Misc ATAPI commands may try to transfer more bytes than requested.
For PIO which is performed by libata HSM, this is worked around by
draining extra bytes from __atapi_pio_bytes().
This patch implements drain buffer to perform draining for DMA and
PIO-over-DMA cases. One page is allocated w/ GFP_DMA32 during libata
core layer initialization. On host registration, this drain page is
DMA mapped and ATAPI_MAX_DRAIN_PAGES sg entries are reserved.
ata_sg_setup_extra() uses these extra sg entries to map the drain page
ATAPI_MAX_DRAIN_PAGES times, extending sg list by ATAPI_MAX_DRAIN
bytes. This allows both DMA and PIO-over-DMA misc ATAPI commands to
overflow by ATAPI_MAX_DRAIN bytes just like PIO commands.
Signed-off-by: Tejun Heo <htejun@xxxxxxxxx>
---
drivers/ata/libata-core.c | 116 ++++++++++++++++++++++++++++++++++++++++-----
drivers/ata/libata-scsi.c | 14 ++++--
include/linux/libata.h | 4 +-
3 files changed, 116 insertions(+), 18 deletions(-)
diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 9bc89a6..1a81e22 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -4759,6 +4759,60 @@ void ata_sg_init(struct ata_queued_cmd *qc, struct scatterlist *sg,
qc->cursg = qc->sg;
}
+/**
+ * ata_sg_setup_extra - Setup extra sg entries
+ * @qc: Command to setup extra sg entries for
+ * @n_elem_extra: Out parameter for the number of extra sg entries
+ * @nbytes_extra: Out parameter for the number of extra bytes
+ *
+ * Extra sg entries are used to deal with ATAPI peculiarities.
+ * First, the content to be transferred can be of any size but
+ * transfer length should be aligned to 4 bytes, so if data size
+ * isn't aligned, it needs to be padded.
+ *
+ * Second, for commands whose repsonse can be variable, due to
+ * userland bugs (more likely) and hardware bugs, devices can try
+ * to transfer more bytes than requested. This can be worked
+ * around by appending drain buffers at the end.
+ *
+ * This function sets up both padding and draining sg entries.
+ * For this purpose, each qc has 2 + ATAPI_MAX_DRAIN_PAGES extra
+ * sg entries. Each extra sg has assigned function.
+ *
+ * e[0] | e[1] | e[2] | ... | e[2 + ATAPI_MAX_DRAIN_PAGES - 1]
+ * ----------------------------------------------------------------------
+ * link | padding | draining ...
+ * or link
+ *
+ * After sg setup is complete, sg list looks like the following.
+ *
+ * 1. Padding necessary, padding doesn't replace the last sg
+ *
+ * o[0][1][2]...[last] e[0][1]([2]... if draining is necessary)
+ * | ^
+ * \------/
+ * e[0] carries the original content of o[last].
+ *
+ * 2. Padding necessary, padding replaces the last sg
+ *
+ * o[0][1][2]...[last] e[0][1]([2]... if draining is necessary)
+ * | ^
+ * \---------/
+ * e[1] completely includes what o[last] used to point to.
+ *
+ * 3. Only draining is necessary.
+ *
+ * [0][1][2]...[last] e[0][1][2]...
+ * | ^
+ * \---------/
+ * e[1] carries the original conetent of o[last].
+ *
+ * LOCKING:
+ * spin_lock_irqsave(host lock)
+ *
+ * RETURNS:
+ * Adjusted n_elem which should be mapped.
+ */
static unsigned int ata_sg_setup_extra(struct ata_queued_cmd *qc,
unsigned int *n_elem_extra,
unsigned int *nbytes_extra)
@@ -4766,6 +4820,7 @@ static unsigned int ata_sg_setup_extra(struct ata_queued_cmd *qc,
struct ata_port *ap = qc->ap;
unsigned int n_elem = qc->n_elem;
struct scatterlist *lsg, *copy_lsg = NULL, *tsg = NULL, *esg = NULL;
+ int drain;
*n_elem_extra = 0;
*nbytes_extra = 0;
@@ -4773,7 +4828,10 @@ static unsigned int ata_sg_setup_extra(struct ata_queued_cmd *qc,
/* needs padding? */
qc->pad_len = qc->nbytes & 3;
- if (likely(!qc->pad_len))
+ /* needs drain? */
+ drain = atapi_qc_may_overflow(qc);
+
+ if (likely(!qc->pad_len && !drain))
return n_elem;
/* locate last sg and save it */
@@ -4835,6 +4893,29 @@ static unsigned int ata_sg_setup_extra(struct ata_queued_cmd *qc,
(*nbytes_extra) += 4 - qc->pad_len;
}
+ if (drain) {
+ struct scatterlist *dsg = qc->extra_sg + 2;
+ int i;
+
+ for (i = 0; i < ATAPI_MAX_DRAIN_PAGES; i++) {
+ sg_set_page(dsg, virt_to_page(ata_drain_page),
+ PAGE_SIZE, 0);
+ sg_dma_address(dsg) = ap->host->drain_page_dma;
+ sg_dma_len(dsg) = PAGE_SIZE;
+ dsg++;
+ }
+
+ if (!tsg) {
+ copy_lsg = &qc->extra_sg[1];
+ tsg = &qc->extra_sg[1];
+ }
+
+ esg = dsg - 1;
+
+ (*n_elem_extra) += ATAPI_MAX_DRAIN_PAGES;
+ (*nbytes_extra) += ATAPI_MAX_DRAIN_PAGES * PAGE_SIZE;
+ }
+
if (copy_lsg)
sg_set_page(copy_lsg, sg_page(lsg), lsg->length, lsg->offset);
@@ -6892,6 +6973,9 @@ static void ata_host_stop(struct device *gendev, void *res)
ap->ops->port_stop(ap);
}
+ dma_unmap_single(host->dev, host->drain_page_dma, PAGE_SIZE,
+ DMA_FROM_DEVICE);
+
if (host->ops->host_stop)
host->ops->host_stop(host);
}
@@ -6914,8 +6998,8 @@ static void ata_host_stop(struct device *gendev, void *res)
*/
int ata_host_start(struct ata_host *host)
{
- int have_stop = 0;
void *start_dr = NULL;
+ dma_addr_t dma;
int i, rc;
if (host->flags & ATA_HOST_STARTED)
@@ -6926,20 +7010,23 @@ int ata_host_start(struct ata_host *host)
if (!host->ops && !ata_port_is_dummy(ap))
host->ops = ap->ops;
-
- if (ap->ops->port_stop)
- have_stop = 1;
}
- if (host->ops->host_stop)
- have_stop = 1;
+ start_dr = devres_alloc(ata_host_stop, 0, GFP_KERNEL);
+ if (!start_dr)
+ return -ENOMEM;
- if (have_stop) {
- start_dr = devres_alloc(ata_host_stop, 0, GFP_KERNEL);
- if (!start_dr)
- return -ENOMEM;
+ /* map drain page */
+ dma = dma_map_single(host->dev, ata_drain_page, PAGE_SIZE,
+ DMA_FROM_DEVICE);
+ if (dma_mapping_error(dma)) {
+ dev_printk(KERN_ERR, host->dev, "failed to map drain page\n");
+ rc = -ENOMEM;
+ goto err_map;
}
+ host->drain_page_dma = dma;
+ /* start ports */
for (i = 0; i < host->n_ports; i++) {
struct ata_port *ap = host->ports[i];
@@ -6948,7 +7035,7 @@ int ata_host_start(struct ata_host *host)
if (rc) {
if (rc != -ENODEV)
dev_printk(KERN_ERR, host->dev, "failed to start port %d (errno=%d)\n", i, rc);
- goto err_out;
+ goto err_start;
}
}
ata_eh_freeze_port(ap);
@@ -6959,13 +7046,16 @@ int ata_host_start(struct ata_host *host)
host->flags |= ATA_HOST_STARTED;
return 0;
- err_out:
+ err_start:
while (--i >= 0) {
struct ata_port *ap = host->ports[i];
if (ap->ops->port_stop)
ap->ops->port_stop(ap);
}
+ err_map:
+ dma_unmap_single(host->dev, host->drain_page_dma, PAGE_SIZE,
+ DMA_FROM_DEVICE);
devres_free(start_dr);
return rc;
}
diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index f523e66..f07704c 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -832,13 +832,19 @@ static void ata_scsi_dev_config(struct scsi_device *sdev,
/* configure max sectors */
blk_queue_max_sectors(sdev->request_queue, dev->max_sectors);
- /* SATA DMA transfers must be multiples of 4 byte, so
- * we need to pad ATAPI transfers using an extra sg.
- * Decrement max hw segments accordingly.
+ /* SATA DMA transfers must be multiples of 4 byte, so we need
+ * to pad ATAPI transfers using an extra sg. Also, ATAPI
+ * commands with variable length reponse needs draining of
+ * extra data. Decrement max hw segments accordingly.
*/
if (dev->class == ATA_DEV_ATAPI) {
struct request_queue *q = sdev->request_queue;
- blk_queue_max_hw_segments(q, q->max_hw_segments - 1);
+ unsigned short hw_segments = q->max_hw_segments;
+
+ BUG_ON(hw_segments <= 1 + ATAPI_MAX_DRAIN_PAGES);
+ hw_segments -= 1 + ATAPI_MAX_DRAIN_PAGES;
+
+ blk_queue_max_hw_segments(q, hw_segments);
}
if (dev->flags & ATA_DFLAG_AN)
diff --git a/include/linux/libata.h b/include/linux/libata.h
index f0017fc..73080d9 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -121,6 +121,7 @@ enum {
ATA_SHORT_PAUSE = (HZ >> 6) + 1,
ATAPI_MAX_DRAIN = 16 << 10,
+ ATAPI_MAX_DRAIN_PAGES = ATAPI_MAX_DRAIN >> PAGE_SHIFT,
ATA_SHT_EMULATED = 1,
ATA_SHT_CMD_PER_LUN = 1,
@@ -438,6 +439,7 @@ struct ata_host {
void *private_data;
const struct ata_port_operations *ops;
unsigned long flags;
+ dma_addr_t drain_page_dma;
#ifdef CONFIG_ATA_ACPI
acpi_handle acpi_handle;
#endif
@@ -476,7 +478,7 @@ struct ata_queued_cmd {
struct scatterlist *last_sg;
struct scatterlist saved_last_sg;
struct scatterlist sgent;
- struct scatterlist extra_sg[2];
+ struct scatterlist extra_sg[2 + ATAPI_MAX_DRAIN_PAGES];
struct scatterlist *sg;
--
1.5.2.4
-
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