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SubjectRe: Page cache corruption with mount/unmount of USB with Fat file system
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Hi Ted,

>And I'll repeat the comments I made a few weeks ago. Last time you
>reported this, you included a dmesg output which included this:

> [ 413.607849] usb 2-1.1: USB disconnect, device number 12
> [ 414.022630] EXT4-fs error (device mmcblk0p20): ext4_readdir:227: inode
> #81827: block 328308: comm installd...

> Are you seeing the same thing? If so, the fundamental high level
issue is that the USB driver is reporting a device disconnect,
presumably of a USB device different from the one that you just
plugged in. Are you still seeing this?

The dmesg output that I attached earlier was when I saw the prints
after actually disconnecting the USB. I am pretty certain that USB
driver does not report any false disconnect. This issue occurs when I
connect the USBdrive on android tablet with USB mount support. This
issue may or may not occur the first time I hotplug the USB drive. It
might require couple of hotplug/hotunplug to see this issue.

Thank you,
Nilesh

On Thu, Mar 20, 2014 at 12:31 AM, <tytso@mit.edu> wrote:
> On Thu, Mar 20, 2014 at 12:05:44AM +0530, Nilesh More wrote:
>> Hi all,
>>
>> First of all sorry for the lengthy mail but I did not want to miss out
>> on any details.
>>
>> The following issue that I am reporting occurs when I plugin the USB
>> drive on android tablet with USB mount support. Please note that this
>> issue may or may not occur the first time I hotplug the USB drive. It
>> might require couple of hotplug/hotunplug to see this issue. If
>> anybody has/gets any clue about the possible root cause, please let me
>> know.
>
> And I'll repeat the comments I made a few weeks ago. Last time you
> reported this, you included a dmesg output which included this:
>
>> [ 413.607849] usb 2-1.1: USB disconnect, device number 12
>> [ 414.022630] EXT4-fs error (device mmcblk0p20): ext4_readdir:227: inode
>> #81827: block 328308: comm installd...
>
> Are you seeing the same thing? If so, the fundamental high level
> issue is that the USB driver is reporting a device disconnect,
> presumably of a USB device different from the one that you just
> plugged in. Are you still seeing this?
>
> If so, it's important if you want to root cause this issue to
> determine why the USB disconnect is happening, and not try to comment
> out the page invalidations which happens *after* the USB device is
> reported as disconnected.
>
> If I had to guess, it's probably some hardware issue where when you
> plug in a USB device that draws too much power, it's destablizing the
> USB bus and causing some other USB device to report a disconnect.
>
> - Ted


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