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SubjectRe: [RFC PATCH 2/3] add statmnt(2) syscall
On Wed, Sep 13, 2023 at 9:25 AM Miklos Szeredi <mszeredi@redhat.com> wrote:
>
> Add a way to query attributes of a single mount instead of having to parse
> the complete /proc/$PID/mountinfo, which might be huge.
>
> Lookup the mount by the old (32bit) or new (64bit) mount ID. If a mount
> needs to be queried based on path, then statx(2) can be used to first query
> the mount ID belonging to the path.
>
> Design is based on a suggestion by Linus:
>
> "So I'd suggest something that is very much like "statfsat()", which gets
> a buffer and a length, and returns an extended "struct statfs" *AND*
> just a string description at the end."
>
> The interface closely mimics that of statx.
>
> Handle ASCII attributes by appending after the end of the structure (as per
> above suggestion). Allow querying multiple string attributes with
> individual offset/length for each. String are nul terminated (termination
> isn't counted in length).
>
> Mount options are also delimited with nul characters. Unlike proc, special
> characters are not quoted.
>

Thank you for writing this patch. I wish that this had existed the many times
I've written parsers for mounts files in my life.

What do you think about exposing the locked flags, a la what happens
on propagation of mount across user namespaces?

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