32582 mount subdirs #1
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y2kpr
pushed a commit
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Dec 7, 2017
This subtle bug keeps lurking in because error checking for `Mkdir()`
and `MkdirAll()` is slightly different wrt to `EEXIST`/`IsExist`:
- for `Mkdir()`, `IsExist` error should (usually) be ignored
(unless you want to make sure directory was not there before)
as it means "the destination directory was already there"
- for `MkdirAll()`, `IsExist` error should NEVER be ignored.
Mostly, this commit just removes ignoring the IsExist error, as it
should not be ignored.
Also, there are a couple of cases then IsExist is handled as
"directory already exist" which is wrong. As a result, some code
that never worked as intended is now removed.
NOTE that `idtools.MkdirAndChown()` behaves like `os.MkdirAll()`
rather than `os.Mkdir()` -- so its description is amended accordingly,
and its usage is handled as such (i.e. IsExist error is not ignored).
For more details, a quote from my runc commit 6f82d4b (July 2015):
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 moby#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 <kolyshkin@gmail.com>
Signed-off-by: Arjun Nagineni <arjun.nagineni@utexas.edu>
Signed-off-by: Arjun Nagineni <arjun.nagineni@utexas.edu>
cpuguy83
reviewed
Jan 22, 2018
| @@ -174,18 +174,23 @@ func (m *MountPoint) Setup(mountLabel string, rootIDs idtools.IDPair, checkFun f | |||
| }() | |||
|
|
|||
| if m.Volume != nil { | |||
| // This creates new dirs when a supath is mentioned along with the volume. | |||
| if err := idtools.MkdirAllAndChownNew(m.Source, 0755, rootIDs); err != nil { | |||
There was a problem hiding this comment.
This mkdir would need to happen after mount.
| id := m.ID | ||
| if id == "" { | ||
| id = stringid.GenerateNonCryptoID() | ||
| } | ||
| path, err := m.Volume.Mount(id) | ||
| _, err := m.Volume.Mount(id) |
There was a problem hiding this comment.
This needs to use the path returned from Mount as this is provided by the volume driver.
There is no guarantee that mp.Source is populated here.
| @@ -205,7 +205,11 @@ func (daemon *Daemon) registerMountPoints(container *container.Container, hostCo | |||
| if cv, ok := v.(interface { | |||
| CachedPath() string | |||
| }); ok { | |||
| mp.Source = cv.CachedPath() | |||
| if cfg.VolumeOptions != nil && cfg.VolumeOptions.Subpath != "" { | |||
There was a problem hiding this comment.
mp.Source = cv.CachedPath()
if mp.Source != "" && cfg.VolumeOptions != nil && cfg.VolumeOptions.Subpath != "" {
mp.Source = filepath.Join(mp.Source, cfg.VolumeOptions.Subpath)
}
lordisp
reviewed
Dec 17, 2018
| @@ -205,7 +205,11 @@ func (daemon *Daemon) registerMountPoints(container *container.Container, hostCo | |||
| if cv, ok := v.(interface { | |||
| CachedPath() string | |||
| }); ok { | |||
| mp.Source = cv.CachedPath() | |||
| if cfg.VolumeOptions != nil && cfg.VolumeOptions.Subpath != "" { | |||
There was a problem hiding this comment.
I'm extreemly interested in this (actually mounting named volumes with sub-directories) but I have no clue how to use the moby project. Can someone sot some light into this?
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