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SubjectRe: USB disk speed regression WD Elements - with bisect result 22547c4cc4fe20698a6a85a55b8788859134b8e4
On Mon, 24 Jul 2017, Zdenek Kabelac wrote:

> Hi
>
> I've problem with my USB storage devices: WD Elements 1TB.
> (Bus 004 Device 002: ID 1058:10a8 Western Digital Technologies, Inc. Elements
> Portable (WDBUZG))
>
>
> After kernel >4.9 when disk is attached via cable it has very low speed
> (less then 1MB/s).
>
> It can run at full speed (>22MB/s) when the Linux kernel is fully rebooted (so
> disk is attached during the reboot of Lenovo T61, C2D, Fedora Rawhide).
>
> However when >4.9 kernel is running and disk is just attached it's very slow.
>
> I've played a bisect game - and the clean result has been:
>
> 22547c4cc4fe20698a6a85a55b8788859134b8e4
>
> When I just revert this patch with 4.13-rc1 - it's again running with full
> speed even when disk is attached (thus no reboot is needed for full speed).
>
>
> So while I've no idea what 22547c4cc4fe20698... is doing, it seems to have
> some unpleasant side-effect on regular USB devices.
>
> So what else is needed to get this properly working ?
> (assuming plain revert of 22547c4cc4fe20698 is unwanted).
>
> What more info can I provide to get this storage 'normally' usable without
> rebooting the machine.

Please post the dmesg logs showing what happens when the disk is
first attached and operates slowly, and what happens when the disk is
attached following a reboot and operates normally.

Alan Stern

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