linux-kernel - Re: iov_iter

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Message-ID: <20170411211216.GH29622@ZenIV.linux.org.uk>
Date:   Tue, 11 Apr 2017 22:12:16 +0100
From:   Al Viro <viro@...IV.linux.org.uk>
To:     Dave Jones <davej@...emonkey.org.uk>,
        Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: iov_iter_pipe warning.

On Tue, Apr 11, 2017 at 04:53:36PM -0400, Dave Jones wrote:
>  > 		if (WARN_ON(pipe->nrbufs)) {
>  > 			printk(KERN_ERR "->splice_write = %p",
>  > 				sd->u.file->f_op->splice_write);
>  > 		}
>  > 	}
> 
> Ah, missed adding this 2nd WARN_ON.

Good - it means that we don't have to chase memory corruption yet.  That
smells like some ->splice_write() claiming it has copied more than it
has drained from the pipe.

> I'll turn it back off, and retry with the missing WARN from above added.

Please, do.  And it would be nice if you printed sd->u.file->f_op as well
(in the same printk).