Re: [PATCH 5/5] virtio-blk: Consider virtio_max_dma_size() for maximum segment size
From: Joerg Roedel <joro@8bytes.org>
Date: 2019-01-24 09:51:55
Also in:
linux-iommu, lkml
Subsystem:
block layer, the rest · Maintainers:
Jens Axboe, Linus Torvalds
On Thu, Jan 24, 2019 at 09:42:21AM +0100, Christoph Hellwig wrote:
Yes. But more importantly it would fix the limit for all other block drivers that set large segment sizes when running over swiotlb.
True, so it would be something like the diff below? I havn't worked on the block layer, so I don't know if that needs additional checks for ->dev or anything.
diff --git a/block/blk-settings.c b/block/blk-settings.c
index 3e7038e475ee..9a927280c904 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c@@ -1,6 +1,7 @@ /* * Functions related to setting various queue properties from drivers */ +#include <linux/dma-mapping.h> #include <linux/kernel.h> #include <linux/module.h> #include <linux/init.h>
@@ -303,13 +304,17 @@ EXPORT_SYMBOL_GPL(blk_queue_max_discard_segments); **/ void blk_queue_max_segment_size(struct request_queue *q, unsigned int max_size) { + unsigned int dma_max_size; + if (max_size < PAGE_SIZE) { max_size = PAGE_SIZE; printk(KERN_INFO "%s: set to minimum %d\n", __func__, max_size); } - q->limits.max_segment_size = max_size; + dma_max_size = dma_max_mapping_size(q->backing_dev_info->dev); + + q->limits.max_segment_size = min(max_size, dma_max_size); } EXPORT_SYMBOL(blk_queue_max_segment_size);