Re: [PATCH 0/4] Remove un-needed 'major' registration when alloc_disk(0) is used.
From: Ross Zwisler
Date: Mon Mar 14 2016 - 18:50:45 EST
On Thu, Mar 10, 2016 at 08:59:28AM +1100, NeilBrown wrote:
> When alloc_disk(0) is used, the ->major number is ignored and
> irrelevant. Yet several drivers register a major number anyway.
> This series of patches removes the pointless registrations. The pmem
> driver also does this, but a patch has already been sent for that
> Note that I am not in a position to test these beyond simple compile
> NeilBrown (4):
> nvdimm/blk: don't allocate unused major device number
> nvdimm/btt: don't allocate unused major device number
> memstick: don't allocate unused major for ms_block
> NVMe: don't allocate unused nvme_major
> drivers/memstick/core/ms_block.c | 17 ++---------------
> drivers/nvdimm/blk.c | 18 +-----------------
> drivers/nvdimm/btt.c | 19 ++-----------------
> drivers/nvme/host/core.c | 16 +---------------
> 4 files changed, 6 insertions(+), 64 deletions(-)
There are several other drivers that allocate a major, but then use it for
some small number of minors (1 for null_blk.c and 16 for virtio_blk.c). They
both have GENHD_FL_EXT_DEVT set, so I think what happens is that after we
exhaust the allocated minors they hop over to having BLOCK_EXT_MAJOR as a
major and a dynamically assigned minor.
It seems like these could easily be converted in the same way so they'd use
BLOCK_EXT_MAJOR for their major and have a bunch of dynamically assigned
Does this break something I'm not seeing?
Yay for this series, by the way. :)