[RFC][PATCH 00/12] Enhanced file stat system call

[J. Bruce Fields]

On Fri, Nov 20, 2015 at 04:28:35PM +0000, David Howells wrote:
> Martin Steigerwald <martin at lichtvoll.de> wrote:
> 
> > Any plans to add limitations of filesystem to the call like maximum file
> > size?  I know its mostly relevant for just for FAT32, but on any account
> > rather than trying to write 4 GiB and then file, it would be good to at some
> > time get a dialog at the beginning of the copy.
> 
> Adding filesystem limits can be done.  I got a shopping list of things people
> wanted a while back and I've worked off of that list.  I can add other things
> - that's on of the reasons I left room for expansion.

I ran across systemd/src/basic/path-util.c:fd_is_mount_point() the other
day, and the contortions it goes through made me wonder if we should
also add mnt_id and/or an is_mountpoint boolean--it's annoying to have
to do name_to_handle_at() (not supported on all filesystems) just to get
mnt_id.

(Looking at it now I see it falls back on reading mount id from
/proc/self/fdinfo/<fd>.  Maybe that's good enough.  May depend on
whether there's a potential user that doesn't want to assume access to
/proc?)

--b.