diff options
| author | Alan Stern <stern@rowland.harvard.edu> | 2019-10-23 11:34:33 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-11-06 12:43:28 +0100 |
| commit | 0b5a7e7d8d85160d874ce382ba690a41a158ecc7 (patch) | |
| tree | 1cff2203992032ebbb0ded5bb07ab879e316208f /drivers/usb | |
| parent | 9d7336ac28f7a169f327fe6a30debbc01682b366 (diff) | |
UAS: Revert commit 3ae62a42090f ("UAS: fix alignment of scatter/gather segments")
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 <stern@rowland.harvard.edu>
CC: Oliver Neukum <oneukum@suse.com>
CC: <stable@vger.kernel.org>
Acked-by: Christoph Hellwig <hch@lst.de>
Fixes: 3ae62a42090f ("UAS: fix alignment of scatter/gather segments")
Link: https://lore.kernel.org/r/Pine.LNX.4.44L0.1910231132470.1878-100000@iolanthe.rowland.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/usb')
| -rw-r--r-- | drivers/usb/storage/uas.c | 20 |
1 files changed, 0 insertions, 20 deletions
diff --git a/drivers/usb/storage/uas.c b/drivers/usb/storage/uas.c index 21c8925a4116..1e62f2134b3a 100644 --- a/drivers/usb/storage/uas.c +++ b/drivers/usb/storage/uas.c @@ -796,30 +796,10 @@ static int uas_slave_alloc(struct scsi_device *sdev) { 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. |