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START_USER_RECOVERY and END_USER_RECOVERY are two new control commands
to support user recovery feature.
After a crash, user should send START_USER_RECOVERY, it will:
(1) check if (a)current ublk_device is UBLK_S_DEV_QUIESCED which was
set by quiesce_work and (b)chardev is released
(2) reinit all ubqs, including:
(a) put the task_struct and reset ->ubq_daemon to NULL.
(b) reset all ublk_io.
(3) reset ub->mm to NULL.
Then, user should start a new process and send FETCH_REQ on each
ubq_daemon.
Finally, user should send END_USER_RECOVERY, it will:
(1) wait for all new ubq_daemons getting ready.
(2) update ublksrv_pid
(3) unquiesce the request queue and expect incoming ublk_queue_rq()
(4) convert ub's state to UBLK_S_DEV_LIVE
Note: we can handle STOP_DEV between START_USER_RECOVERY and
END_USER_RECOVERY. This is helpful to users who cannot start new process
after sending START_USER_RECOVERY ctrl-cmd.
Signed-off-by: ZiyangZhang <ZiyangZhang@linux.alibaba.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20220923153919.44078-7-ZiyangZhang@linux.alibaba.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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UBLK_F_USER_RECOVERY_REISSUE implies that:
With a dying ubq_daemon, ublk_drv let monitor_work requeues rq issued to
userspace(ublksrv) before the ubq_daemon is dying.
UBLK_F_USER_RECOVERY_REISSUE is designed for backends which:
(1) tolerate double-write since ublk_drv may issue the same rq
twice.
(2) does not let frontend users get I/O error, such as read-only FS
and VM backend.
Signed-off-by: ZiyangZhang <ZiyangZhang@linux.alibaba.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20220923153919.44078-6-ZiyangZhang@linux.alibaba.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Define some macros for recovery feature.
UBLK_S_DEV_QUIESCED implies that ublk_device is quiesced
and is ready for recovery. This state can be observed by userspace.
UBLK_F_USER_RECOVERY implies that:
(1) ublk_drv enables recovery feature. It won't let monitor_work to
automatically abort rqs and release the device.
(2) With a dying ubq_daemon, ublk_drv ends(aborts) rqs issued to
userspace(ublksrv) before crash.
(3) With a dying ubq_daemon, in task work and ublk_queue_rq(),
ublk_drv requeues rqs.
Signed-off-by: ZiyangZhang <ZiyangZhang@linux.alibaba.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20220923153919.44078-3-ZiyangZhang@linux.alibaba.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Add one new ublk command: UBLK_IO_NEED_GET_DATA. It is prepared for a new
feature designed for a user application who wants to allocate IO buffer
and set IO buffer address only after it receives an IO request from
ublksrv.
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: ZiyangZhang <ZiyangZhang@linux.alibaba.com>
Link: https://lore.kernel.org/r/c8a64b6b51c78340da7daa9e1054608695e79619.1659011443.git.ZiyangZhang@linux.alibaba.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Remove all block device related info from ublksrv_ctrl_dev_info,
meantime reduce its size into 64 bytes because:
1) ublksrv_ctrl_dev_info becomes cleaner without including any
block related info
2) generic set/get parameter command can be used to set block
related setting easily and cleanly
3) generic set/get parameter command can be used for extending
ublk without needing more info in ublksrv_ctrl_dev_info
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20220730092750.1118167-5-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Add two commands to set/get parameters generically.
One important goal of ublk is to provide generic framework for making
block device by userspace flexibly.
As one generic block device, there are still lots of block parameters,
such as max_sectors, write_cache/fua, discard related limits,
zoned parameters, ...., so this patch starts to add generic mechanism
for set/get device parameters.
Both generic block parameters(all kinds of queue settings) and ublk
feature parameters can be covered with this way, then it becomes quite
easy to extend in future.
Add two parameter types are used so far: basic(covers basic queue setting
and misc settings which can't be grouped easily) and discard, basic type
must be set, and discard type becomes optional now
This way provides mechanism to simulate any kind of generic block device
from userspace easily, from both block queue setting viewpoint or ublk
feature viewpoint.
The style of putting all parameters together is suggested by Christoph.
Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20220730092750.1118167-4-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Userspace may support more features or new added flags, but the driver
side can be old, so make sure correct flags(features) returned to
userpsace, then userspace can work as expected.
Also mark the 2nd flags as reversed, just use the 1st one. When we run
out of flags, the reserved one can be handled at that time.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: ZiyangZhang <ZiyangZhang@linux.alibaba.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20220722103817.631258-3-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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REQ_PREFLUSH is turned into REQ_OP_FLUSH by the flush state machine
and thus never seen by a blk-mq based driver.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20220721130916.1869719-3-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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The ublk protocol has no mechanism to actually transfer the integrity
metadata, so don't define this flag, which requires that an integrity
payload is attached to a bio.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220718063013.335531-1-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Use task_work_add if it is available, since task_work_add can bring
up better performance, especially batching signaling ->ubq_daemon can
be done.
It is observed that task_work_add() can boost iops by +4% on random
4k io test. Also except for completing io command, all other code
paths are same with completing io command via
io_uring_cmd_complete_in_task.
Meantime add one flag of UBLK_F_URING_CMD_COMP_IN_TASK for comparing
the mode easily.
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20220713140711.97356-3-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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This is the driver part of userspace block driver(ublk driver), the other
part is userspace daemon part(ublksrv)[1].
The two parts communicate by io_uring's IORING_OP_URING_CMD with one
shared cmd buffer for storing io command, and the buffer is read only for
ublksrv, each io command is indexed by io request tag directly, and is
written by ublk driver.
For example, when one READ io request is submitted to ublk block driver,
ublk driver stores the io command into cmd buffer first, then completes
one IORING_OP_URING_CMD for notifying ublksrv, and the URING_CMD is issued
to ublk driver beforehand by ublksrv for getting notification of any new
io request, and each URING_CMD is associated with one io request by tag.
After ublksrv gets the io command, it translates and handles the ublk io
request, such as, for the ublk-loop target, ublksrv translates the request
into same request on another file or disk, like the kernel loop block
driver. In ublksrv's implementation, the io is still handled by io_uring,
and share same ring with IORING_OP_URING_CMD command. When the target io
request is done, the same IORING_OP_URING_CMD is issued to ublk driver for
both committing io request result and getting future notification of new
io request.
Another thing done by ublk driver is to copy data between kernel io
request and ublksrv's io buffer:
1) before ubsrv handles WRITE request, copy the request's data into
ublksrv's userspace io buffer, so that ublksrv can handle the write
request
2) after ubsrv handles READ request, copy ublksrv's userspace io buffer
into this READ request, then ublk driver can complete the READ request
Zero copy may be switched if mm is ready to support it.
ublk driver doesn't handle any logic of the specific user space driver,
so it is small/simple enough.
[1] ublksrv
https://github.com/ming1/ubdsrv
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20220713140711.97356-2-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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