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block: add a helper function to merge the segments 

This patch adds a helper function whether a queue can merge
the segments by the DMA MAP layer (e.g. via IOMMU).

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au
Signed-off-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Yoshihiro Shimoda 2019-08-28 21:35:42 +09:00 committed by Christoph Hellwig
parent db91427b65
commit 45147fb522
2 changed files with 25 additions and 0 deletions
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23
block/blk-settings.c
View File

@ -12,6 +12,7 @@
#include <linux/lcm.h>
#include <linux/jiffies.h>
#include <linux/gfp.h>
#include <linux/dma-mapping.h>
#include "blk.h"
#include "blk-wbt.h"
@ -832,6 +833,28 @@ void blk_queue_write_cache(struct request_queue *q, bool wc, bool fua)
}
EXPORT_SYMBOL_GPL(blk_queue_write_cache);
/**
* blk_queue_can_use_dma_map_merging - configure queue for merging segments.
* @q: the request queue for the device
* @dev: the device pointer for dma
*
* Tell the block layer about merging the segments by dma map of @q.
*/
bool blk_queue_can_use_dma_map_merging(struct request_queue *q,
struct device *dev)
{
unsigned long boundary = dma_get_merge_boundary(dev);
if (!boundary)
return false;
/* No need to update max_segment_size. see blk_queue_virt_boundary() */
blk_queue_virt_boundary(q, boundary);
return true;
}
EXPORT_SYMBOL_GPL(blk_queue_can_use_dma_map_merging);
static int __init blk_settings_init(void)
{
blk_max_low_pfn = max_low_pfn - 1;

2
include/linux/blkdev.h
View File

@ -1085,6 +1085,8 @@ extern void blk_queue_dma_alignment(struct request_queue *, int);
extern void blk_queue_update_dma_alignment(struct request_queue *, int);
extern void blk_queue_rq_timeout(struct request_queue *, unsigned int);
extern void blk_queue_write_cache(struct request_queue *q, bool enabled, bool fua);
extern bool blk_queue_can_use_dma_map_merging(struct request_queue *q,
struct device *dev);
/*
* Number of physical segments as sent to the device.