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Commit e3790c7d authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe
Browse files

block: separate out padding from alignment 



Block layer alignment was used for two different purposes - memory
alignment and padding.  This causes problems in lower layers because
drivers which only require memory alignment ends up with adjusted
rq->data_len.  Separate out padding such that padding occurs iff
driver explicitly requests it.

Tomo: restorethe code to update bio in blk_rq_map_user
      introduced by the commit 40b01b9b
      according to padding alignment.

Signed-off-by: default avatarTejun Heo <htejun@gmail.com>
Signed-off-by: default avatarFUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent 7a85f889

block/blk-map.c

+13 −7
Original line number Diff line number Diff line
@@ -43,6 +43,7 @@ static int __blk_rq_map_user(struct request_queue *q, struct request *rq, 
			     void __user *ubuf, unsigned int len)

{

	unsigned long uaddr;

	unsigned int alignment;

	struct bio *bio, *orig_bio;

	int reading, ret;
@@ -53,8 +54,8 @@ static int __blk_rq_map_user(struct request_queue *q, struct request *rq, 
	 * direct dma. else, set up kernel bounce buffers

	 */

	uaddr = (unsigned long) ubuf;

	if (!(uaddr & queue_dma_alignment(q)) &&

	    !(len & queue_dma_alignment(q)))

	alignment = queue_dma_alignment(q) | q->dma_pad_mask;

	if (!(uaddr & alignment) && !(len & alignment))

		bio = bio_map_user(q, NULL, uaddr, len, reading);

	else

		bio = bio_copy_user(q, uaddr, len, reading);
@@ -141,15 +142,20 @@ int blk_rq_map_user(struct request_queue *q, struct request *rq, 


	/*

	 * __blk_rq_map_user() copies the buffers if starting address

	 * or length isn't aligned.  As the copied buffer is always

	 * page aligned, we know that there's enough room for padding.

	 * Extend the last bio and update rq->data_len accordingly.

	 * or length isn't aligned to dma_pad_mask.  As the copied

	 * buffer is always page aligned, we know that there's enough

	 * room for padding.  Extend the last bio and update

	 * rq->data_len accordingly.

	 *

	 * On unmap, bio_uncopy_user() will use unmodified

	 * bio_map_data pointed to by bio->bi_private.

	 */

	if (len & queue_dma_alignment(q)) {

		unsigned int pad_len = (queue_dma_alignment(q) & ~len) + 1;

	if (len & q->dma_pad_mask) {

		unsigned int pad_len = (q->dma_pad_mask & ~len) + 1;

		struct bio *bio = rq->biotail;



		bio->bi_io_vec[bio->bi_vcnt - 1].bv_len += pad_len;

		bio->bi_size += pad_len;



		rq->extra_len += pad_len;

	}

block/blk-settings.c

+17 −0
Original line number Diff line number Diff line
@@ -292,6 +292,23 @@ void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b) 
}

EXPORT_SYMBOL(blk_queue_stack_limits);



/**

 * blk_queue_dma_pad - set pad mask

 * @q:     the request queue for the device

 * @mask:  pad mask

 *

 * Set pad mask.  Direct IO requests are padded to the mask specified.

 *

 * 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().

 **/

void blk_queue_dma_pad(struct request_queue *q, unsigned int mask)

{

	q->dma_pad_mask = mask;

}

EXPORT_SYMBOL(blk_queue_dma_pad);



/**

 * blk_queue_dma_drain - Set up a drain buffer for excess dma.

 * @q:  the request queue for the device

drivers/ata/libata-scsi.c

+2 −1
Original line number Diff line number Diff line
@@ -862,9 +862,10 @@ static int ata_scsi_dev_config(struct scsi_device *sdev, 
		struct request_queue *q = sdev->request_queue;

		void *buf;



		/* set the min alignment */

		/* 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);



		/* configure draining */

		buf = kmalloc(ATAPI_MAX_DRAIN, q->bounce_gfp | GFP_KERNEL);

include/linux/blkdev.h

+2 −0
Original line number Diff line number Diff line
@@ -362,6 +362,7 @@ struct request_queue 
	unsigned long		seg_boundary_mask;

	void			*dma_drain_buffer;

	unsigned int		dma_drain_size;

	unsigned int		dma_pad_mask;

	unsigned int		dma_alignment;



	struct blk_queue_tag	*queue_tags;
@@ -701,6 +702,7 @@ 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 void blk_queue_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);