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[PATCH] libata: make ata_sg_setup_one() trim zero length sg

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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: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>
This commit is contained in:
Tejun Heo 2006-02-20 23:48:38 +09:00 committed by Jeff Garzik
parent cc1887f3d8
commit 2e242fa994
1 changed files with 8 additions and 5 deletions
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13
drivers/scsi/libata-core.c
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@ -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");