From: Theodore Tso <tytso@mit.edu>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
Peter Zijlstra <peterz@infradead.org>,
Frederic Weisbecker <fweisbec@gmail.com>,
Arjan van de Ven <arjan@infradead.org>,
Pekka Paalanen <pq@iki.fi>,
Arnaldo Carvalho de Melo <acme@redhat.com>,
"H. Peter Anvin" <hpa@zytor.com>,
Mathieu Desnoyers <compudj@krystal.dyndns.org>,
Martin Bligh <mbligh@google.com>,
"Frank Ch. Eigler" <fche@redhat.com>,
Tom Zanussi <tzanussi@gmail.com>,
Masami Hiramatsu <mhiramat@redhat.com>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
Jason Baron <jbaron@redhat.com>,
Christoph Hellwig <hch@infradead.org>,
Jiaying Zhang <jiayingz@google.com>,
Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>,
mrubin@google.com, md@google.com,
Steven Rostedt <srostedt@redhat.com>
Subject: Re: [PATCH 5/5] tracing: add binary buffer files for use with splice
Date: Tue, 3 Mar 2009 23:46:14 -0500 [thread overview]
Message-ID: <20090304044614.GL32284@mit.edu> (raw)
In-Reply-To: <alpine.DEB.2.00.0903032242180.6862@gandalf.stny.rr.com>
On Tue, Mar 03, 2009 at 10:43:16PM -0500, 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.
>
What is normally done in this case if buf is within the addressable
space, but buf+x is not, where x < len, then read(fd, buf, len) will
fill copy as many characters it can into buf until it runs out of
valid addres space, and then return that count as a partial read.
- Ted
next prev parent reply other threads:[~2009-03-04 4:46 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-04 2:49 [PATCH 0/5] [RFC] binary reading of ftrace ring buffers Steven Rostedt
2009-03-04 2:49 ` [PATCH 1/5] ring-buffer: reset write field for ring_buffer_read_page Steven Rostedt
2009-03-04 2:49 ` [PATCH 2/5] ring-buffer: fix ring_buffer_read_page Steven Rostedt
2009-03-04 2:49 ` [PATCH 3/5] ring-buffer: replace sizeof of event header with offsetof Steven Rostedt
2009-03-04 2:49 ` [PATCH 4/5] ring-buffer: make ring_buffer_read_page read from start on partial page Steven Rostedt
2009-03-04 2:49 ` [PATCH 5/5] tracing: add binary buffer files for use with splice Steven Rostedt
2009-03-04 3:35 ` Andrew Morton
2009-03-04 3:43 ` Steven Rostedt
2009-03-04 4:38 ` H. Peter Anvin
2009-03-04 4:45 ` Steven Rostedt
2009-03-04 4:46 ` Theodore Tso [this message]
2009-03-04 4:49 ` Steven Rostedt
2009-03-04 5:07 ` [PATCH] fs: make simple_read_from_buffer conventional Steven Rostedt
2009-03-04 10:12 ` Ingo Molnar
2009-03-04 3:01 ` [PATCH 0/5] [RFC] binary reading of ftrace ring buffers Steven Rostedt
2009-03-04 3:23 ` Steven Rostedt
2009-03-04 10:26 ` Ingo Molnar
2009-03-04 14:51 ` Steven Rostedt
2009-03-04 22:47 ` Ingo Oeser
2009-03-04 15:39 ` Mathieu Desnoyers
2009-03-04 17:00 ` Mathieu Desnoyers
2009-03-04 17:19 ` Peter Zijlstra
2009-03-06 16:59 ` Steven Rostedt
2009-03-06 19:10 ` Mathieu Desnoyers
2009-03-06 23:28 ` Jiaying Zhang
2009-03-08 19:21 ` Ingo Molnar
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