TL;DR: check for IsExist(err) after a failed MkdirAll() is both
redundant and wrong -- so two reasons to remove it.
Quoting MkdirAll documentation:
> MkdirAll creates a directory named path, along with any necessary
> parents, and returns nil, or else returns an error. If path
> is already a directory, MkdirAll does nothing and returns nil.
This means two things:
1. If a directory to be created already exists, no error is
returned.
2. If the error returned is IsExist (EEXIST), it means there exists
a non-directory with the same name as MkdirAll need to use for
directory. Example: we want to MkdirAll("a/b"), but file "a"
(or "a/b") already exists, so MkdirAll fails.
The above is a theory, based on quoted documentation and my UNIX
knowledge.
3. In practice, though, current MkdirAll implementation [1] returns
ENOTDIR in most of cases described in #2, with the exception when
there is a race between MkdirAll and someone else creating the
last component of MkdirAll argument as a file. In this very case
MkdirAll() will indeed return EEXIST.
Because of #1, IsExist check after MkdirAll is not needed.
Because of #2 and #3, ignoring IsExist error is just plain wrong,
as directory we require is not created. It's cleaner to report
the error now.
Note this error is all over the tree, I guess due to copy-paste,
or trying to follow the same usage pattern as for Mkdir(),
or some not quite correct examples on the Internet.
[1] https://github.com/golang/go/blob/f9ed2f75/src/os/path.go
Signed-off-by: Kir Kolyshkin <kir@openvz.org>
Sometimes subsystem can be mounted to path like "subsystem1,subsystem2",
so we need to handle this.
Signed-off-by: Alexander Morozov <lk4d4@docker.com>
This is needed because for nested containers cgroups. Without this patch
they creating unnecessary intermediate cgroup like:
/sys/fs/cgroup/memory/system.slice/docker-9409d9f0b68fb9e9d7d532d5b3f35e7c7f9cca1312af392ae3b28436f1f2998f.scope/system.slice/docker-9409d9f0b68fb9e9d7d532d5b3f35e7c7f9cca1312af392ae3b28436f1f2998f.scope/docker/908ebcc9c13584a14322ec070bd971e0de62f126c0cd95c079acdb99990ad3a3
It is because in /proc/self/cgroup we see paths from host, and they don't
exist in container.
Signed-off-by: Alexander Morozov <lk4d4@docker.com>
Alexander Morozov
Qiang Huang
Mrunal Patel
Shijiang Wei
Kir Kolyshkin
Michael Crosby