This is a note to let you know that I've just added the patch titled

usb-storage: Add a limitation for blk_queue_max_hw_sectors()

to my usb git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git in the usb-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

From d74ffae8b8dd17eaa8b82fc163e6aa2076dc8fb1 Mon Sep 17 00:00:00 2001

From: Yoshihiro Shimoda yoshihiro.shimoda.uh@renesas.com Date: Mon, 22 Jul 2019 19:58:25 +0900 Subject: usb-storage: Add a limitation for blk_queue_max_hw_sectors()

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") Cc: stable stable@vger.kernel.org Signed-off-by: Yoshihiro Shimoda yoshihiro.shimoda.uh@renesas.com Acked-by: Alan Stern stern@rowland.harvard.edu Reviewed-by: Christoph Hellwig hch@lst.de Link: https://lore.kernel.org/r/1563793105-20597-1-git-send-email-yoshihiro.shimod... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- 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 30790240aec6..05b80211290d 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, @@ -128,6 +131,14 @@ static int slave_configure(struct scsi_device *sdev) blk_queue_max_hw_sectors(sdev->request_queue, 2048); }

+ /* + * 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