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nvmet: support fabrics sq flow control

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Technical proposal 8005 "fabrics SQ flow control" introduces a mode
where a host and controller agree to omit sq_head pointer updates
when sending nvme completions.

In case the host indicated desire to operate in this mode (connect attribute)
the controller will return back a connect completion with sq_head value
of 0xffff as indication that it will omit sq_head pointer updates.

This mode saves us an atomic update in the I/O path.

Reviewed-by: Hannes Reinecke <hare@suse.com>
[hch: suggested better implementation]
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Sagi Grimberg
2018-11-19 14:11:12 -08:00
committed by Jens Axboe
parent 6e2e312ea7
commit e6a622fd6d
4 changed files with 24 additions and 10 deletions
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4
include/linux/nvme.h
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@@ -1044,6 +1044,10 @@ struct nvmf_disc_rsp_page_hdr {
struct nvmf_disc_rsp_page_entry entries[0];
};
enum {
NVME_CONNECT_DISABLE_SQFLOW = (1 << 2),
};
struct nvmf_connect_command {
__u8 opcode;
__u8 resv1;