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    SubjectRe: [PATCH 1/1] scsi: retrieve cache mode using ATA_16 if normal routine fails
    On Mon, 2011-12-12 at 16:48 +0530, Amit Sahrawat wrote:
    > It has been observed that a number of USB HDD's do not respond correctly
    > to SCSI mode sense command(retrieve caching pages) which results in their
    > Write Cache being discarded by queue requests i.e., WCE if left set to
    > '0'(disabled).
    > This results in a number of Filesystem corruptions, when the device
    > is unplugged abruptly.

    Um, how would knowing the caching type correctly help? If you surprise
    unplug the device, we can't send a flush to it anyway ...

    > So, in order to identify the devices correctly - give it
    > a last try using ATA_16 after failure from normal routine.
    > Introduce a mechanism to store write-cache type using /sys/class/
    > interface, so that the normal code continues to function without errors.
    > Signed-off-by: Amit Sahrawat <>
    > Signed-off-by: Nam-Jae Jeon <>

    This whole patch looks like a layering violation. Why not just update
    the SAT layer to translate the MODE SENSE correctly?


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