libata: eliminate the home grown dma padding in favour of
that provided by the block layer
ATA requires that all DMA transfers begin and end on word boundaries.
Because of this, a large amount of machinery grew up in ide to adjust
scatterlists on this basis. However, as of 2.5, the block layer has a
dma_alignment variable which ensures both the beginning and length of a
DMA transfer are aligned on the dma_alignment boundary. Although the
block layer does adjust the beginning of the transfer to ensure this
happens, it doesn't actually adjust the length, it merely makes sure
that space is allocated for transfers beyond the declared length. The
upshot of this is that scatterlists may be padded to any size between
the actual length and the length adjusted to the dma_alignment safely
knowing that memory is allocated in this region.
Right at the moment, SCSI takes the default dma_aligment which is on a
512 byte boundary. Note that this aligment only applies to transfers
coming in from user space. However, since all kernel allocations are
automatically aligned on a minimum of 32 byte boundaries, it is safe to
adjust them in this manner as well.
tj: * Adjusting sg after padding is done in block layer. Make libata
set queue alignment correctly for ATAPI devices and drop broken
sg mangling from ata_sg_setup().
* Use request->raw_data_len for ATAPI transfer chunk size.
* Killed qc->raw_nbytes.
* Separated out killing qc->n_iter.
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/include/linux/libata.h b/include/linux/libata.h
index bc5a8d0..2e098f9 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -278,7 +278,6 @@
/* size of buffer to pad xfers ending on unaligned boundaries */
ATA_DMA_PAD_SZ = 4,
- ATA_DMA_PAD_BUF_SZ = ATA_DMA_PAD_SZ * ATA_MAX_QUEUE,
/* ering size */
ATA_ERING_SIZE = 32,
@@ -457,24 +456,18 @@
unsigned long flags; /* ATA_QCFLAG_xxx */
unsigned int tag;
unsigned int n_elem;
- unsigned int mapped_n_elem;
int dma_dir;
- unsigned int pad_len;
unsigned int sect_size;
unsigned int nbytes;
- unsigned int raw_nbytes;
unsigned int curbytes;
struct scatterlist *cursg;
unsigned int cursg_ofs;
- struct scatterlist *last_sg;
- struct scatterlist saved_last_sg;
struct scatterlist sgent;
- struct scatterlist extra_sg[2];
struct scatterlist *sg;
@@ -619,9 +612,6 @@
struct ata_prd *prd; /* our SG list */
dma_addr_t prd_dma; /* and its DMA mapping */
- void *pad; /* array of DMA pad buffers */
- dma_addr_t pad_dma;
-
struct ata_ioports ioaddr; /* ATA cmd/ctl/dma register blocks */
u8 ctl; /* cache of ATA control register */
@@ -1363,12 +1353,9 @@
qc->flags = 0;
qc->cursg = NULL;
qc->cursg_ofs = 0;
- qc->nbytes = qc->raw_nbytes = qc->curbytes = 0;
+ qc->nbytes = qc->curbytes = 0;
qc->n_elem = 0;
- qc->mapped_n_elem = 0;
qc->err_mask = 0;
- qc->pad_len = 0;
- qc->last_sg = NULL;
qc->sect_size = ATA_SECT_SIZE;
ata_tf_init(qc->dev, &qc->tf);
@@ -1423,19 +1410,6 @@
return mask;
}
-static inline int ata_pad_alloc(struct ata_port *ap, struct device *dev)
-{
- ap->pad_dma = 0;
- ap->pad = dmam_alloc_coherent(dev, ATA_DMA_PAD_BUF_SZ,
- &ap->pad_dma, GFP_KERNEL);
- return (ap->pad == NULL) ? -ENOMEM : 0;
-}
-
-static inline void ata_pad_free(struct ata_port *ap, struct device *dev)
-{
- dmam_free_coherent(dev, ATA_DMA_PAD_BUF_SZ, ap->pad, ap->pad_dma);
-}
-
static inline struct ata_port *ata_shost_to_port(struct Scsi_Host *host)
{
return *(struct ata_port **)&host->hostdata[0];