slab warning: kmem_cache of name 'dm_bufio_buffer' already exists

[Mikulas Patocka <mpatocka@redhat.com>]

Hi

The commit 4c39529663b93165953ecf9b1a9ea817358dcd06 ("slab: Warn on 
duplicate cache names when DEBUG_VM=y") is causing large number of 
warnings about "dm_bufio_buffer", "dm_bufio_buffer-%u" (and other) device 
mapper caches.

I'd like to ask - how to properly fix it?

We create a "dm_bufio_buffer" or "dm_bufio_buffer-%u" cache with every dm 
bufio client. It used to work (and the duplicate caches are merged), but 
now it warns.

Should I append a pointer to the dm_bufio structure to the slab cache name 
to make them different? Or is there any other preferred solution?

Note that it is not possible to pre-create the cache "dm_bufio_buffer-%u" 
in the module's init function, because the size of per-buffer auxiliary 
data is not known at this point.

Mikulas