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Commit 0aefa054 authored by Vishal Verma's avatar Vishal Verma Committed by Dan Williams
Browse files

libnvdimm, btt: update the usage section in Documentation 



Section 5 about BTT's in kernel usage was quite obsolete,
replace it with a simple 'Usage' section that describes how
to set up a BTT namespace using the 'ndctl' utility.

Signed-off-by: default avatarVishal Verma <vishal.l.verma@intel.com>
Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
parent f02716db

Documentation/nvdimm/btt.txt

+9 −19
Original line number Diff line number Diff line
@@ -256,28 +256,18 @@ If any of these error conditions are encountered, the arena is put into a read 
only state using a flag in the info block.





5. In-kernel usage

==================

5. Usage

========



Any block driver that supports byte granularity IO to the storage may register

with the BTT. It will have to provide the rw_bytes interface in its

block_device_operations struct:

The BTT can be set up on any disk (namespace) exposed by the libnvdimm subsystem

(pmem, or blk mode). The easiest way to set up such a namespace is using the

'ndctl' utility [1]:



	int (*rw_bytes)(struct gendisk *, void *, size_t, off_t, int rw);

For example, the ndctl command line to setup a btt with a 4k sector size is:



It may register with the BTT after it adds its own gendisk, using btt_init:

    ndctl create-namespace -f -e namespace0.0 -m sector -l 4k



	struct btt *btt_init(struct gendisk *disk, unsigned long long rawsize,

			u32 lbasize, u8 uuid[], int maxlane);

See ndctl create-namespace --help for more options.



note that maxlane is the maximum amount of concurrency the driver wishes to

allow the BTT to use.



The BTT 'disk' appears as a stacked block device that grabs the underlying block

device in the O_EXCL mode.



When the driver wishes to remove the backing disk, it should similarly call

btt_fini using the same struct btt* handle that was provided to it by btt_init.



	void btt_fini(struct btt *btt);

[1]: https://github.com/pmem/ndctl