Re: [PATCH] don't use mmap() to hash files

From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Feb 14, 2010, 18:10 UTC
Message-ID: <alpine.DEB.1.00.1002141908150.20986@pacific.mpi-cbg.de>
In-Reply-To: <20100214024259.GB9704@dpotapov.dyndns.org>

Hi,

On Sun, 14 Feb 2010, Dmitry Potapov wrote:

Show 10 quoted lines

> On Sun, Feb 14, 2010 at 02:53:58AM +0100, Johannes Schindelin wrote:
> > On Sun, 14 Feb 2010, Dmitry Potapov wrote:
> > 
> > > +	if (strbuf_read(&sbuf, fd, 4096) >= 0)
> > 
> > How certain are you at this point that all of fd's contents fit into 
> > your memory?
> 
> You can't be sure... In fact, we know mmap() also may fail for huge
> files, so can strbuf_read().

That's comparing oranges to apples. In one case, the address space runs out, in the other the available memory. The latter is much more likely.

Show 7 quoted lines

> > And even if you could be certain, a hint is missing that 
> > strbuf_read(), its name notwithstanding, does not read NUL-terminated 
> > strings. Oh, and the size is just a hint for the initial size, and it 
> > reads until EOF. That has to be said in the commit message.
> 
> I did not add _any_ new code, including the above line. It was there
> before my patch.

But that explanation does not answer my question, does it? And my question was not unreasonable to ask, was it?

Ciao, Dscho