This patch fixes an issue that the following error happens on
swiotlb environment:
xhci-hcd ee000000.usb: swiotlb buffer is full (sz: 524288 bytes), total 32768 (slots), used 1338 (slots)
On the kernel v5.1, block settings of a usb-storage with SuperSpeed
were the following so that the block layer will allocate buffers
up to 64 KiB, and then the issue didn't happen.
max_segment_size = 65536
max_hw_sectors_kb = 1024
After the commit 09324d32d2a0 ("block: force an unlimited segment
size on queues with a virt boundary") is applied, the block settings
are the following. So, the block layer will allocate buffers up to
1024 KiB, and then the issue happens:
max_segment_size = 4294967295
max_hw_sectors_kb = 1024
To fix the issue, the usb-storage driver checks the maximum size of
a mapping for the device and then adjusts the max_hw_sectors_kb
if required. After this patch is applied, the block settings will
be the following, and then the issue doesn't happen.
max_segment_size = 4294967295
max_hw_sectors_kb = 256
Fixes: 09324d32d2a0 ("block: force an unlimited segment size on queues with a virt boundary")
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx>
---
Changes from v1:
- Call blk_queue_max_hw_sectors() for the maximum size of mapping
unconditionally to simplify the code by using read the value back
from the queue in the end.
- Add a comment on the code.
- On v1, I got Reviewed-by from Christoph. But, I changed the code a little,
I removed the Reviewed-by.
drivers/usb/storage/scsiglue.c | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/drivers/usb/storage/scsiglue.c b/drivers/usb/storage/scsiglue.c
index 59190d8..556bb4f 100644
--- a/drivers/usb/storage/scsiglue.c
+++ b/drivers/usb/storage/scsiglue.c
@@ -28,6 +28,8 @@
* status of a command.
*/
+#include <linux/blkdev.h>
+#include <linux/dma-mapping.h>
#include <linux/module.h>
#include <linux/mutex.h>
@@ -99,6 +101,7 @@ static int slave_alloc (struct scsi_device *sdev)
static int slave_configure(struct scsi_device *sdev)
{
struct us_data *us = host_to_us(sdev->host);
+ struct device *dev = us->pusb_dev->bus->sysdev;
/*
* Many devices have trouble transferring more than 32KB at a time,
@@ -129,6 +132,14 @@ static int slave_configure(struct scsi_device *sdev)
}
/*
+ * The max_hw_sectors should be up to maximum size of a mapping for
+ * the device. Otherwise, a DMA API might fail on swiotlb environment.
+ */
+ blk_queue_max_hw_sectors(sdev->request_queue,
+ min_t(size_t, queue_max_hw_sectors(sdev->request_queue),
+ dma_max_mapping_size(dev) >> SECTOR_SHIFT));
+
+ /*
* Some USB host controllers can't do DMA; they have to use PIO.
* They indicate this by setting their dma_mask to NULL. For
* such controllers we need to make sure the block layer sets
--
2.7.4
