Messages in this thread | | | Subject | Re: [PATCH 0/4] Remove un-needed 'major' registration when alloc_disk(0) is used. | From | Jens Axboe <> | Date | Tue, 15 Mar 2016 17:20:15 -0700 |
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On 03/15/2016 03:15 PM, NeilBrown wrote: > On Tue, Mar 15 2016, Ross Zwisler wrote: > >> 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 >>> driver. >>> >>> Note that I am not in a position to test these beyond simple compile >>> testing. >>> >>> Thanks, >>> NeilBrown >>> >>> >>> --- >>> >>> 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. > > null_blk looks like it would be safe to convert - it is just used for > testing. Jens Axboe would probably know for sure. > > virtio_blk is a much older and there may will be code which has some > sort of expectations about minor numbers. I think it would not be worth > the risks to change it.
Agree on both - null_blk can be trivially converted, and I too would be worried about virt_blkio changes breaking existing assumptions.
-- Jens Axboe
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