Messages in this thread |  | | Date | Fri, 10 Apr 2015 17:11:40 +0300 | From | Alexey Dobriyan <> | Subject | Re: [PATCH] fs/proc: allow larger /proc/<pid>/cmdline output |
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On Fri, Apr 10, 2015 at 08:18:38AM -0400, Jarod Wilson wrote: > On Thu, Apr 09, 2015 at 09:12:00PM -0700, Andrew Morton wrote: > > On Thu, 9 Apr 2015 23:59:02 -0400 Jarod Wilson <jarod@redhat.com> wrote: > > > > > There are people who run java. Sometimes, when it misbehaves, they try to > > > figure out what's going on by dumping /proc/<pid>/cmdline, but the length > > > of that output is currently capped by PAGE_SIZE (so x86_64's 4k, in most > > > cases), and sometimes, java command lines are longer than 4k characters. > > > > > > This change allows the user to request a larger max length, up to 4x > > > PAGE_SIZE, but the default out-of-the-box setting should keep things the > > > same as they ever were. The 4x maximum is somewhat arbitrary, but seemed > > > like it should be more than enough, because really, if you have more than > > > 16k characters on your command line, you're probably doing it wrong... > > > > > > I've tested this lightly with non-java shell commands with really long > > > parameters, and things are perfectly stable after several hundred > > > iterations of exercising things on a system booted with both > > > proc_pid_maxlen=8192 and 16384. I wouldn't call my testing exhaustive, > > > and I may not have considered something that will blow up horribly here, > > > so comments and clues welcomed. > > > > > > Using single_open_size() looked less messy than giving proc_pid_cmdline() > > > its own .start op that would allow multiple buffers. > > > > > > Note: I've only added this extended sizing for /proc/<pid>/cmdline output, > > > rather than for all /proc/<pid>/foo elements, thinking that nothing else > > > should ever really be that long, but anything that is can simply switch > > > from using the ONE() macro to the ONE_SIZE() macro. > > > > Why have an upper limit at all? > > Just trying to be conservative and keep people from doing anything too > insane, but I didn't really have any particularly good reason beyond that > for capping it. I'll remove the upper bound next iteration.
There is no need for next iteration. Andrew has been ignoring real fix for more than a month now!
Alexey
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