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    xfs: remote attribute overwrite causes transaction overrun · 8275cdd0
    Dave Chinner 提交于
    Commit e461fcb1 ("xfs: remote attribute lookups require the value
    length") passes the remote attribute length in the xfs_da_args
    structure on lookup so that CRC calculations and validity checking
    can be performed correctly by related code. This, unfortunately has
    the side effect of changing the args->valuelen parameter in cases
    where it shouldn't.
    
    That is, when we replace a remote attribute, the incoming
    replacement stores the value and length in args->value and
    args->valuelen, but then the lookup which finds the existing remote
    attribute overwrites args->valuelen with the length of the remote
    attribute being replaced. Hence when we go to create the new
    attribute, we create it of the size of the existing remote
    attribute, not the size it is supposed to be. When the new attribute
    is much smaller than the old attribute, this results in a
    transaction overrun and an ASSERT() failure on a debug kernel:
    
    XFS: Assertion failed: tp->t_blk_res_used <= tp->t_blk_res, file: fs/xfs/xfs_trans.c, line: 331
    
    Fix this by keeping the remote attribute value length separate to
    the attribute value length in the xfs_da_args structure. The enables
    us to pass the length of the remote attribute to be removed without
    overwriting the new attribute's length.
    
    Also, ensure that when we save remote block contexts for a later
    rename we zero the original state variables so that we don't confuse
    the state of the attribute to be removes with the state of the new
    attribute that we just added. [Spotted by Brain Foster.]
    Signed-off-by: NDave Chinner <dchinner@redhat.com>
    Reviewed-by: NBrian Foster <bfoster@redhat.com>
    Signed-off-by: NDave Chinner <david@fromorbit.com>
    8275cdd0
xfs_attr_list.c 16.3 KB