On Mon, May 7, 2018 at 10:43 AM, Dongsheng Yang
<dongsheng.yang@xxxxxxxxxxxx> wrote:
> We need to know the rbd options for a rbd device, such as whether lock_on_read
> is true or false. then this patch introduce a rbd_options to show the rbd options in sysfs.
I'm not convinced this is really needed. Once something is added to
sysfs it is there to stay, and your solution only works for per mapping
options (and not for per client, i.e. libceph) options. We don't have
a good place for libceph options -- ideally it would be a per libceph
instance directory (doesn't exist), linked to from per rbd instance
directories (exist) and per ceph instance directories (doesn't exist).
Getting those pieces that don't exist right and taking it through
review is a significant effort and hasn't been high on the list.
/sys/bus/rbd/devices/<id>/config_info shows an entire string written
into sysfs by "rbd map". All options supplied to "rbd map" (including
libceph options) are part of that string, so if you need to recall an
option that was supplied to "rbd map", look at config_info.
It doesn't list defaults, but they are documented in the man page.
We haven't changed a single default in the past few years, so there
shouldn't be any confusion there. Take lock_on_read as an example:
if grep -q lock_on_read /sys/bus/rbd/devices/0/config_info; then
echo "lock_on_read: true"
else
echo "lock_on_read: false (default)"
fi
Thanks,
Ilya
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