slab: Warn on duplicate cache names when DEBUG_VM=y

slab: Warn on duplicate cache names when DEBUG_VM=y

Duplicate slab cache names can create havoc for userspace tooling that
expects slab cache names to be unique [1]. This is a reasonable
expectation.

Sadly, too many duplicate name problems are out there in the wild, so
simply warn instead of pr_err() + failing the sanity check.

[ [email protected]: change to WARN_ON(), see the discussion at [2] ]

Link: https://lore.kernel.org/linux-fsdevel/2d1d053da1cafb3e7940c4f25952da4f0af34e38.1722293276.git.osandov@fb.com/
Link: https://lore.kernel.org/all/[email protected]/
Signed-off-by: Pedro Falcato <[email protected]>
Acked-by: Christoph Lameter <[email protected]>
Signed-off-by: Vlastimil Babka <[email protected]>