Draining shouldn't be done for commands where overflow may indicate
data integrity issues. Add dma_drain_needed callback to
request_queue. Drain buffer is appened iff this function returns
non-zero.
Signed-off-by: Tejun Heo <htejun@xxxxxxxxx>
Cc: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
---
block/blk-merge.c | 2 +-
block/blk-settings.c | 7 +++++--
include/linux/blkdev.h | 7 +++++--
3 files changed, 11 insertions(+), 5 deletions(-)
diff --git a/block/blk-merge.c b/block/blk-merge.c
index 480d2bc..d50cfc8 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -220,7 +220,7 @@ new_segment:
bvprv = bvec;
} /* segments in rq */
- if (q->dma_drain_size) {
+ if (q->dma_drain_size && q->dma_drain_needed(rq)) {
sg->page_link &= ~0x02;
sg = sg_next(sg);
sg_set_page(sg, virt_to_page(q->dma_drain_buffer),
diff --git a/block/blk-settings.c b/block/blk-settings.c
index c8d0c57..0a0b3a4 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -296,6 +296,7 @@ EXPORT_SYMBOL(blk_queue_stack_limits);
* blk_queue_dma_drain - Set up a drain buffer for excess dma.
*
* @q: the request queue for the device
+ * @dma_drain_needed: fn which returns non-zero if drain is necessary
* @buf: physically contiguous buffer
* @size: size of the buffer in bytes
*
@@ -315,14 +316,16 @@ EXPORT_SYMBOL(blk_queue_stack_limits);
* device can support otherwise there won't be room for the drain
* buffer.
*/
-int blk_queue_dma_drain(struct request_queue *q, void *buf,
- unsigned int size)
+extern int blk_queue_dma_drain(struct request_queue *q,
+ dma_drain_needed_fn *dma_drain_needed,
+ void *buf, unsigned int size)
{
if (q->max_hw_segments < 2 || q->max_phys_segments < 2)
return -EINVAL;
/* make room for appending the drain */
--q->max_hw_segments;
--q->max_phys_segments;
+ q->dma_drain_needed = dma_drain_needed;
q->dma_drain_buffer = buf;
q->dma_drain_size = size;
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index ee0b021..3912c5d 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -257,6 +257,7 @@ struct bio_vec;
typedef int (merge_bvec_fn) (struct request_queue *, struct bio *, struct bio_vec *);
typedef void (prepare_flush_fn) (struct request_queue *, struct request *);
typedef void (softirq_done_fn)(struct request *);
+typedef int (dma_drain_needed_fn)(struct request *);
enum blk_queue_state {
Queue_down,
@@ -293,6 +294,7 @@ struct request_queue
merge_bvec_fn *merge_bvec_fn;
prepare_flush_fn *prepare_flush_fn;
softirq_done_fn *softirq_done_fn;
+ dma_drain_needed_fn *dma_drain_needed;
/*
* Dispatch queue sorting
@@ -697,8 +699,9 @@ extern void blk_queue_max_hw_segments(struct request_queue *, unsigned short);
extern void blk_queue_max_segment_size(struct request_queue *, unsigned int);
extern void blk_queue_hardsect_size(struct request_queue *, unsigned short);
extern void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b);
-extern int blk_queue_dma_drain(struct request_queue *q, void *buf,
- unsigned int size);
+extern int blk_queue_dma_drain(struct request_queue *q,
+ dma_drain_needed_fn *dma_drain_needed,
+ void *buf, unsigned int size);
extern void blk_queue_segment_boundary(struct request_queue *, unsigned long);
extern void blk_queue_prep_rq(struct request_queue *, prep_rq_fn *pfn);
extern void blk_queue_merge_bvec(struct request_queue *, merge_bvec_fn *);
--
1.5.2.4
-
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