linux-kernel - Re: [PATCH] ethernet: mlx4: Delete an error message for a failed memory allocation in five functions

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Message-ID: <20180103160316.GB11348@ziepe.ca>
Date:   Wed, 3 Jan 2018 09:03:16 -0700
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Tariq Toukan <tariqt@...lanox.com>
Cc:     Julia Lawall <julia.lawall@...6.fr>,
        SF Markus Elfring <elfring@...rs.sourceforge.net>,
        linux-rdma@...r.kernel.org, netdev@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] ethernet: mlx4: Delete an error message for a failed
 memory allocation in five functions

On Wed, Jan 03, 2018 at 01:24:59PM +0200, Tariq Toukan wrote:

> >Strings take up space.  Since there is a backtrace on an out of memory
> >problem, if the string does not provide any more information than the
> >position of the call, then there is not much added value.  I don't know
> >what was the string in this case.  If it provides some additional
> >information, then it would be reasonable to keep it.
> 
> I don't really accept this claim...

The standard we are moving to is to rely on the backtrace print for
debugging. It is so huge it is unlikely a single print from the driver
will make much difference to the user's view.

Most users think backtrace == oops == bug report.

> In addition, some out-of-memory errors are recoverable, even though their
> backtrace is also printed. For example, in function mlx4_en_create_cq
> (appears in patch) we have a first allocation attempt (kzalloc_node) and a
> fallback (kzalloc).

Please send a patch fixing this as other have suggested, it is clearly
a bug.

Jason