On Fri, Sep 23, 2022 at 02:15:05PM +0800, ZiyangZhang wrote: > Add documentation for user recovery feature of ublk subsystem. > > Signed-off-by: ZiyangZhang <ZiyangZhang@xxxxxxxxxxxxxxxxx> > --- > Documentation/block/ublk.rst | 32 ++++++++++++++++++++++++++++++++ > 1 file changed, 32 insertions(+) > > diff --git a/Documentation/block/ublk.rst b/Documentation/block/ublk.rst > index 2122d1a4a541..c3dde087e601 100644 > --- a/Documentation/block/ublk.rst > +++ b/Documentation/block/ublk.rst > @@ -144,6 +144,38 @@ managing and controlling ublk devices with help of several control commands: > For retrieving device info via ``ublksrv_ctrl_dev_info``. It is the server's > responsibility to save IO target specific info in userspace. > > +- ``UBLK_CMD_START_USER_RECOVERY`` > + > + This command is valid if ``UBLK_F_USER_RECOVERY`` feature is enabled. This > + command is accepted after the old process has exited, ublk device is quiesced > + and ``/dev/ublkc*`` is closed. User should send this command before he starts > + a new process which opens ``/dev/ublkc*``. When this command returns, the > + ublk device is ready for the new process. > + > +- ``UBLK_CMD_END_USER_RECOVERY`` > + > + This command is valid if ``UBLK_F_USER_RECOVERY`` feature is enabled. This > + command is accepted after a new process has opened ``/dev/ublkc*`` and get > + all ublk queues be ready. When this command returns, ublk device is > + unquiesced and new I/O requests are passed to the new process. > + > +- user recovery feature description > + > + Two new features are added for user recovery: ``UBLK_F_USER_RECOVERY`` and > + ``UBLK_F_USER_RECOVERY_REISSUE``. > + > + With ``UBLK_F_USER_RECOVERY`` set, after one ubq_daemon(ublksrv io handler) is > + dying, ublk does not release ``/dev/ublkc*`` or ``/dev/ublkb*`` but requeues all The above looks not accurate, the old ubq daemon has to release /dev/ublkc*, and the new ubq daemon needs to re-open it, and here I think it is fine to just mention /dev/ublkb* won't be deleted during the whole recovery, or the device ID is kept, and it is ublk server's responsibility to recover the device context by its own knowledge. thanks, Ming
