nvmet: expose reservation state through debugfs

Add a 'reservation' debugfs file under each namespace directory that
shows the persistent reservation state, including enable status,
generation counter, notify mask, current holder info, and the full
registrant list with hostid and reservation key.

Each attribute is emitted as a single "key=value" line so the output is
easy to parse from scripts. The registrant list is emitted as repeated
"reg=" lines. The notify mask is emitted as a comma-separated list of
masked notification names. Empty values are reported as "none". Example
output:

    enable=1
    generation=2
    notify_mask=reg_preempted,resv_released,resv_preempted
    rtype=write_exclusive
    holder=11111111-1111-1111-1111-111111111111,0x1111
    reg=11111111-1111-1111-1111-111111111111,0x1111
    reg=22222222-2222-2222-2222-222222222222,0x2222

When reservation is not enabled only "enable=0" is printed.

The output uses rcu_read_lock() for safe access to the holder and
registrant_list, consistent with other PR read paths.

Reviewed-by: Daniel Wagner <dwagner@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Guixin Liu <kanie@linux.alibaba.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>

0 files changed, 0 insertions, 0 deletions