| Message ID | Pine.LNX.4.44L0.1910211145520.1673-100000@iolanthe.rowland.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | usb-storage: Revert commit 747668dbc061 ("usb-storage: Set virt_boundary_mask to avoid SG overflows") | expand |
On Mon, Oct 21, 2019 at 11:48:06AM -0400, Alan Stern wrote: > There is no longer any reason to keep the virt_boundary_mask setting > for usb-storage. It was needed in the first place only for handling > devices with a block size smaller than the maxpacket size and where > the host controller was not capable of fully general scatter-gather > operation (that is, able to merge two SG segments into a single USB > packet). But: > > High-speed or slower connections never use a bulk maxpacket > value larger than 512; > > The SCSI layer does not handle block devices with a block size > smaller than 512 bytes; > > All the host controllers capable of SuperSpeed operation can > handle fully general SG; > > Since commit ea44d190764b ("usbip: Implement SG support to > vhci-hcd and stub driver") was merged, the USB/IP driver can > also handle SG. > > Therefore all supported device/controller combinations should be okay > with no need for any special virt_boundary_mask. So in order to fix > the swiotlb problem, this patch reverts commit 747668dbc061. That's great to know. The same should also apply to uas, shouldn't it? Otherwise: Acked-by: Christoph Hellwig <hch@lst.de>
On Wed, 23 Oct 2019, Christoph Hellwig wrote: > On Mon, Oct 21, 2019 at 11:48:06AM -0400, Alan Stern wrote: > > There is no longer any reason to keep the virt_boundary_mask setting > > for usb-storage. It was needed in the first place only for handling > > devices with a block size smaller than the maxpacket size and where > > the host controller was not capable of fully general scatter-gather > > operation (that is, able to merge two SG segments into a single USB > > packet). But: > > > > High-speed or slower connections never use a bulk maxpacket > > value larger than 512; > > > > The SCSI layer does not handle block devices with a block size > > smaller than 512 bytes; > > > > All the host controllers capable of SuperSpeed operation can > > handle fully general SG; > > > > Since commit ea44d190764b ("usbip: Implement SG support to > > vhci-hcd and stub driver") was merged, the USB/IP driver can > > also handle SG. > > > > Therefore all supported device/controller combinations should be okay > > with no need for any special virt_boundary_mask. So in order to fix > > the swiotlb problem, this patch reverts commit 747668dbc061. > > That's great to know. The same should also apply to uas, shouldn't > it? Ah, yes, excellent point -- I had forgotten about it. Additional patch coming up soon... Alan Stern > Otherwise: > > Acked-by: Christoph Hellwig <hch@lst.de>
Index: usb-devel/drivers/usb/storage/scsiglue.c =================================================================== --- usb-devel.orig/drivers/usb/storage/scsiglue.c +++ usb-devel/drivers/usb/storage/scsiglue.c @@ -68,7 +68,6 @@ static const char* host_info(struct Scsi static int slave_alloc (struct scsi_device *sdev) { struct us_data *us = host_to_us(sdev->host); - int maxp; /* * Set the INQUIRY transfer length to 36. We don't use any of @@ -78,15 +77,6 @@ static int slave_alloc (struct scsi_devi sdev->inquiry_len = 36; /* - * USB has unusual scatter-gather requirements: the length of each - * scatterlist element except the last must be divisible by the - * Bulk maxpacket value. Fortunately this value is always a - * power of 2. Inform the block layer about this requirement. - */ - maxp = usb_maxpacket(us->pusb_dev, us->recv_bulk_pipe, 0); - blk_queue_virt_boundary(sdev->request_queue, maxp - 1); - - /* * Some host controllers may have alignment requirements. * We'll play it safe by requiring 512-byte alignment always. */
Commit 747668dbc061 ("usb-storage: Set virt_boundary_mask to avoid SG overflows") attempted to solve a problem involving scatter-gather I/O and USB/IP by setting the virt_boundary_mask for mass-storage devices. However, it now turns out that this interacts badly with commit 09324d32d2a0 ("block: force an unlimited segment size on queues with a virt boundary"), which was added later. A typical error message is: ehci-pci 0000:00:13.2: swiotlb buffer is full (sz: 327680 bytes), total 32768 (slots), used 97 (slots) There is no longer any reason to keep the virt_boundary_mask setting for usb-storage. It was needed in the first place only for handling devices with a block size smaller than the maxpacket size and where the host controller was not capable of fully general scatter-gather operation (that is, able to merge two SG segments into a single USB packet). But: High-speed or slower connections never use a bulk maxpacket value larger than 512; The SCSI layer does not handle block devices with a block size smaller than 512 bytes; All the host controllers capable of SuperSpeed operation can handle fully general SG; Since commit ea44d190764b ("usbip: Implement SG support to vhci-hcd and stub driver") was merged, the USB/IP driver can also handle SG. Therefore all supported device/controller combinations should be okay with no need for any special virt_boundary_mask. So in order to fix the swiotlb problem, this patch reverts commit 747668dbc061. Reported-and-tested-by: Piergiorgio Sartor <piergiorgio.sartor@nexgo.de> Link: https://marc.info/?l=linux-usb&m=157134199501202&w=2 Signed-off-by: Alan Stern <stern@rowland.harvard.edu> CC: Seth Bollinger <Seth.Bollinger@digi.com> CC: <stable@vger.kernel.org> --- [as1922] drivers/usb/storage/scsiglue.c | 10 ---------- 1 file changed, 10 deletions(-)