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    SubjectRe: data corruption: revalidating a (removable) hdd/flash on re-insert
    On Fri 2008-10-31 17:10:26, Kay Sievers wrote:
    > On Fri, Oct 31, 2008 at 16:38, Michael Tokarev <> wrote:
    > > To make a long story short: is there a way to force kernel
    > > to re-validate a replaced usb-connected hard drive (or a
    > > flash) *automatically*?
    > >
    > > Because right now, the kernel does not see that the drive
    > > has been replaced, and uses *some* old cached values, which
    > > results in random data corruption here and there, and other
    > > similar odd things.
    > Maybe your card reader is broken. I can not reproduce this with any of
    > the many readers I have. Usually a media change results in media
    > revalidation with the next access to the device. You can easily
    > reproduce that:
    > Insert the media, and force a validation:
    > $ touch /dev/sdb
    > Start logging of the kernel uevents to the console:
    > $ udevadm monitor --kernel &
    > Access the device:
    > $ touch /dev/sdb
    > Nothing should happen, as the reader/kernel knows it is still valid.
    > Now remove the media and insert it immediately again.
    > Access the device:
    > $ touch /dev/sdb
    > UEVENT[1225468868.803950] change
    > /devices/pci0000:00/0000:00:1d.7/usb5/5-2/5-2:1.0/host8/target8:0:0/8:0:0:0
    > (scsi)
    > and you see the reader told to kernel (scsi unit attention) to
    > revalidate the device.
    > These events happen only when the device is accessed. That's why
    > distros poll removable devices for media changes.
    > Every access to removable media is guarded by this revalidation check.
    > If you don't see these events, you should not trust this reader, and
    > at least never change the media while it is connected.

    This is rather nasty data-corrupter. Could we at least blacklist
    broken device, and force revalidation on each close or something like

    (cesky, pictures)

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