| Message ID | 20170421234026.18970-10-bart.vanassche@sandisk.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 04/22/2017 01:40 AM, Bart Van Assche wrote: > This new callback function will be used in the next patch to show > more information about SCSI requests. > > Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com> > Reviewed-by: Omar Sandoval <osandov@fb.com> > Cc: Hannes Reinecke <hare@suse.com> > --- > block/blk-mq-debugfs.c | 6 +++++- > include/linux/blk-mq.h | 6 ++++++ > 2 files changed, 11 insertions(+), 1 deletion(-) > > diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c > index 3a99146ece39..c5eca9245459 100644 > --- a/block/blk-mq-debugfs.c > +++ b/block/blk-mq-debugfs.c > @@ -311,6 +311,7 @@ static const char *const rqf_name[] = { > static int blk_mq_debugfs_rq_show(struct seq_file *m, void *v) > { > struct request *rq = list_entry_rq(v); > + const struct blk_mq_ops *const mq_ops = rq->q->mq_ops; > const unsigned int op = rq->cmd_flags & REQ_OP_MASK; > > seq_printf(m, "%p {.op=", rq); > @@ -324,8 +325,11 @@ static int blk_mq_debugfs_rq_show(struct seq_file *m, void *v) > seq_puts(m, ", .rq_flags="); > blk_flags_show(m, (__force unsigned int)rq->rq_flags, rqf_name, > ARRAY_SIZE(rqf_name)); > - seq_printf(m, ", .tag=%d, .internal_tag=%d}\n", rq->tag, > + seq_printf(m, ", .tag=%d, .internal_tag=%d", rq->tag, > rq->internal_tag); > + if (mq_ops->show_rq) > + mq_ops->show_rq(m, rq); > + seq_puts(m, "}\n"); > return 0; > } > > diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h > index 0c4dadb85f62..b7bf11c05568 100644 > --- a/include/linux/blk-mq.h > +++ b/include/linux/blk-mq.h > @@ -121,6 +121,12 @@ struct blk_mq_ops { > softirq_done_fn *complete; > > /* > + * Used by the debugfs implementation to show driver-specific > + * information about a request. > + */ > + void (*show_rq)(struct seq_file *m, struct request *rq); > + > + /* > * Called when the block layer side of a hardware queue has been > * set up, allowing the driver to allocate/init matching structures. > * Ditto for exit/teardown. > I don't really like this; what does happen if someone disabled CONFIG_BLK_DEBUGFS? Won't we end up with a stale callback? Cheers, Hannes
On Mon, 2017-04-24 at 09:32 +0200, Hannes Reinecke wrote: > On 04/22/2017 01:40 AM, Bart Van Assche wrote: > > --- a/include/linux/blk-mq.h > > +++ b/include/linux/blk-mq.h > > @@ -121,6 +121,12 @@ struct blk_mq_ops { > > softirq_done_fn *complete; > > > > /* > > + * Used by the debugfs implementation to show driver-specific > > + * information about a request. > > + */ > > + void (*show_rq)(struct seq_file *m, struct request *rq); > > + > > + /* > > * Called when the block layer side of a hardware queue has been > > * set up, allowing the driver to allocate/init matching structures. > > * Ditto for exit/teardown. > > > > I don't really like this; what does happen if someone disabled > CONFIG_BLK_DEBUGFS? Won't we end up with a stale callback? Hello Hannes, How about surrounding (*show_rq)() function pointer with #ifdef CONFIG_BLK_DEBUGFS / #endif? Bart.
On 04/24/2017 11:51 PM, Bart Van Assche wrote: > On Mon, 2017-04-24 at 09:32 +0200, Hannes Reinecke wrote: >> On 04/22/2017 01:40 AM, Bart Van Assche wrote: >>> --- a/include/linux/blk-mq.h >>> +++ b/include/linux/blk-mq.h >>> @@ -121,6 +121,12 @@ struct blk_mq_ops { >>> softirq_done_fn *complete; >>> >>> /* >>> + * Used by the debugfs implementation to show driver-specific >>> + * information about a request. >>> + */ >>> + void (*show_rq)(struct seq_file *m, struct request *rq); >>> + >>> + /* >>> * Called when the block layer side of a hardware queue has been >>> * set up, allowing the driver to allocate/init matching structures. >>> * Ditto for exit/teardown. >>> >> >> I don't really like this; what does happen if someone disabled >> CONFIG_BLK_DEBUGFS? Won't we end up with a stale callback? > > Hello Hannes, > > How about surrounding (*show_rq)() function pointer with #ifdef CONFIG_BLK_DEBUGFS / > #endif? > Nope. Then you'll end up with different offsets in the structures, depending on how the kernel is compiled. Making debugging a nightmare. Not sure what would be the best way here ... Cheers, Hannes
On Tue, 2017-04-25 at 17:16 +0200, Hannes Reinecke wrote: > On 04/24/2017 11:51 PM, Bart Van Assche wrote: > > On Mon, 2017-04-24 at 09:32 +0200, Hannes Reinecke wrote: > > > On 04/22/2017 01:40 AM, Bart Van Assche wrote: > > > > --- a/include/linux/blk-mq.h > > > > +++ b/include/linux/blk-mq.h > > > > @@ -121,6 +121,12 @@ struct blk_mq_ops { > > > > softirq_done_fn *complete; > > > > > > > > /* > > > > + * Used by the debugfs implementation to show driver-specific > > > > + * information about a request. > > > > + */ > > > > + void (*show_rq)(struct seq_file *m, struct request *rq); > > > > + > > > > + /* > > > > * Called when the block layer side of a hardware queue has been > > > > * set up, allowing the driver to allocate/init matching structures. > > > > * Ditto for exit/teardown. > > > > > > > > > > I don't really like this; what does happen if someone disabled > > > CONFIG_BLK_DEBUGFS? Won't we end up with a stale callback? > > > > How about surrounding (*show_rq)() function pointer with #ifdef CONFIG_BLK_DEBUGFS / > > #endif? > > Then you'll end up with different offsets in the structures, depending > on how the kernel is compiled. Making debugging a nightmare. Hello Hannes, How about moving the .show_rq function pointer to the end such that the offset of other members of struct blk_mq_ops does not depend on whether or not CONFIG_BLK_DEBUGFS has been defined? Bart.
On 04/25/2017 08:16 AM, Hannes Reinecke wrote: > On 04/24/2017 11:51 PM, Bart Van Assche wrote: >> On Mon, 2017-04-24 at 09:32 +0200, Hannes Reinecke wrote: >>> On 04/22/2017 01:40 AM, Bart Van Assche wrote: >>>> --- a/include/linux/blk-mq.h >>>> +++ b/include/linux/blk-mq.h >>>> @@ -121,6 +121,12 @@ struct blk_mq_ops { >>>> softirq_done_fn *complete; >>>> >>>> /* >>>> + * Used by the debugfs implementation to show driver-specific >>>> + * information about a request. >>>> + */ >>>> + void (*show_rq)(struct seq_file *m, struct request *rq); >>>> + >>>> + /* >>>> * Called when the block layer side of a hardware queue has been >>>> * set up, allowing the driver to allocate/init matching structures. >>>> * Ditto for exit/teardown. >>>> >>> >>> I don't really like this; what does happen if someone disabled >>> CONFIG_BLK_DEBUGFS? Won't we end up with a stale callback? >> >> Hello Hannes, >> >> How about surrounding (*show_rq)() function pointer with #ifdef CONFIG_BLK_DEBUGFS / >> #endif? >> > Nope. > > Then you'll end up with different offsets in the structures, depending > on how the kernel is compiled. Making debugging a nightmare. That's nonsense, we deal with this all the time already.
diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c index 3a99146ece39..c5eca9245459 100644 --- a/block/blk-mq-debugfs.c +++ b/block/blk-mq-debugfs.c @@ -311,6 +311,7 @@ static const char *const rqf_name[] = { static int blk_mq_debugfs_rq_show(struct seq_file *m, void *v) { struct request *rq = list_entry_rq(v); + const struct blk_mq_ops *const mq_ops = rq->q->mq_ops; const unsigned int op = rq->cmd_flags & REQ_OP_MASK; seq_printf(m, "%p {.op=", rq); @@ -324,8 +325,11 @@ static int blk_mq_debugfs_rq_show(struct seq_file *m, void *v) seq_puts(m, ", .rq_flags="); blk_flags_show(m, (__force unsigned int)rq->rq_flags, rqf_name, ARRAY_SIZE(rqf_name)); - seq_printf(m, ", .tag=%d, .internal_tag=%d}\n", rq->tag, + seq_printf(m, ", .tag=%d, .internal_tag=%d", rq->tag, rq->internal_tag); + if (mq_ops->show_rq) + mq_ops->show_rq(m, rq); + seq_puts(m, "}\n"); return 0; } diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h index 0c4dadb85f62..b7bf11c05568 100644 --- a/include/linux/blk-mq.h +++ b/include/linux/blk-mq.h @@ -121,6 +121,12 @@ struct blk_mq_ops { softirq_done_fn *complete; /* + * Used by the debugfs implementation to show driver-specific + * information about a request. + */ + void (*show_rq)(struct seq_file *m, struct request *rq); + + /* * Called when the block layer side of a hardware queue has been * set up, allowing the driver to allocate/init matching structures. * Ditto for exit/teardown.