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| author | Amir Goldstein <amir73il@gmail.com> | 2017-09-29 10:21:21 +0300 |
|---|---|---|
| committer | Miklos Szeredi <mszeredi@redhat.com> | 2017-10-05 15:53:18 +0200 |
| commit | 85fdee1eef1a9e48ad5716916677e0c5fbc781e3 (patch) | |
| tree | 9f2096f14047af5ce55aacfc9a7b90a7f7405f09 /Documentation/filesystems/overlayfs.txt | |
| parent | 5820dc0888d302ac05f8b91ffdf7e4e53b4fbf53 (diff) | |
| download | lwn-85fdee1eef1a9e48ad5716916677e0c5fbc781e3.tar.gz lwn-85fdee1eef1a9e48ad5716916677e0c5fbc781e3.zip | |
ovl: fix regression caused by exclusive upper/work dir protection
Enforcing exclusive ownership on upper/work dirs caused a docker
regression: https://github.com/moby/moby/issues/34672.
Euan spotted the regression and pointed to the offending commit.
Vivek has brought the regression to my attention and provided this
reproducer:
Terminal 1:
mount -t overlay -o workdir=work,lowerdir=lower,upperdir=upper none
merged/
Terminal 2:
unshare -m
Terminal 1:
umount merged
mount -t overlay -o workdir=work,lowerdir=lower,upperdir=upper none
merged/
mount: /root/overlay-testing/merged: none already mounted or mount point
busy
To fix the regression, I replaced the error with an alarming warning.
With index feature enabled, mount does fail, but logs a suggestion to
override exclusive dir protection by disabling index.
Note that index=off mount does take the inuse locks, so a concurrent
index=off will issue the warning and a concurrent index=on mount will fail.
Documentation was updated to reflect this change.
Fixes: 2cac0c00a6cd ("ovl: get exclusive ownership on upper/work dirs")
Cc: <stable@vger.kernel.org> # v4.13
Reported-by: Euan Kemp <euank@euank.com>
Reported-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Diffstat (limited to 'Documentation/filesystems/overlayfs.txt')
| -rw-r--r-- | Documentation/filesystems/overlayfs.txt | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/Documentation/filesystems/overlayfs.txt b/Documentation/filesystems/overlayfs.txt index 36f528a7fdd6..8caa60734647 100644 --- a/Documentation/filesystems/overlayfs.txt +++ b/Documentation/filesystems/overlayfs.txt @@ -210,8 +210,11 @@ path as another overlay mount and it may use a lower layer path that is beneath or above the path of another overlay lower layer path. Using an upper layer path and/or a workdir path that are already used by -another overlay mount is not allowed and will fail with EBUSY. Using +another overlay mount is not allowed and may fail with EBUSY. Using partially overlapping paths is not allowed but will not fail with EBUSY. +If files are accessed from two overlayfs mounts which share or overlap the +upper layer and/or workdir path the behavior of the overlay is undefined, +though it will not result in a crash or deadlock. Mounting an overlay using an upper layer path, where the upper layer path was previously used by another mounted overlay in combination with a |