From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Elder Subject: [PATCH 3/4] rbd: add a warning in bio_chain_clone_range() Date: Thu, 01 Nov 2012 10:26:42 -0500 Message-ID: <509294B2.6090705@inktank.com> References: <50929419.6020302@inktank.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from mail-ia0-f174.google.com ([209.85.210.174]:42446 "EHLO mail-ia0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935828Ab2KAP0q (ORCPT ); Thu, 1 Nov 2012 11:26:46 -0400 Received: by mail-ia0-f174.google.com with SMTP id y32so1983034iag.19 for ; Thu, 01 Nov 2012 08:26:46 -0700 (PDT) In-Reply-To: <50929419.6020302@inktank.com> Sender: ceph-devel-owner@vger.kernel.org List-ID: To: ceph-devel@vger.kernel.org Add a warning in bio_chain_clone_range() to help a user determine what exactly might have led to a failure. There is only one; please say something if you disagree with the following reasoning. There are three places this can return abnormally: - Initially, if there is nothing to clone. It turns out that right now this cannot happen anyway. The test is in place because the code below it doesn't work if those conditions don't hold. As such they could be assertions but since I can return a null to indicate an error I just do that instead. I have not added a warning here because it won't happen. - While processing bio's, if none remain but there are supposed to be more bytes to clone. Here I have added a warning. - If bio_clone_range() returns a null pointer. That function will have already produced a warning (at least the first time, via WARN_ON_ONCE()) to distinguish the cause of the error. The only exception is memory exhaustion, and I'd rather not pepper the code with warnings in all those spots. So no warning is added in that place. Signed-off-by: Alex Elder --- drivers/block/rbd.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c index de1d3b1..3ab3970 100644 --- a/drivers/block/rbd.c +++ b/drivers/block/rbd.c @@ -995,8 +995,10 @@ static struct bio *bio_chain_clone_range(struct bio **bio_src, unsigned int bi_size; struct bio *bio; - if (!bi) + if (!bi) { + rbd_warn(NULL, "bio_chain exhausted with %u left", len); goto out_err; /* EINVAL; ran out of bio's */ + } bi_size = min_t(unsigned int, bi->bi_size - off, len); bio = bio_clone_range(bi, off, bi_size, gfpmask); if (!bio) -- 1.7.9.5