| Date | Thu, 31 May 2018 20:19:55 +0100 | From | Al Viro <> | Subject | Re: [PATCH 20/32] vfs: Make close() unmount the attached mount if so flagged [ver #8] |
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On Fri, May 25, 2018 at 01:07:34AM +0100, David Howells wrote: > + if (unlikely(file->f_mode & FMODE_NEED_UNMOUNT)) > + __detach_mounts(dentry); > +
This is completely wrong. First of all, you want to dissolve the mount tree on file->f_path.mount, not every tree rooted at dentry equal to file->f_path.dentry. This is easily done - it would be a simple call of drop_collected_mounts(mnt) if not for one detail. You want it to happen only if the sucker isn't attached anywhere by that point. IOW, namespace_lock(); lock_mount_hash(); if (!real_mount(mnt)->mnt_ns) umount_tree(real_mount(mnt), UMOUNT_SYNC); unlock_mount_hash(); namespace_unlock(); and that's it. You don't need that magical mystery turd in move_mount() later in the series and all the infrastructure you grow for it.
FWIW, I would've suggested this void drop_collected_mounts(struct vfsmount *mnt) { namespace_lock(); lock_mount_hash(); + if (!real_mount(mnt)->mnt_ns) + umount_tree(real_mount(mnt), UMOUNT_SYNC); - umount_tree(real_mount(mnt), UMOUNT_SYNC); unlock_mount_hash(); namespace_unlock(); }
and in __fput() if (unlikely(file->f_mode & FMODE_NEED_UNMOUNT)) drop_collected_mounts(mnt);
All there is to it, AFAICS...
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