• NeilBrown's avatar
    md: flush writes before starting a recovery. · 74d31de6
    NeilBrown authored
    commit 133d4527 upstream.
    
    When we write to a degraded array which has a bitmap, we
    make sure the relevant bit in the bitmap remains set when
    the write completes (so a 're-add' can quickly rebuilt a
    temporarily-missing device).
    
    If, immediately after such a write starts, we incorporate a spare,
    commence recovery, and skip over the region where the write is
    happening (because the 'needs recovery' flag isn't set yet),
    then that write will not get to the new device.
    
    Once the recovery finishes the new device will be trusted, but will
    have incorrect data, leading to possible corruption.
    
    We cannot set the 'needs recovery' flag when we start the write as we
    do not know easily if the write will be "degraded" or not.  That
    depends on details of the particular raid level and particular write
    request.
    
    This patch fixes a corruption issue of long standing and so it
    suitable for any -stable kernel.  It applied correctly to 3.0 at
    least and will minor editing to earlier kernels.
    Reported-by: default avatarBill <billstuff2001@sbcglobal.net>
    Tested-by: default avatarBill <billstuff2001@sbcglobal.net>
    Link: http://lkml.kernel.org/r/53A518BB.60709@sbcglobal.netSigned-off-by: default avatarNeilBrown <neilb@suse.de>
    Signed-off-by: default avatarBen Hutchings <ben@decadent.org.uk>
    74d31de6
md.c 215 KB