releases/5.0.15/usb-storage-set-virt_boundary_mask-to-avoid-sg-overflows.patch

   1 From 747668dbc061b3e62bc1982767a3a1f9815fcf0e Mon Sep 17 00:00:00 2001
   2 From: Alan Stern <stern@rowland.harvard.edu>
   3 Date: Mon, 15 Apr 2019 13:19:25 -0400
   4 Subject: usb-storage: Set virt_boundary_mask to avoid SG overflows
   5
   6 From: Alan Stern <stern@rowland.harvard.edu>
   7
   8 commit 747668dbc061b3e62bc1982767a3a1f9815fcf0e upstream.
   9
  10 The USB subsystem has always had an unusual requirement for its
  11 scatter-gather transfers: Each element in the scatterlist (except the
  12 last one) must have a length divisible by the bulk maxpacket size.
  13 This is a particular issue for USB mass storage, which uses SG lists
  14 created by the block layer rather than setting up its own.
  15
  16 So far we have scraped by okay because most devices have a logical
  17 block size of 512 bytes or larger, and the bulk maxpacket sizes for
  18 USB 2 and below are all <= 512.  However, USB 3 has a bulk maxpacket
  19 size of 1024.  Since the xhci-hcd driver includes native SG support,
  20 this hasn't mattered much.  But now people are trying to use USB-3
  21 mass storage devices with USBIP, and the vhci-hcd driver currently
  22 does not have full SG support.
  23
  24 The result is an overflow error, when the driver attempts to implement
  25 an SG transfer of 63 512-byte blocks as a single
  26 3584-byte (7 blocks) transfer followed by seven 4096-byte (8 blocks)
  27 transfers.  The device instead sends 31 1024-byte packets followed by
  28 a 512-byte packet, and this overruns the first SG buffer.
  29
  30 Ideally this would be fixed by adding better SG support to vhci-hcd.
  31 But for now it appears we can work around the problem by
  32 asking the block layer to respect the maxpacket limitation, through
  33 the use of the virt_boundary_mask.
  34
  35 Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
  36 Reported-by: Seth Bollinger <Seth.Bollinger@digi.com>
  37 Tested-by: Seth Bollinger <Seth.Bollinger@digi.com>
  38 CC: Ming Lei <tom.leiming@gmail.com>
  39 Cc: stable <stable@vger.kernel.org>
  40 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  41
  42 ---
  43  drivers/usb/storage/scsiglue.c |   26 ++++++++++++--------------
  44  1 file changed, 12 insertions(+), 14 deletions(-)
  45
  46 --- a/drivers/usb/storage/scsiglue.c
  47 +++ b/drivers/usb/storage/scsiglue.c
  48 @@ -65,6 +65,7 @@ static const char* host_info(struct Scsi
  49  static int slave_alloc (struct scsi_device *sdev)
  50  {
  51         struct us_data *us = host_to_us(sdev->host);
  52 +       int maxp;
  53
  54         /*
  55          * Set the INQUIRY transfer length to 36.  We don't use any of
  56 @@ -74,20 +75,17 @@ static int slave_alloc (struct scsi_devi
  57         sdev->inquiry_len = 36;
  58
  59         /*
  60 -        * USB has unusual DMA-alignment requirements: Although the
  61 -        * starting address of each scatter-gather element doesn't matter,
  62 -        * the length of each element except the last must be divisible
  63 -        * by the Bulk maxpacket value.  There's currently no way to
  64 -        * express this by block-layer constraints, so we'll cop out
  65 -        * and simply require addresses to be aligned at 512-byte
  66 -        * boundaries.  This is okay since most block I/O involves
  67 -        * hardware sectors that are multiples of 512 bytes in length,
  68 -        * and since host controllers up through USB 2.0 have maxpacket
  69 -        * values no larger than 512.
  70 -        *
  71 -        * But it doesn't suffice for Wireless USB, where Bulk maxpacket
  72 -        * values can be as large as 2048.  To make that work properly
  73 -        * will require changes to the block layer.
  74 +        * USB has unusual scatter-gather requirements: the length of each
  75 +        * scatterlist element except the last must be divisible by the
  76 +        * Bulk maxpacket value.  Fortunately this value is always a
  77 +        * power of 2.  Inform the block layer about this requirement.
  78 +        */
  79 +       maxp = usb_maxpacket(us->pusb_dev, us->recv_bulk_pipe, 0);
  80 +       blk_queue_virt_boundary(sdev->request_queue, maxp - 1);
  81 +
  82 +       /*
  83 +        * Some host controllers may have alignment requirements.
  84 +        * We'll play it safe by requiring 512-byte alignment always.
  85          */
  86         blk_queue_update_dma_alignment(sdev->request_queue, (512 - 1));
  87