On Sun, Sep 23, 2018 at 11:45:17PM +0100, David Howells wrote:
> Christian Brauner <christian@xxxxxxxxxx> wrote:
>
> > Of course, I'm not sure what the reasons for all of the other arguments to
> > this function are since it's not yet implemented.
>
> Well, dfd, path and atflags are pretty standard. atflags conveys things like
> AT_EMPTY_PATH or AT_SYMLINK_NOFOLLOW and dfd conveys a file descriptor
> pointing to a vfs object or AT_FDCWD.
>
> > Seems that attr_values and attr_mask could be compacted to a single
> > attr_mask maybe?
>
> If you don't have a mask, you can't really do recursion. Without the mask,
> you have to supply the entire set of options absolutely - and this would get
> stamped on everything in the target range.
>
> With a mask in combination with the set of desired values, you can turn on or
> off a specific subset of the attributes without affecting the rest - without
> needing to know the rest.
Ok, understood. What about passing the different attrs as a struct?
struct mount_attr {
unsigned int attr_cmd,
unsigned int attr_values,
unsigned int attr_mask,
};
mount_setattr(int dfd, const char *path, unsigned int atflags,
struct mount_attr *attr);
I find that to be a little cleaner in all honesty.
One could also add a version argument similar to what we currently do
for vfs fcaps so that kernel and userspace can easily navigate
compabitility when a new member gets added or removed in later releases.
Christian
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