On Wed, 11 Nov 2015 15:26:07 -0500 "J. Bruce Fields" <bfields@xxxxxxxxxxxx> wrote: > On Wed, Nov 11, 2015 at 11:49:20AM -0600, Eric W. Biederman wrote: > > > > Mandatory locking appears to be almost unused and buggy and there > > appears no real interest in doing anything with it. Since effectively > > no one uses the code and since the code is buggy let's allow it to be > > disabled at compile time. I would just suggest removing the code but > > undoubtedly that will break some piece of userspace code somewhere. > > > > For the distributions that don't care about this piece of code > > this gives a nice starting point to make mandatory locking go away. > > > > Cc: Benjamin Coddington <bcodding@xxxxxxxxxx> > > Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx> > > Cc: Jeff Layton <jeff.layton@xxxxxxxxxxxxxxx> > > Cc: J. Bruce Fields <bfields@xxxxxxxxxxxx> > > Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx> > > --- > > > > A piece of userspace software having problematic interactions with > > mandatory locking recently came up as an issue > > Is there any more interesting story there? > > > and I am wondering if there are enough people actually using and > > interested in mandatory locking that it makes sense to push people to > > support it, or if mandatory locking should be confined to it's own > > little corner of existence where it can wither and die. > > I hate mandatory locking and would be delighted, but my opinion probably > shouldn't get too much weight. > Ditto...It's really hard to believe that anyone uses them, given the well documented races in the Linux implementation. > > From what little I can glean we want to discourage people from using > > mandatory locking and to let it wither and die. A Kconfig option that > > allows mandatory locking to be disabled at compile time seems like the > > first step in making that happen. Perhaps in a decade or so when all > > linux distributions are setting the option we can remove the code. > > > > Does anyone know of any real world use cases of mandatory locking? > > Isn't byte-range locking on Windows mandatory? So Samba people might be > the ones to talk to. (Or Wine? Or anyone else doing Windows > interoperability.) > > My suspicion would be that the semantics they need are different enough > from what we support that we'd be better off ignoring it and starting > over from scratch anyway. But I could be wrong. > Windows BRLs are mandatory but they have totally different semantics. I think there is little reason to keep POSIX mandatory locks for windows emulation purposes. I'm pretty sure Samba doesn't rely on them, for instance, given that you have to use a funky mode bit combo to enable them. This patch seems like a logical step to me. I'll review it soon and will plan to queue it up for v4.5 unless there are objections between now and the next merge window. Thanks! -- Jeff Layton <jeff.layton@xxxxxxxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
