[PATCH] block: save page offset gaps in cloned bio

[PATCH] block: save page offset gaps in cloned bio

[Keith Busch]

From: Keith Busch <kbusch@kernel.org>

The cloned bio needs to inherit the accumulated gaps between vectors so
that we can know if this bio can subscribe to the iova coalescing
optimization. The split remainder meanwhile can reset its gaps to 0
since it advanced beyond it and will start accounting from there.

Fixes: 2f6b2565d43c ("block: accumulate memory segment gaps per bio")
Reported-by: Eric Auger <eauger@redhat.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>
---
 block/bio.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/block/bio.c b/block/bio.c
index 898b2f5ef8c81..33aa439c1bae2 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -859,6 +859,7 @@ static int __bio_clone(struct bio *bio, struct bio *bio_src, gfp_t gfp)
 	bio->bi_ioprio = bio_src->bi_ioprio;
 	bio->bi_write_hint = bio_src->bi_write_hint;
 	bio->bi_write_stream = bio_src->bi_write_stream;
+	bio->bi_bvec_gap_bit = bio_src->bi_bvec_gap_bit;
 	bio->bi_iter = bio_src->bi_iter;
 	bio->bi_io_vec = bio_src->bi_io_vec;
 
@@ -1971,6 +1972,7 @@ struct bio *bio_split(struct bio *bio, int sectors,
 		bio_integrity_trim(split);
 
 	bio_advance(bio, split->bi_iter.bi_size);
+	bio->bi_bvec_gap_bit = 0;
 
 	if (bio_flagged(bio, BIO_TRACE_COMPLETION))
 		bio_set_flag(split, BIO_TRACE_COMPLETION);
-- 
2.53.0-Meta

Re: [PATCH] block: save page offset gaps in cloned bio

[Eric Auger]

Hi Keith,

On 8/17/26 6:59 PM, Keith Busch wrote:
> From: Keith Busch <kbusch@kernel.org>
> 
> The cloned bio needs to inherit the accumulated gaps between vectors so
> that we can know if this bio can subscribe to the iova coalescing
> optimization. The split remainder meanwhile can reset its gaps to 0
> since it advanced beyond it and will start accounting from there.
> 
> Fixes: 2f6b2565d43c ("block: accumulate memory segment gaps per bio")
> Reported-by: Eric Auger <eauger@redhat.com>
> Signed-off-by: Keith Busch <kbusch@kernel.org>

Tested-by: Eric Auger <eric.auger@redhat.com>

Many Thanks!

Eric

> ---
>  block/bio.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/block/bio.c b/block/bio.c
> index 898b2f5ef8c81..33aa439c1bae2 100644
> --- a/block/bio.c
> +++ b/block/bio.c
> @@ -859,6 +859,7 @@ static int __bio_clone(struct bio *bio, struct bio *bio_src, gfp_t gfp)
>  	bio->bi_ioprio = bio_src->bi_ioprio;
>  	bio->bi_write_hint = bio_src->bi_write_hint;
>  	bio->bi_write_stream = bio_src->bi_write_stream;
> +	bio->bi_bvec_gap_bit = bio_src->bi_bvec_gap_bit;
>  	bio->bi_iter = bio_src->bi_iter;
>  	bio->bi_io_vec = bio_src->bi_io_vec;
>  
> @@ -1971,6 +1972,7 @@ struct bio *bio_split(struct bio *bio, int sectors,
>  		bio_integrity_trim(split);
>  
>  	bio_advance(bio, split->bi_iter.bi_size);
> +	bio->bi_bvec_gap_bit = 0;
>  
>  	if (bio_flagged(bio, BIO_TRACE_COMPLETION))
>  		bio_set_flag(split, BIO_TRACE_COMPLETION);

Re: [PATCH] block: save page offset gaps in cloned bio

[Christoph Hellwig]

On Mon, Aug 17, 2026 at 09:59:08AM -0700, Keith Busch wrote:
> From: Keith Busch <kbusch@kernel.org>
> 
> The cloned bio needs to inherit the accumulated gaps between vectors so
> that we can know if this bio can subscribe to the iova coalescing
> optimization.

Makes sense.

> The split remainder meanwhile can reset its gaps to 0
> since it advanced beyond it and will start accounting from there.

I don't really understand this part, though.  As in I don't even
understand what you mean here..