git.ipfire.org Git - thirdparty/kernel/stable-queue.git/blob

   1 From 9a976949613132977098fc49510b46fa8678d864 Mon Sep 17 00:00:00 2001
   2 From: Alan Stern <stern@rowland.harvard.edu>
   3 Date: Mon, 21 Oct 2019 11:48:06 -0400
   4 Subject: usb-storage: Revert commit 747668dbc061 ("usb-storage: Set virt_boundary_mask to avoid SG overflows")
   5
   6 From: Alan Stern <stern@rowland.harvard.edu>
   7
   8 commit 9a976949613132977098fc49510b46fa8678d864 upstream.
   9
  10 Commit 747668dbc061 ("usb-storage: Set virt_boundary_mask to avoid SG
  11 overflows") attempted to solve a problem involving scatter-gather I/O
  12 and USB/IP by setting the virt_boundary_mask for mass-storage devices.
  13
  14 However, it now turns out that this interacts badly with commit
  15 09324d32d2a0 ("block: force an unlimited segment size on queues with a
  16 virt boundary"), which was added later.  A typical error message is:
  17
  18         ehci-pci 0000:00:13.2: swiotlb buffer is full (sz: 327680 bytes),
  19         total 32768 (slots), used 97 (slots)
  20
  21 There is no longer any reason to keep the virt_boundary_mask setting
  22 for usb-storage.  It was needed in the first place only for handling
  23 devices with a block size smaller than the maxpacket size and where
  24 the host controller was not capable of fully general scatter-gather
  25 operation (that is, able to merge two SG segments into a single USB
  26 packet).  But:
  27
  28         High-speed or slower connections never use a bulk maxpacket
  29         value larger than 512;
  30
  31         The SCSI layer does not handle block devices with a block size
  32         smaller than 512 bytes;
  33
  34         All the host controllers capable of SuperSpeed operation can
  35         handle fully general SG;
  36
  37         Since commit ea44d190764b ("usbip: Implement SG support to
  38         vhci-hcd and stub driver") was merged, the USB/IP driver can
  39         also handle SG.
  40
  41 Therefore all supported device/controller combinations should be okay
  42 with no need for any special virt_boundary_mask.  So in order to fix
  43 the swiotlb problem, this patch reverts commit 747668dbc061.
  44
  45 Reported-and-tested-by: Piergiorgio Sartor <piergiorgio.sartor@nexgo.de>
  46 Link: https://marc.info/?l=linux-usb&m=157134199501202&w=2
  47 Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
  48 CC: Seth Bollinger <Seth.Bollinger@digi.com>
  49 CC: <stable@vger.kernel.org>
  50 Fixes: 747668dbc061 ("usb-storage: Set virt_boundary_mask to avoid SG overflows")
  51 Acked-by: Christoph Hellwig <hch@lst.de>
  52 Link: https://lore.kernel.org/r/Pine.LNX.4.44L0.1910211145520.1673-100000@iolanthe.rowland.org
  53 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  54
  55 ---
  56  drivers/usb/storage/scsiglue.c |   10 ----------
  57  1 file changed, 10 deletions(-)
  58
  59 --- a/drivers/usb/storage/scsiglue.c
  60 +++ b/drivers/usb/storage/scsiglue.c
  61 @@ -67,7 +67,6 @@ static const char* host_info(struct Scsi
  62  static int slave_alloc (struct scsi_device *sdev)
  63  {
  64         struct us_data *us = host_to_us(sdev->host);
  65 -       int maxp;
  66
  67         /*
  68          * Set the INQUIRY transfer length to 36.  We don't use any of
  69 @@ -77,15 +76,6 @@ static int slave_alloc (struct scsi_devi
  70         sdev->inquiry_len = 36;
  71
  72         /*
  73 -        * USB has unusual scatter-gather requirements: the length of each
  74 -        * scatterlist element except the last must be divisible by the
  75 -        * Bulk maxpacket value.  Fortunately this value is always a
  76 -        * power of 2.  Inform the block layer about this requirement.
  77 -        */
  78 -       maxp = usb_maxpacket(us->pusb_dev, us->recv_bulk_pipe, 0);
  79 -       blk_queue_virt_boundary(sdev->request_queue, maxp - 1);
  80 -
  81 -       /*
  82          * Some host controllers may have alignment requirements.
  83          * We'll play it safe by requiring 512-byte alignment always.
  84          */