On Mon, 24 Jan 2022 12:54:01 -0800
Yang Shi <shy828301@xxxxxxxxx> wrote:
> Hi folks,
>
> I think the problems fixed by this patch still exist and we do need
> this patch to make disk error handling in rasdaemon easier. I saw
> Steven already gave his reviewed-by, I'm wondering why this patch was
> not merged to upstream? I didn't see any unsolved comments.
Maybe I did that prematurely, as I think I found a mistake in the tracing
below.
>
> If it looks fine, would Jens (I guess it should go with block tree)
> please merge this patch upstream? The latest kernel moved
> blk_update_request() to blk-mq.c, if it is ok to move forward, I could
> prepare a new version.
>
> Thanks,
> Yang
>
> On Sun, Feb 2, 2020 at 11:15 PM Cong Wang <xiyou.wangcong@xxxxxxxxx> 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@xxxxxxxxx>
> > Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
> > Signed-off-by: Cong Wang <xiyou.wangcong@xxxxxxxxx>
> > ---
> > block/blk-core.c | 4 +++-
> > include/trace/events/block.h | 41 ++++++++++++++++++++++++++++++++++++
> > 2 files changed, 44 insertions(+), 1 deletion(-)
> >
> > diff --git a/block/blk-core.c b/block/blk-core.c
> > index 089e890ab208..0c7ad70d06be 100644
> > --- a/block/blk-core.c
> > +++ b/block/blk-core.c
> > @@ -1450,8 +1450,10 @@ 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);
> > print_req_error(req, error, __func__);
> > + }
> >
> > blk_account_io_completion(req, nr_bytes);
> >
> > diff --git a/include/trace/events/block.h b/include/trace/events/block.h
> > index 81b43f5bdf23..575054e7cfa0 100644
> > --- a/include/trace/events/block.h
> > +++ b/include/trace/events/block.h
> > @@ -145,6 +145,47 @@ TRACE_EVENT(block_rq_complete,
> > __entry->nr_sector, __entry->error)
> > );
> >
> > +/**
> > + * block_rq_error - block IO operation error reported by device driver
> > + * @rq: block operations request
> > + * @error: status code
> > + * @nr_bytes: number of completed bytes
> > + *
> > + * The block_rq_error tracepoint event indicates that some portion
> > + * of operation request has failed as reported by the device driver.
> > + */
> > +TRACE_EVENT(block_rq_error,
> > +
> > + TP_PROTO(struct request *rq, int error, unsigned int nr_bytes),
> > +
> > + TP_ARGS(rq, error, nr_bytes),
> > +
> > + TP_STRUCT__entry(
> > + __field( dev_t, dev )
> > + __string( name, rq->rq_disk ? rq->rq_disk->disk_name : "?")
> > + __field( sector_t, sector )
> > + __field( unsigned int, nr_sector )
> > + __field( int, error )
> > + __array( char, rwbs, RWBS_LEN )
Why is the above not "__string" ?
> > + ),
> > +
> > + TP_fast_assign(
> > + __entry->dev = rq->rq_disk ? disk_devt(rq->rq_disk) : 0;
> > + __assign_str(name, rq->rq_disk ? rq->rq_disk->disk_name : "?");
__assign_str() will not work on an __array() type. It only works here
because you added it at the end, but it's just shear luck that it didn't
crash.
-- Steve
> > + __entry->sector = blk_rq_pos(rq);
> > + __entry->nr_sector = nr_bytes >> 9;
> > + __entry->error = error;
> > +
> > + blk_fill_rwbs(__entry->rwbs, rq->cmd_flags, nr_bytes);
> > + ),
> > +
> > + TP_printk("%d,%d %s %s %llu + %u [%d]",
> > + MAJOR(__entry->dev), MINOR(__entry->dev),
> > + __get_str(name), __entry->rwbs,
> > + (unsigned long long)__entry->sector,
> > + __entry->nr_sector, __entry->error)
> > +);
> > +
> > DECLARE_EVENT_CLASS(block_rq,
> >
> > TP_PROTO(struct request_queue *q, struct request *rq),
> > --
> > 2.21.1
> >
