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SubjectRe: Upcoming: Notifications, FS notifications and fsinfo()
On Mon, Mar 30, 2020 at 10:28:56PM +0200, Miklos Szeredi wrote:
> All this could be solved with a string key/value representation of the
> same data, with minimal performance loss on encoding/parsing. The
> proposed fs interface[1] is one example of that, but I could also
> imagine a syscall based one too.

Yes, key/value is possible solution. The question is if we really
need to add extra /sys-like filesystem to get key/value ;-) I can
imagine key/value from FD based interface without open/read/close for
each attribute,

fd = open("/mnt", O_PATH);
fsinfo(fd, "propagation", buf, sizeof(buf));
fsinfo(fd, "fstype", buf, sizeof(buf));
close(fd);

why I need /mountfs/<id>/propagation and /mountfs/<id>/fstype to get
the same? It sounds like over-engineering without any extra bonus.

Anyway, if we have FD based interfaces like fsopen(), fsmount(),
open_tree() and move_mount() then it sounds strange that you cannot
use the FD to ask kernel for the mount node attributes and you need
to open and read another /sys-like files.

IMHO it would be nice that after open(/mnt, O_PATH) I can do whatever
with the mount point (umount, move, reconfigure, query, etc.). Please,
try to keep it simple and consistent ;-)

Karel

--
Karel Zak <kzak@redhat.com>
http://karelzak.blogspot.com

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