From: Christoph Hellwig <hch@lst.de>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: Greg KH <greg@kroah.com>, Oliver Neukum <oneukum@suse.com>,
Piergiorgio Sartor <piergiorgio.sartor@nexgo.de>,
Seth Bollinger <Seth.Bollinger@digi.com>,
Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
USB list <linux-usb@vger.kernel.org>
Subject: Re: [PATCH] UAS: Revert commit 3ae62a42090f ("UAS: fix alignment of scatter/gather segments")
Date: Thu, 24 Oct 2019 03:10:59 +0200 [thread overview]
Message-ID: <20191024011059.GB5067@lst.de> (raw)
In-Reply-To: <Pine.LNX.4.44L0.1910231132470.1878-100000@iolanthe.rowland.org>
On Wed, Oct 23, 2019 at 11:34:33AM -0400, Alan Stern wrote:
> 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>
Looks good,
Acked-by: Christoph Hellwig <hch@lst.de>
prev parent reply other threads:[~2019-10-24 1:11 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-17 9:54 reeze while write on external usb 3.0 hard disk [Bug 204095] Piergiorgio Sartor
2019-08-19 14:14 ` Alan Stern
2019-08-20 7:23 ` Christoph Hellwig
2019-08-20 16:37 ` Piergiorgio Sartor
2019-08-26 17:38 ` Piergiorgio Sartor
2019-08-29 14:08 ` Christoph Hellwig
2019-09-25 17:07 ` Piergiorgio Sartor
2019-09-25 18:31 ` Alan Stern
2019-09-27 9:04 ` Peter Chen
2019-09-29 20:13 ` Piergiorgio Sartor
2019-09-30 1:01 ` Alan Stern
2019-09-30 18:25 ` Piergiorgio Sartor
2019-10-13 18:11 ` Piergiorgio Sartor
2019-10-16 17:01 ` Alan Stern
2019-10-17 17:53 ` Piergiorgio Sartor
2019-10-17 19:23 ` Alan Stern
2019-11-08 23:05 ` Piergiorgio Sartor
2019-10-21 15:48 ` [PATCH] usb-storage: Revert commit 747668dbc061 ("usb-storage: Set virt_boundary_mask to avoid SG overflows") Alan Stern
2019-10-23 1:53 ` Christoph Hellwig
2019-10-23 14:12 ` Alan Stern
2019-10-23 15:34 ` [PATCH] UAS: Revert commit 3ae62a42090f ("UAS: fix alignment of scatter/gather segments") Alan Stern
2019-10-24 1:10 ` Christoph Hellwig [this message]
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