[PATCH 0/1] Documentation: document ublk user recovery

[PATCH 0/1] Documentation: document ublk user recovery

[ZiyangZhang]

User recovery feature of ublk has been merged. Add documentation for
it.

ZiyangZhang (1):
  Documentation: document ublk user recovery feature

 Documentation/block/ublk.rst | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)


base-commit: 76dd298094f484c6250ebd076fa53287477b2328
-- 
2.27.0

[PATCH 1/1] Documentation: document ublk user recovery feature

[ZiyangZhang]

Add documentation for user recovery feature of ublk subsystem.

Signed-off-by: ZiyangZhang <ZiyangZhang@linux.alibaba.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
---
 Documentation/block/ublk.rst | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/Documentation/block/ublk.rst b/Documentation/block/ublk.rst
index 2122d1a4a541..ba45c46cc0da 100644
--- a/Documentation/block/ublk.rst
+++ b/Documentation/block/ublk.rst
@@ -144,6 +144,42 @@ 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 released. User should send this command before he starts
+  a new process which re-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 ublk device is quiesced and 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(ublk server's io
+  handler) is dying, ublk does not delete ``/dev/ublkb*`` during the whole
+  recovery stage and ublk device ID is kept. It is ublk server's
+  responsibility to recover the device context by its own knowledge.
+  Requests which have not been issued to userspace are requeued. Requests
+  which have been issued to userspace are aborted.
+
+  With ``UBLK_F_USER_RECOVERY_REISSUE`` set, after one ubq_daemon(ublk
+  server's io handler) is dying, contrary to ``UBLK_F_USER_RECOVERY``,
+  requests which have been issued to userspace are requeued and will be
+  re-issued to the new process after handling ``UBLK_CMD_END_USER_RECOVERY``.
+  ``UBLK_F_USER_RECOVERY_REISSUE`` is designed for backends who tolerate
+  double-write since the driver may issue the same I/O request twice. It
+  might be useful to a read-only FS or a VM backend.
+
 Data plane
 ----------
 
-- 
2.27.0

Re: [PATCH 0/1] Documentation: document ublk user recovery

[Ziyang Zhang]

Hi Jens,

This doc patch is resent since user recovery feature of ublk has been merged. 
Please consider it.

Regards,
Zhang.

Re: [PATCH 0/1] Documentation: document ublk user recovery

[Jens Axboe]

On Tue, 18 Oct 2022 12:53:45 +0800, ZiyangZhang wrote:
> User recovery feature of ublk has been merged. Add documentation for
> it.
> 
> ZiyangZhang (1):
>   Documentation: document ublk user recovery feature
> 
>  Documentation/block/ublk.rst | 36 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 36 insertions(+)
> 
> [...]

Applied, thanks!

[1/1] Documentation: document ublk user recovery feature
      commit: e0539ae012ba5d618eb19665ff990b87b960c643

Best regards,
-- 
Jens Axboe