• Alan Stern's avatar
    usb-storage: Revert commit 747668db ("usb-storage: Set virt_boundary_mask... · 9a976949
    Alan Stern authored
    usb-storage: Revert commit 747668db ("usb-storage: Set virt_boundary_mask to avoid SG overflows")
    
    Commit 747668db ("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
    09324d32 ("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 ea44d190 ("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 747668db.
    Reported-and-tested-by: default avatarPiergiorgio Sartor <piergiorgio.sartor@nexgo.de>
    Link: https://marc.info/?l=linux-usb&m=157134199501202&w=2Signed-off-by: default avatarAlan Stern <stern@rowland.harvard.edu>
    CC: Seth Bollinger <Seth.Bollinger@digi.com>
    CC: <stable@vger.kernel.org>
    Fixes: 747668db ("usb-storage: Set virt_boundary_mask to avoid SG overflows")
    Acked-by: default avatarChristoph Hellwig <hch@lst.de>
    Link: https://lore.kernel.org/r/Pine.LNX.4.44L0.1910211145520.1673-100000@iolanthe.rowland.orgSigned-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    9a976949
scsiglue.c 19.8 KB