On Thu, 2017-05-04 at 15:34 +0200, Karel Zak wrote: > On Thu, May 04, 2017 at 02:06:51PM +0100, David Howells wrote: > > Karel Zak <kzak@xxxxxxxxxx> wrote: > > > The very basic mount(2) problem is that you have to parse > > > /proc/self/mountinfo to get information about the mounted filesystem. > > > It seems that your read() is also one way communication. > > > > > > What we really need is to have a way how to specify *what* you want to > > > read. The error message is not enough, I want to know the finally used > > > mount options, mount ID, etc. It would be nice to have something like > > > > > > > > > fsmount(mfd, AT_FDCWD, "/mnt", 0); > > > > > > write(mfd, "o"); > > > read(mfd, ....); // read mount options > > > > > > write(mdf, "i"); > > > read(mfd, ....); // read mount ID > > > > > > > > > but it seems ugly. Maybe introduce another function like > > > > > > fsinfo(mdf, "o", buf, bufsz) > > > Not sure that it's any prettier, but you could use an ioctl to switch between different read requests: ioctl(mfd, FSOPEN_READ_OPTIONS); read(mfd, ....); ioctl(mfd, FSOPEN_READ_MOUNT_ID); read(mfd, ....); > > > to get mount options (etc.) and to avoid separate write & read. > > > > What is it you're trying to do? Just read back the state of the new mount? > > ...read back the state of the new mount, because for example mount > options can be modified by FS driver. It would be also nice to have > API to get state of arbitrary mount without parsing mountinfo (the > file is huge on some systems). > -- Jeff Layton <jlayton@xxxxxxxxxx>
