| From bb023a788fb3ded53d7a6207e6b9075f0ff68f09 Mon Sep 17 00:00:00 2001 |
| From: Sasha Levin <sashal@kernel.org> |
| Date: Wed, 28 Jan 2026 13:56:34 -0700 |
| Subject: ublk: restore auto buf unregister refcount optimization |
| |
| From: Caleb Sander Mateos <csander@purestorage.com> |
| |
| [ Upstream commit ad5f2e2908c9b79a86529281a48e94d644d43dc7 ] |
| |
| Commit 1ceeedb59749 ("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 b749965edda8 ("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: Caleb Sander Mateos <csander@purestorage.com> |
| Fixes: b749965edda8 ("ublk: remove ublk_commit_and_fetch()") |
| Reviewed-by: Ming Lei <ming.lei@redhat.com> |
| Signed-off-by: Jens Axboe <axboe@kernel.dk> |
| Signed-off-by: Sasha Levin <sashal@kernel.org> |
| --- |
| drivers/block/ublk_drv.c | 4 ++-- |
| 1 file changed, 2 insertions(+), 2 deletions(-) |
| |
| diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c |
| index 4b6d7b785d7b3..56058090d223e 100644 |
| --- a/drivers/block/ublk_drv.c |
| +++ b/drivers/block/ublk_drv.c |
| @@ -2526,11 +2526,11 @@ 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) |
| -- |
| 2.51.0 |
| |
