On Tue, Jul 30, 2024 at 06:09:27AM +0100, Al Viro wrote: > * ib_uverbs_open_xrcd(). FWIW, a closer look shows that the > damn thing is buggy - it accepts _any_ descriptor and pins the associated > inode. mount tmpfs, open a file there, feed it to that, unmount and > watch the show... What happens? There is still an igrab() while it is in the red black tree? > AFAICS, that's done for the sake of libibverbs and > I've no idea how it's actually used - all examples I'd been able to > find use -1 for descriptor here. Needs to be discussed with infiniband > folks (Sean Hefty?). For now, leave that as-is. The design seems insane, but it is what it is from 20 years ago.. Userspace can affiliate this "xrc domain" with a file in the filesystem. Any file. That is actually a deliberate part of the API. This is done as some ugly way to pass xrc domain object from process A to process B. IIRC the idea is process A will affiliate the object with a file and then B will be able to access the shared object if B is able to open the file. It looks like the code keeps a red/black tree of this association, and holds an igrab while the inode is in that tree.. Jason
