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authorLinus Torvalds <torvalds@linux-foundation.org>2008-01-29 08:51:56 +1100
committerLinus Torvalds <torvalds@linux-foundation.org>2008-01-29 08:51:56 +1100
commit8d01eddf292dcd78b640418c80fb300532799cd4 (patch)
treedd7f816423463e5ad10f15af22fdbd5b75cc6184 /block/ll_rw_blk.c
parentf0f0052069989b80d2a3e50c9cd2f2a650bc1aea (diff)
parentfa0ccd837e3dddb44c7db2f128a8bb7e4eabc21a (diff)
downloadop-kernel-dev-8d01eddf292dcd78b640418c80fb300532799cd4.zip
op-kernel-dev-8d01eddf292dcd78b640418c80fb300532799cd4.tar.gz
Merge branch 'for-2.6.25' of git://git.kernel.dk/linux-2.6-block
* 'for-2.6.25' of git://git.kernel.dk/linux-2.6-block: block: implement drain buffers __bio_clone: don't calculate hw/phys segment counts block: allow queue dma_alignment of zero blktrace: Add blktrace ioctls to SCSI generic devices
Diffstat (limited to 'block/ll_rw_blk.c')
-rw-r--r--block/ll_rw_blk.c49
1 files changed, 49 insertions, 0 deletions
diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
index c16fdfe..1932a56 100644
--- a/block/ll_rw_blk.c
+++ b/block/ll_rw_blk.c
@@ -721,6 +721,45 @@ void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b)
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
+ * @buf: physically contiguous buffer
+ * @size: size of the buffer in bytes
+ *
+ * Some devices have excess DMA problems and can't simply discard (or
+ * zero fill) the unwanted piece of the transfer. They have to have a
+ * real area of memory to transfer it into. The use case for this is
+ * ATAPI devices in DMA mode. If the packet command causes a transfer
+ * bigger than the transfer size some HBAs will lock up if there
+ * aren't DMA elements to contain the excess transfer. What this API
+ * does is adjust the queue so that the buf is always appended
+ * silently to the scatterlist.
+ *
+ * Note: This routine adjusts max_hw_segments to make room for
+ * appending the drain buffer. If you call
+ * blk_queue_max_hw_segments() or blk_queue_max_phys_segments() after
+ * calling this routine, you must set the limit to one fewer than your
+ * 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)
+{
+ 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_buffer = buf;
+ q->dma_drain_size = size;
+
+ return 0;
+}
+
+EXPORT_SYMBOL_GPL(blk_queue_dma_drain);
+
+/**
* blk_queue_segment_boundary - set boundary rules for segment merging
* @q: the request queue for the device
* @mask: the memory boundary mask
@@ -1374,6 +1413,16 @@ new_segment:
bvprv = bvec;
} /* segments in rq */
+ if (q->dma_drain_size) {
+ sg->page_link &= ~0x02;
+ sg = sg_next(sg);
+ sg_set_page(sg, virt_to_page(q->dma_drain_buffer),
+ q->dma_drain_size,
+ ((unsigned long)q->dma_drain_buffer) &
+ (PAGE_SIZE - 1));
+ nsegs++;
+ }
+
if (sg)
sg_mark_end(sg);
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