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SubjectRe: [v4 PATCH] block: introduce block_rq_error tracepoint
On Tue, Jan 25, 2022 at 12:35:48PM -0800, Yang Shi wrote:
> Currently, rasdaemon uses the existing tracepoint block_rq_complete
> and filters out non-error cases in order to capture block disk errors.
>
> But there are a few problems with this approach:
>
> 1. Even kernel trace filter could do the filtering work, there is
> still some overhead after we enable this tracepoint.
>
> 2. The filter is merely based on errno, which does not align with kernel
> logic to check the errors for print_req_error().
>
> 3. block_rq_complete only provides dev major and minor to identify
> the block device, it is not convenient to use in user-space.
>
> So introduce a new tracepoint block_rq_error just for the error case
> and provides the device name for convenience too. With this patch,
> rasdaemon could switch to block_rq_error.
>
> Cc: Jens Axboe <axboe@kernel.dk>
> Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
> Signed-off-by: Yang Shi <shy828301@gmail.com>
> ---
> The v3 patch was submitted in Feb 2020, and Steven reviewed the patch, but
> it was not merged to upstream. See
> https://lore.kernel.org/lkml/20200203053650.8923-1-xiyou.wangcong@gmail.com/.
>
> The problems fixed by that patch still exist and we do need it to make
> disk error handling in rasdaemon easier. So this resurrected it and
> continued the version number.
>
> v3 --> v4:
> * Rebased to v5.17-rc1.
> * Collected reviewed-by tag from Steven.
>
> block/blk-mq.c | 4 +++-
> include/trace/events/block.h | 41 ++++++++++++++++++++++++++++++++++++
> 2 files changed, 44 insertions(+), 1 deletion(-)
>
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index f3bf3358a3bb..bb0593f93675 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -789,8 +789,10 @@ bool blk_update_request(struct request *req, blk_status_t error,
> #endif
>
> if (unlikely(error && !blk_rq_is_passthrough(req) &&
> - !(req->rq_flags & RQF_QUIET)))
> + !(req->rq_flags & RQF_QUIET))) {
> + trace_block_rq_error(req, blk_status_to_errno(error), nr_bytes);

Please report the atual block layer status code instead of the errno
mapping here.

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