Re: [PATCHv5 1/2] block: accumulate memory segment gaps per bio

Keith Busch
2025-11-11T13:54:56Z

On Tue, Nov 11, 2025 at 02:40:01PM +0100, Christoph Hellwig wrote:
> On Tue, Nov 11, 2025 at 08:25:38AM -0500, Keith Busch wrote:
> > Ah, so we're merging a discard for a device that doesn't support
> > vectored discard. I think we still want to be able to front/back merge
> > such requests, though.
>
> Yes, but purely based on bi_sector/bi_size, not based on the payload.

This should do it:

---
diff --git a/block/blk-merge.c b/block/blk-merge.c
index 3ca6fbf8b7870..d3115d7469df0 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -737,6 +737,9 @@ u8 bio_seg_gap(struct request_queue *q, struct bio *prev, struct bio *next,
{
struct bio_vec pb, nb;

+ if (!bio_has_data(prev))
+ return 0;
+
gaps_bit = min_not_zero(gaps_bit, prev->bi_bvec_gap_bit);
gaps_bit = min_not_zero(gaps_bit, next->bi_bvec_gap_bit);

--