Re: [PATCH v2 2/2] mm/swapfile: release swap info when swap device is unpluged

[Christoph Hellwig]

Sorry, but this is simply broken.  We can't just do d_path magic
here.  That being said the problem is real, and I think the right
answer is to offer a swapoff variant that doesn't need to open the
underlying device or file, but useѕ some kind of handle.  I'm just
not sure what would be a good handle here.