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Commit 2e242fa9 authored by Tejun Heo's avatar Tejun Heo Committed by Jeff Garzik
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[PATCH] libata: make ata_sg_setup_one() trim zero length sg 



This patch makes ata_sg_setup_one() trim sg entry (thus making
qc->n_elem zero) if padding results in zero length sg entry.

Signed-off-by: default avatarTejun Heo <htejun@gmail.com>
Signed-off-by: default avatarJeff Garzik <jgarzik@pobox.com>
parent cc1887f3

drivers/scsi/libata-core.c

+8 −5
Original line number Diff line number Diff line
@@ -2514,7 +2514,7 @@ static void ata_sg_clean(struct ata_queued_cmd *qc) 
	assert(sg != NULL);



	if (qc->flags & ATA_QCFLAG_SINGLE)

		assert(qc->n_elem == 1);

		assert(qc->n_elem <= 1);



	VPRINTK("unmapping %u sg elements\n", qc->n_elem);
@@ -2537,7 +2537,7 @@ static void ata_sg_clean(struct ata_queued_cmd *qc) 
			kunmap_atomic(addr, KM_IRQ0);

		}

	} else {

		if (sg_dma_len(&sg[0]) > 0)

		if (qc->n_elem)

			dma_unmap_single(ap->host_set->dev,

				sg_dma_address(&sg[0]), sg_dma_len(&sg[0]),

				dir);
@@ -2715,6 +2715,7 @@ static int ata_sg_setup_one(struct ata_queued_cmd *qc) 
	int dir = qc->dma_dir;

	struct scatterlist *sg = qc->__sg;

	dma_addr_t dma_address;

	int trim_sg = 0;



	/* we must lengthen transfers to end on a 32-bit boundary */

	qc->pad_len = sg->length & 3;
@@ -2734,13 +2735,15 @@ static int ata_sg_setup_one(struct ata_queued_cmd *qc) 
		sg_dma_len(psg) = ATA_DMA_PAD_SZ;

		/* trim sg */

		sg->length -= qc->pad_len;

		if (sg->length == 0)

			trim_sg = 1;



		DPRINTK("padding done, sg->length=%u pad_len=%u\n",

			sg->length, qc->pad_len);

	}



	if (!sg->length) {

		sg_dma_address(sg) = 0;

	if (trim_sg) {

		qc->n_elem--;

		goto skip_map;

	}
@@ -2753,9 +2756,9 @@ static int ata_sg_setup_one(struct ata_queued_cmd *qc) 
	}



	sg_dma_address(sg) = dma_address;

skip_map:

	sg_dma_len(sg) = sg->length;



skip_map:

	DPRINTK("mapped buffer of %d bytes for %s\n", sg_dma_len(sg),

		qc->tf.flags & ATA_TFLAG_WRITE ? "write" : "read");