time delay before changes become visible

[Michael Towers]

We are getting a strange 'lag' behaviour using aufs (well it seems
strange to us). It's happening in a live CD environment using squashfs.

After certain file-system operations - apparently where a large number
of files get added or updated, but exactly when it happens and when not
is not clear - it takes a long time, sometimes more than a minute,
before the updates are visible in the aufs mount (although they are
immediately visible in the write branch).

Here is a report of how it manifests itself - it is unfortunately very
specific to
Archlinux so it might not help you much ...

<<<It seems like there is still something wrong with aufs lag time.
Here's the problem:

- I made a live cd using your latest larch scripts.
- I booted into the live cd and did a "pacman -Sl" and pacman lists all
packages in the repos, about 3925 packages.
- I did a "pacman -Syu" and all my packages were up to date. Immediately
after that I do a "pacman -Sl" again and nothing is listed anymore.
- I wait about 1 minute and do a "pacman -Sl" and the 3925 packages are
listed again.>>>

As you can see below, in essence each root directory has its own aufs
mount with a base branch and an overlay branch (both in squashfs) plus a
write branch in tmpfs. In the example where the problem arose, the many
files and directories were in /var/lib/pacman subdirectories.

----------------

aufs version 20070611 (but also other versions, I think an earlier one
was worse)
kernel 2.6.21.5

----------------

Here is how the aufs module was built (Archlinux PKGBUILD, I hope it's
clear enough):

pkgname=aufs
_kerndir=2.6.21-ARCH
pkgver=2.6.21cvs
pkgrel=2
pkgdesc="A unification file system ('another unionfs')"
arch=(i686)
url="http://aufs.sourceforge.net";
depends=('kernel26>=2.6.21' 'kernel26<=2.6.22')
_cvsroot=":pserver:anonymous:@aufs.cvs.sourceforge.net:/cvsroot/aufs"
_cvsmod="aufs"

build() {
  msg "Connecting to $_cvsmod.sourceforge.net CVS server...."
  cvs -d$_cvsroot checkout $_cvsmod

  msg "CVS checkout done or server timeout"
  msg "Starting make..."

  cp -r $_cvsmod $_cvsmod-build
  cd $_cvsmod-build
  make KDIR=/lib/modules/${_kerndir}/build -f local.mk || return 1
  #mkdir -p ${startdir}/pkg/sbin
  #install -m 500 -p mount.aufs umount.aufs auplink aulchown
${startdir}/pkg/sbin
  install -D -m 644 -p aufs.ko
${startdir}/pkg/lib/modules/${_kerndir}/kernel/fs/aufs/aufs.ko
}

----------------

/proc/mounts:

rootfs / rootfs rw 0 0
tmpfs / tmpfs rw 0 0
/dev/sr0 /.livesys/livecd iso9660 ro 0 0
/dev/loop0 /.livesys/base squashfs ro 0 0
/dev/loop1 /.livesys/etc squashfs ro 0 0
/dev/loop0 /bin squashfs ro 0 0
/dev/loop0 /lib squashfs ro 0 0
/dev/loop0 /sbin squashfs ro 0 0
/dev/loop0 /usr squashfs ro 0 0
/dev/loop1 /etc squashfs ro 0 0
none /proc proc rw 0 0
/dev/loop2 /.livesys/system squashfs ro 0 0
/dev/loop3 /.livesys/overlay squashfs ro 0 0
aufs /bin aufs

0 0
aufs /boot aufs

0 0
aufs /etc aufs

0 0
aufs /home aufs

0 0
aufs /lib aufs

0 0
aufs /opt aufs

0 0
aufs /root aufs

0 0
aufs /sbin aufs

0 0
aufs /srv aufs

0 0
aufs /usr aufs

0 0
aufs /var aufs

0 0
aufs /larch aufs

0 0
none /sys sysfs rw 0 0
none /dev ramfs rw 0 0
none /proc/bus/usb usbfs rw 0 0
none /dev/pts devpts rw 0 0
none /dev/shm tmpfs rw 0 0

----------------

/sys/fs/aufs/* attached as aufs.tar.gz

----------------

Best wishes,
mt

rw,xino=/.livesys/.bin_w/.aufs.xino,br:/.livesys/.bin_w=rw:/.livesys/base/bin=ro:/.livesys/system/bin=ro rw,xino=/.livesys/.boot_w/.aufs.xino,br:/.livesys/.boot_w=rw:/.livesys/system/boot=ro rw,xino=/.livesys/.etc_w/.aufs.xino,br:/.livesys/.etc_w=rw:/.livesys/etc/etc=ro:/.livesys/system/etc=ro rw,xino=/.livesys/.home_w/.aufs.xino,br:/.livesys/.home_w=rw:/.livesys/system/home=ro rw,xino=/.livesys/.lib_w/.aufs.xino,br:/.livesys/.lib_w=rw:/.livesys/base/lib=ro:/.livesys/system/lib=ro rw,xino=/.livesys/.opt_w/.aufs.xino,br:/.livesys/.opt_w=rw:/.livesys/system/opt=ro rw,xino=/.livesys/.root_w/.aufs.xino,br:/.livesys/.root_w=rw:/.livesys/overlay/root=ro+wh:/.livesys/system/root=ro rw,xino=/.livesys/.sbin_w/.aufs.xino,br:/.livesys/.sbin_w=rw:/.livesys/base/sbin=ro:/.livesys/system/sbin=ro rw,xino=/.livesys/.srv_w/.aufs.xino,br:/.livesys/.srv_w=rw:/.livesys/system/srv=ro rw,xino=/.livesys/.usr_w/.aufs.xino,br:/.livesys/.usr_w=rw:/.livesys/base/usr=ro:/.livesys/system/usr=ro rw,xino=/.livesys/.var_w/.aufs.xino,br:/.livesys/.var_w=rw:/.livesys/system/var=ro rw,xino=/.livesys/.larch_w/.aufs.xino,br:/.livesys/.larch_w=rw:/.livesys/overlay/larch=ro

aufs.tar.gz
Description: GNU Zip compressed data

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