On Fri, Aug 20, 2021 at 9:36 AM Amir Goldstein <amir73il@xxxxxxxxx> wrote: > > On Thu, Aug 19, 2021 at 11:32 PM Linus Torvalds > <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > > > > On Thu, Aug 19, 2021 at 1:18 PM Jeff Layton <jlayton@xxxxxxxxxx> wrote: > > > > > > Now that I think about it a little more, I actually did get one > > > complaint a few years ago: > > > > > > Someone had upgraded from an earlier distro that supported the -o mand > > > mount option to a later one that had disabled it, and they had an (old) > > > fstab entry that specified it. > > > > Hmm. We might be able to turn the "return -EINVAL" into just a warning. > > > > Yes, yes, currently if you turn off CONFIG_MANDATORY_FILE_LOCKING, we > > already do that > > > > VFS: "mand" mount option not supported > > > > warning print, but then we fail the mount. > > > > If CONFIG_MANDATORY_FILE_LOCKING goes away entirely, it might make > > sense to turn that warning into something bigger, but then let the > > mount continue - since now that "mand" flag would be purely a legacy > > thing. > > > > And yes, if we do that, we'd want the warning to be a big ugly thing, > > just to make people very aware of it happening. Right now it's a > > one-liner that is easy to miss, and the "oh, the mount failed" is the > > thing that hopefully informs people about the fact that they need to > > enable CONFIG_MANDATORY_FILE_LOCKING. > > > > The logic being that if you can no longer enable mandatory locking in > > the kernel, the current hard failure seems overly aggressive (and > > might cause boot failures and inability to fix/report things when it > > possibly keeps you from using the system at all). > > > > Allow me to play the devil's advocate here - if fstab has '-o mand' we have > no way of knowing if any application is relying on '-o mand' and adding > more !!!!! to the warning is mostly good for clearing our conscious ;-) > > Not saying we cannot resort to that and not saying there is an easy > solution, but there is one more solution to consider - force rdonly mount. > Yes, it could break some systems and possibly fail boot, but then again > an ext4 fs can already become rdonly due to errors, so it wouldn't > be the first time that sysadmins/users run into this behavior. > Adding an anecdote - this week I got a report from field support engineers about failure to assemble a RAID0 array, which led to this warning that *requires* user intervention, in the worse case for boot device it requires changing kernel boot params: md/raid0:%s: cannot assemble multi-zone RAID0 with default_layout setting md/raid0: please set raid.default_layout to 1 or 2 c84a1372df92 md/raid0: avoid RAID0 data corruption due to layout confusion. There is no way I would have gotten this report from the field if a failure was not involved... The rdonly mount is only needed to get the attention of support people to look the the kernel logs and find the warning - at this point, not too many !!!!! are needed ;-) So we could make 'mand' an alias to 'ro' and print a warning that says: "'mand' mount option is deprecated, please fix your init scripts. For caution, your filesystem was mounted rdonly, feel free to remount rw and move on..." Thanks, Amir.
