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[18.09] backport Fix mount propagation for btrfs #86
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1. There is no need to specify rw argument -- bind mounts are read-write by default. 2. There is no point in parsing /proc/self/mountinfo after performing a mount, especially if we don't check whether the fs is mounted or not -- the only outcome from it could be an error from our mountinfo parser, which makes no sense in this context. Signed-off-by: Kir Kolyshkin <[email protected]> (cherry picked from commit f01297d)
This function ensures the argument is the mount point (i.e. if it's not, it bind mounts it to itself). Signed-off-by: Kir Kolyshkin <[email protected]> (cherry picked from commit 8abadb3)
For some reason, shared mount propagation between the host
and a container does not work for btrfs, unless container
root directory (i.e. graphdriver home) is a bind mount.
The above issue was reproduced on SLES 12sp3 + btrfs using
the following script:
#!/bin/bash
set -eux -o pipefail
# DIR should not be under a subvolume
DIR=${DIR:-/lib}
MNT=$DIR/my-mnt
FILE=$MNT/file
ID=$(docker run -d --privileged -v $DIR:$DIR:rshared ubuntu sleep 24h)
docker exec $ID mkdir -p $MNT
docker exec $ID mount -t tmpfs tmpfs $MNT
docker exec $ID touch $FILE
ls -l $FILE
umount $MNT
docker rm -f $ID
which fails this way:
+ ls -l /lib/my-mnt/file
ls: cannot access '/lib/my-mnt/file': No such file or directory
meaning the mount performed inside a priviledged container is not
propagated back to the host (even if all the mounts have "shared"
propagation mode).
The remedy to the above is to make graphdriver home a bind mount.
Signed-off-by: Kir Kolyshkin <[email protected]>
(cherry picked from commit 16d822b)
kolyshkin
changed the title
seemethere
approved these changes
Oct 12, 2018
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Backport of moby#38026. Clean cherry-pick, no issues.