Commit ad5f2e29 authored by Caleb Sander Mateos's avatar Caleb Sander Mateos Committed by Jens Axboe
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ublk: restore auto buf unregister refcount optimization 



Commit 1ceeedb5 ("ublk: optimize UBLK_IO_UNREGISTER_IO_BUF on daemon
task") optimized ublk request buffer unregistration to use a non-atomic
reference count decrement when performed on the ublk_io's daemon task.
The optimization applied to auto buffer unregistration, which happens as
part of handling UBLK_IO_COMMIT_AND_FETCH_REQ on the daemon task.
However, commit b749965e ("ublk: remove ublk_commit_and_fetch()")
reordered the ublk_sub_req_ref() for the completed request before the
io_buffer_unregister_bvec() call. As a result, task_registered_buffers
is already 0 when io_buffer_unregister_bvec() calls ublk_io_release()
and the non-atomic refcount optimization doesn't apply.
Move the io_buffer_unregister_bvec() call back to before
ublk_need_complete_req() to restore the reference counting optimization.

Signed-off-by: default avatarCaleb Sander Mateos <csander@purestorage.com>
Fixes: b749965e ("ublk: remove ublk_commit_and_fetch()")
Reviewed-by: default avatarMing Lei <ming.lei@redhat.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 2719bd1e

drivers/block/ublk_drv.c

+2 −2
Original line number Diff line number Diff line
@@ -3334,11 +3334,11 @@ static int ublk_ch_uring_cmd_local(struct io_uring_cmd *cmd, 
		io->res = result;

		req = ublk_fill_io_cmd(io, cmd);

		ret = ublk_config_io_buf(ub, io, cmd, addr, &buf_idx);

		if (buf_idx != UBLK_INVALID_BUF_IDX)

			io_buffer_unregister_bvec(cmd, buf_idx, issue_flags);

		compl = ublk_need_complete_req(ub, io);



		/* can't touch 'ublk_io' any more */

		if (buf_idx != UBLK_INVALID_BUF_IDX)

			io_buffer_unregister_bvec(cmd, buf_idx, issue_flags);

		if (req_op(req) == REQ_OP_ZONE_APPEND)

			req->__sector = addr;

		if (compl)