[PATCH 2/4] block: add blk_queue_update_dma_pad

FUJITA Tomonori
2008-05-20T05:04:11Z

This adds blk_queue_update_dma_pad to prevent LLDs from overwriting
the dma pad mask wrongly (we added blk_queue_update_dma_alignment due
to the same reason).

This also converts libata to use blk_queue_update_dma_pad instead of
blk_queue_dma_pad.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Tejun Heo <htejun@gmail.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
---
block/blk-settings.c | 24 ++++++++++++++++++++----
drivers/ata/libata-scsi.c | 3 ++-
include/linux/blkdev.h | 1 +
3 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/block/blk-settings.c b/block/blk-settings.c
index 781d1bf..941777c 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -308,11 +308,10 @@ EXPORT_SYMBOL(blk_queue_stack_limits);
* @q: the request queue for the device
* @mask: pad mask
*
- * Set pad mask. Direct IO requests are padded to the mask specified.
+ * Set dma pad mask.
*
- * Appending pad buffer to a request modifies ->data_len such that it
- * includes the pad buffer. The original requested data length can be
- * obtained using blk_rq_raw_data_len().
+ * Appending pad buffer to a request modifies the last entry of a
+ * scatter list such that it includes the pad buffer.
**/
void blk_queue_dma_pad(struct request_queue *q, unsigned int mask)
{
@@ -321,6 +320,23 @@ void blk_queue_dma_pad(struct request_queue *q, unsigned int mask)
EXPORT_SYMBOL(blk_queue_dma_pad);

/**
+ * blk_queue_update_dma_pad - update pad mask
+ * @q: the request queue for the device
+ * @mask: pad mask
+ *
+ * Update dma pad mask.
+ *
+ * Appending pad buffer to a request modifies the last entry of a
+ * scatter list such that it includes the pad buffer.
+ **/
+void blk_queue_update_dma_pad(struct request_queue *q, unsigned int mask)
+{
+ if (mask > q->dma_pad_mask)
+ q->dma_pad_mask = mask;
+}
+EXPORT_SYMBOL(blk_queue_update_dma_pad);
+
+/**
* 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
diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index aeb6e01..60c0e28 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -885,7 +885,8 @@ static int ata_scsi_dev_config(struct scsi_device *sdev,
/* set the min alignment and padding */
blk_queue_update_dma_alignment(sdev->request_queue,
ATA_DMA_PAD_SZ - 1);
- blk_queue_dma_pad(sdev->request_queue, ATA_DMA_PAD_SZ - 1);
+ blk_queue_update_dma_pad(sdev->request_queue,
+ ATA_DMA_PAD_SZ - 1);

/* configure draining */
buf = kmalloc(ATAPI_MAX_DRAIN, q->bounce_gfp | GFP_KERNEL);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index d2a1b71..740d68f 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -749,6 +749,7 @@ 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 void blk_queue_dma_pad(struct request_queue *, unsigned int);
+extern void blk_queue_update_dma_pad(struct request_queue *, unsigned int);
extern int blk_queue_dma_drain(struct request_queue *q,
dma_drain_needed_fn *dma_drain_needed,
void *buf, unsigned int size);
--
1.5.4.2