Re: [PATCH 5/5] tracing: add binary buffer files for use withsplice

[Steven Rostedt]

On Tue, 3 Mar 2009, H. Peter Anvin wrote:

> Steven Rostedt wrote:
> > > Conventionally a read() system call will return the number of bytes
> > > copied, and will only return -EFOO if the number of bytes copied was
> > > zero.
> > > 
> > > Lots of parts of the kernel break this, but it's usually device drivers
> > > and scruffy pseudo files, in which case a partial file read doesn't
> > > make much sense.  This doesn't make the broken behaviour right, but at
> > > least we have a bit of a weaselly excuse in that case.
> > 
> > I just went by the read man page:
> > 
> >        EFAULT buf is outside your accessible address space.
> 
> Yes, and that is the correct value if no bytes were copied.

Yuck. IMHO I rather have a read return a failure to my user app if I'm 
trying to write to more than I allocated. I guess I can change it, but it 
just seems to be hiding a bug in a user app.

-- Steve

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