should CONFIG_TMPFS_POSIX_ACL be so easily deselectable?

From: Robert P. J. Day
Date: Fri Jun 17 2011 - 18:06:20 EST

long story short: in updating to a slightly newer hand-rolled
kernel (2.6.39-rc7 -> 3.0.0-rc3) on my ubuntu system, i somehow (no
idea how) managed to deselect CONFIG_TMPFS_POSIX_ACL without realizing
it. the consequences of this were that sound suddenly disappeared
under the new kernel, for a fairly obvious reason -- ALSA needs ACLs
under /dev to give R/W access to the user to the device files under

as i said, i have no idea how i managed to do this but i eventually
tracked it down, re-selected that option, rebuilt and i have sound
again. but i noticed that in fs/Kconfig, that option is independently
selectable from TMPFS, so it's (as i learned) deviously easy to
deselect, with annoying consequences.

more to the point, given the apparent necessity of ACLs under /dev
for proper sound operation, the help info for that option seems a bit

bool "Tmpfs POSIX Access Control Lists"
depends on TMPFS
... snip ...
If you don't know what Access Control Lists are, say N.

yeah, i think that help line might not want to dismiss tmpfs ACLs
quite so quickly. thoughts?


p.s. i do notice a fairly recent change to that config file related
to this:

commit 4db70f73e56961b9bcdfd0c36c62847a18b7dbb5
Author: Eric Paris <eparis@xxxxxxxxxx>
Date: Wed May 25 19:49:18 2011 -0700

tmpfs: fix XATTR N overriding POSIX_ACL Y

Choosing TMPFS_XATTR default N was switching off TMPFS_POSIX_ACL,
even if it had been Y in oldconfig; and Linus reports that PulseAudio
goes subtly wrong unless it can use ACLs on /dev/shm.

Make TMPFS_POSIX_ACL select TMPFS_XATTR (and depend upon TMPFS),
and move the TMPFS_POSIX_ACL entry before the TMPFS_XATTR entry,
to avoid asking unnecessary questions then ignoring their answers.


Robert P. J. Day Ottawa, Ontario, CANADA

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at