[systemd-devel] Topics for the Linux Storage, Filesystem & MM Summit

Lennart Poettering lennart at poettering.net
Thu Feb 27 15:09:00 PST 2014

On Thu, 27.02.14 14:44, David Timothy Strauss (david at davidstrauss.net) wrote:

> I'll be attending the Linux Storage, Filesystem & MM Summit in March.
> Are there any topics germane to systemd I should put on the agenda or
> discuss with other folks there?
> Things I have in mind so far:
>  * Next steps for mount and automount units
>  * That's it so far.
> I'm mostly attending for my company's FuseDAV/Valhalla work, but I'd
> like to effectively represent systemd as well.

Hmm, there are a couple of things on my wishlist:

- quota for tmpfs

- saner autofs elapse logic (no blocking ioctls...)

- uuids for btrfs subvols

- a umount (or maybe last-change) timestamp in the btrfs superblock,
  which we can use to initialize the system clock from if a machine
  lacks RTC or has a dead battery. Even better: a unified ioctl() to
  query this from all file systems the same way.

- fanotify: accessible to unprivileged users

- fanotify: events for renames

- fanotify: pass info about open() flags to monitoring processes

- fanotify: when getting getting a notification for close, actually
  get information whether the file was changed or not

- an ioctl-based way to change FAT file system labels

- cheaper xattrs. currently querying xattrs on most file systems is
  prohibitively slow, since it results in seeks and whatnot. Which has
  the result that pretty nobody uses them. One way to make things better
  would be to maybe expose in some fstat2() call a flag whether there
  even are xattrs, so that apps could check for that flag before
  actually trying to read them

- An API to query the birthtime of files. ext234 actually stores that
  and keeps it up-to-date, but there's no API to get to this data

- An fsetxattrat() call, so that race-free selinux relabelling can be

- a way to mark an entire tree of mounts read-only with one call. i.e. a
  working combination of MS_REC|MS_RDONLY

- Allow creating read-only bind mounts in a single mount() invocation,
  instead of requiring two. Similar, a way to set the propagation
  settings for a mount when one creates it, rather than requiring two
  mount() invocations for that.

- Swappiness control for individual pages via madvise()

- volatile ranges

- A better SIGBUS/SIGSEGV API (for accessing invalidated memory maps),
  that actually works for libraries. i.e. a sane way how libraries can
  register handlers for specific memory regions they maage. Currently
  there can only be one handler for the entire process which makes this
  totally unavailable for libraries, since they'd always step on each
  others toes. Probably hard one to get into the brains of kernel guys,
  since for them that is a userspace problem.

Oh, and note that Al Viro dislikes systemd and particularly me with a
passion. It's probably not good mentioning us in any discussion with


Lennart Poettering, Red Hat

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