext2_fill_super() failure? ->kill_sb() is called, but ->put_super() is only called if ->s_root is non-NULL (and at the very least it requires ->s_op to have been set). So in that case we have ext2_fill_super() manually undo the allocations, etc. it had managed to do, same as ext2_put_super() would've done. If that stuff gets lifted into ->kill_sb(), we get the bulk of ext2_put_super() moved into ext2_kill_super() (I wouldn't be surprised if ext2_put_super() completely disappeared, actually), with all those goto failed_mount<something> in ext2_fill_super() turning into plain return -E...
