From: Alan Stern <[email protected]>
commit 1186f86a71130a7635a20843e355bb880c7349b2 upstream.
Commit 3ae62a42090f ("UAS: fix alignment of scatter/gather segments"),
copying a similar commit for usb-storage, 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 the analogous change in usb-storage
interacted 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
in the uas driver. 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 head
off potential problems similar to those affecting usb-storage, this
patch reverts commit 3ae62a42090f.
Signed-off-by: Alan Stern <[email protected]>
CC: Oliver Neukum <[email protected]>
CC: <[email protected]>
Acked-by: Christoph Hellwig <[email protected]>
Fixes: 3ae62a42090f ("UAS: fix alignment of scatter/gather segments")
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
drivers/usb/storage/uas.c | 20 --------------------
1 file changed, 20 deletions(-)
--- a/drivers/usb/storage/uas.c
+++ b/drivers/usb/storage/uas.c
@@ -772,30 +772,10 @@ static int uas_slave_alloc(struct scsi_d
{
struct uas_dev_info *devinfo =
(struct uas_dev_info *)sdev->host->hostdata;
- int maxp;
sdev->hostdata = devinfo;
/*
- * We have two requirements here. We must satisfy the requirements
- * of the physical HC and the demands of the protocol, as we
- * definitely want no additional memory allocation in this path
- * ruling out using bounce buffers.
- *
- * For a transmission on USB to continue we must never send
- * a package that is smaller than maxpacket. Hence the length of each
- * scatterlist element except the last must be divisible by the
- * Bulk maxpacket value.
- * If the HC does not ensure that through SG,
- * the upper layer must do that. We must assume nothing
- * about the capabilities off the HC, so we use the most
- * pessimistic requirement.
- */
-
- maxp = usb_maxpacket(devinfo->udev, devinfo->data_in_pipe, 0);
- blk_queue_virt_boundary(sdev->request_queue, maxp - 1);
-
- /*
* The protocol has no requirements on alignment in the strict sense.
* Controllers may or may not have alignment restrictions.
* As this is not exported, we use an extremely conservative guess.
Am Montag, den 04.11.2019, 22:44 +0100 schrieb Greg Kroah-Hartman:
> From: Alan Stern <[email protected]>
>
> commit 1186f86a71130a7635a20843e355bb880c7349b2 upstream.
>
> Commit 3ae62a42090f ("UAS: fix alignment of scatter/gather segments"),
> copying a similar commit for usb-storage, attempted to solve a problem
> involving scatter-gather I/O and USB/IP by setting the
> virt_boundary_mask for mass-storage devices.
We have that in 4.4.x
> However, it now turns out that the analogous change in usb-storage
> interacted 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:
09324d32d2a0 I cannot find.
> 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
> in the uas driver. 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.
Neither can I find ea44d190764b.
It seems to me that, while the patch is necessary in upstream, in 4.4.x
it would break usbip.
Regards
Oliver