• Artem Bityutskiy's avatar
    UBI: preserve corrupted PEBs · 5fc01ab6
    Artem Bityutskiy authored
    Currently UBI erases all corrupted eraseblocks, irrespectively of the nature
    of corruption: corruption due to power cuts and non-power cut corruption.
    The former case is OK, but the latter is not, because UBI may destroy
    potentially important data.
    
    With this patch, during scanning, when UBI hits a PEB with corrupted VID
    header, it checks whether this PEB contains only 0xFF data. If yes, it is
    safe to erase this PEB and it is put to the 'erase' list. If not, this may
    be important data and it is better to avoid erasing this PEB. Instead,
    UBI puts it to the corr list and moves out of the pool of available PEB.
    IOW, UBI preserves this PEB.
    
    Such corrupted PEB lessen the amount of available PEBs. So the more of them
    we accumulate, the less PEBs are available. The maximum amount of non-power
    cut corrupted PEBs is 8.
    
    This patch is a response to UBIFS problem where reporter
    (Matthew L. Creech <mlcreech@gmail.com>) observes that UBIFS index points
    to an unmapped LEB. The theory is that corresponding PEB somehow got
    corrupted and UBI wiped it. This patch (actually a series of patches)
    tries to make sure such PEBs are preserved - this would make it is easier
    to analyze the corruption.
    Signed-off-by: default avatarArtem Bityutskiy <Artem.Bityutskiy@nokia.com>
    5fc01ab6
ubi.h 23.9 KB