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block: accumulate memory segment gaps per bio

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The blk-mq dma iterator has an optimization for requests that align to
the device's iommu merge boundary. This boundary may be larger than the
device's virtual boundary, but the code had been depending on that queue
limit to know ahead of time if the request is guaranteed to align to
that optimization.

Rather than rely on that queue limit, which many devices may not report,
save the lowest set bit of any boundary gap between each segment in the
bio while checking the segments. The request stores the value for
merging and quickly checking per io if the request can use iova
optimizations.

Signed-off-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Keith Busch
2025-10-14 08:04:55 -07:00
committed by Jens Axboe
parent 0739c2c6a0
commit 2f6b2565d4
8 changed files with 77 additions and 5 deletions
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3
block/blk-mq-dma.c
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@@ -79,8 +79,7 @@ static bool blk_map_iter_next(struct request *req, struct blk_map_iter *iter,
static inline bool blk_can_dma_map_iova(struct request *req,
struct device *dma_dev)
{
return !((queue_virt_boundary(req->q) + 1) &
dma_get_merge_boundary(dma_dev));
return !(req_phys_gap_mask(req) & dma_get_merge_boundary(dma_dev));
}
static bool blk_dma_map_bus(struct blk_dma_iter *iter, struct phys_vec *vec)