[PATCH] block: add calls to split trace point

[PATCH] block: add calls to split trace point

[Mike Krinkin]

There is a split tracepoint that is supposed to be called before
splitting a bio, and it was actually called in bio_split function
until commit 4b1faf931650d4a35b2a ("block: Kill bio_pair_split()").
But now, no one reports splits, so this patch adds calls to
trace_block_split back right before bio_split.

Signed-off-by: Mike Krinkin <krinkin.m.u@gmail.com>
---
 block/blk-merge.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/block/blk-merge.c b/block/blk-merge.c
index de5716d8..832ec49 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -7,6 +7,8 @@
 #include <linux/blkdev.h>
 #include <linux/scatterlist.h>
 
+#include <trace/events/block.h>
+
 #include "blk.h"
 
 static struct bio *blk_bio_discard_split(struct request_queue *q,
@@ -49,6 +51,7 @@ static struct bio *blk_bio_discard_split(struct request_queue *q,
 	if (split_sectors > tmp)
 		split_sectors -= tmp;
 
+	trace_block_split(q, bio, bio->bi_iter.bi_sector + split_sectors);
 	return bio_split(bio, split_sectors, GFP_NOIO, bs);
 }
 
@@ -65,6 +68,7 @@ static struct bio *blk_bio_write_same_split(struct request_queue *q,
 	if (bio_sectors(bio) <= q->limits.max_write_same_sectors)
 		return NULL;
 
+	trace_block_split(q, bio, bio->bi_iter.bi_sector);
 	return bio_split(bio, q->limits.max_write_same_sectors, GFP_NOIO, bs);
 }
 
@@ -117,6 +121,7 @@ new_segment:
 	return NULL;
 split:
 	*segs = nsegs;
+	trace_block_split(q, bio, bio->bi_iter.bi_sector + sectors);
 	return bio_split(bio, sectors, GFP_NOIO, bs);
 }
 
-- 
1.9.1

Re: [PATCH] block: add calls to split trace point

[Christoph Hellwig]

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH] block: add calls to split trace point

[Mike Krinkin]

Hi Jens,

i would like to check status of the patch, will the patch be applied?

Re: [PATCH] block: add calls to split trace point

[Jens Axboe]

On 12/02/2015 01:25 AM, Mike Krinkin wrote:
> Hi Jens,
>
> i would like to check status of the patch, will the patch be applied?
>

Why aren't you just putting the split trace call into blk_queue_split()?

-- 
Jens Axboe

Re: [PATCH] block: add calls to split trace point

[Mike Krinkin]

On Wed, Dec 02, 2015 at 10:06:09AM -0700, Jens Axboe wrote:
> On 12/02/2015 01:25 AM, Mike Krinkin wrote:
> >Hi Jens,
> >
> >i would like to check status of the patch, will the patch be applied?
> >
> 
> Why aren't you just putting the split trace call into blk_queue_split()?

Do you mean after split? Something like this:

	if (split) {
		/* there isn't chance to merge the splitted bio */
		split->bi_rw |= REQ_NOMERGE;

		bio_chain(split, *bio);
		trace_block_split(q, split, bio->bi_iter.bi_sector);
		generic_make_request(*bio);
		*bio = split;
	}

block_split trace event docs says that it expects "bio being split", i
understood it as "bio before split". But scarcely someone depends on
this behaviour, so i'll resend the patch, is it ok?

[PATCH] block: add call to split trace point

[Mike Krinkin]

There is a split tracepoint that is supposed to be called when
bio is splitted, and it was called in bio_split function until
commit 4b1faf931650d4a35b2a ("block: Kill bio_pair_split()").
But now, no one reports splits, so this patch adds call to
trace_block_split back in blk_queue_split right after split.

Signed-off-by: Mike Krinkin <krinkin.m.u@gmail.com>
---
 block/blk-merge.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/block/blk-merge.c b/block/blk-merge.c
index de5716d8..3bb4537 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -7,6 +7,8 @@
 #include <linux/blkdev.h>
 #include <linux/scatterlist.h>
 
+#include <trace/events/block.h>
+
 #include "blk.h"
 
 static struct bio *blk_bio_discard_split(struct request_queue *q,
@@ -143,6 +145,7 @@ void blk_queue_split(struct request_queue *q, struct bio **bio,
 		split->bi_rw |= REQ_NOMERGE;
 
 		bio_chain(split, *bio);
+		trace_block_split(q, split, (*bio)->bi_iter.bi_sector);
 		generic_make_request(*bio);
 		*bio = split;
 	}
-- 
1.9.1

Re: [PATCH] block: add call to split trace point

[Jens Axboe]

On 12/03/2015 07:32 AM, Mike Krinkin wrote:
> There is a split tracepoint that is supposed to be called when
> bio is splitted, and it was called in bio_split function until
> commit 4b1faf931650d4a35b2a ("block: Kill bio_pair_split()").
> But now, no one reports splits, so this patch adds call to
> trace_block_split back in blk_queue_split right after split.

Looks good, queued up for 4.5.

-- 
Jens Axboe