On Thu, Sep 7, 2017 at 8:13 AM, Shaohua Li [off-list ref] wrote:

From: Shaohua Li <redacted>

We don't know if fallocate really supports FALLOC_FL_PUNCH_HOLE till
fallocate is called. If it doesn't support, loop will return -EOPNOTSUPP
and we see a lot of error message printed by blk_update_request. Failure
for discard IO isn't a big problem, so we just return 0 in loop which
will suppress the IO error message.

Setting RQF_QUIET for discard IO should be more clean for suppressing error,
and upper layer can get the failure notification too.

-- 
Ming Lei