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linux/drivers/usb/storage
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Alan Stern 1186f86a71 UAS: Revert commit 3ae62a4209 ("UAS: fix alignment of scatter/gather segments") 
Commit 3ae62a4209 ("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 09324d32d2 ("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 ea44d19076 ("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 3ae62a4209.

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: 3ae62a4209 ("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>
2019-10-28 17:53:39 +01:00
..
alauda.c usb-storage: export symbols in USB_STORAGE namespace 2019-09-10 10:30:57 +02:00
cypress_atacb.c usb-storage: export symbols in USB_STORAGE namespace 2019-09-10 10:30:57 +02:00
datafab.c usb-storage: export symbols in USB_STORAGE namespace 2019-09-10 10:30:57 +02:00
debug.c
debug.h
ene_ub6250.c usb-storage: export symbols in USB_STORAGE namespace 2019-09-10 10:30:57 +02:00
freecom.c usb-storage: export symbols in USB_STORAGE namespace 2019-09-10 10:30:57 +02:00
initializers.c
initializers.h
isd200.c Modules updates for v5.4 2019-09-22 10:34:46 -07:00
jumpshot.c usb-storage: export symbols in USB_STORAGE namespace 2019-09-10 10:30:57 +02:00
karma.c usb-storage: export symbols in USB_STORAGE namespace 2019-09-10 10:30:57 +02:00
Kconfig
Makefile usb-storage: export symbols in USB_STORAGE namespace 2019-09-10 10:30:57 +02:00
onetouch.c usb-storage: export symbols in USB_STORAGE namespace 2019-09-10 10:30:57 +02:00
option_ms.c
option_ms.h
protocol.c
protocol.h
realtek_cr.c usb-storage: export symbols in USB_STORAGE namespace 2019-09-10 10:30:57 +02:00
scsiglue.c usb-storage: Revert commit 747668dbc0 ("usb-storage: Set virt_boundary_mask to avoid SG overflows") 2019-10-28 17:52:44 +01:00
scsiglue.h
sddr09.c usb-storage: export symbols in USB_STORAGE namespace 2019-09-10 10:30:57 +02:00
sddr55.c usb-storage: export symbols in USB_STORAGE namespace 2019-09-10 10:30:57 +02:00
shuttle_usbat.c usb-storage: export symbols in USB_STORAGE namespace 2019-09-10 10:30:57 +02:00
sierra_ms.c
sierra_ms.h
transport.c
transport.h
uas-detect.h
uas.c UAS: Revert commit 3ae62a4209 ("UAS: fix alignment of scatter/gather segments") 2019-10-28 17:53:39 +01:00
unusual_alauda.h
unusual_cypress.h
unusual_datafab.h
unusual_devs.h
unusual_ene_ub6250.h
unusual_freecom.h
unusual_isd200.h
unusual_jumpshot.h
unusual_karma.h
unusual_onetouch.h
unusual_realtek.h
unusual_sddr09.h
unusual_sddr55.h
unusual_uas.h
unusual_usbat.h
usb.c
usb.h
usual-tables.c