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idtools don't chown if not needed 

In some cases (e.g. NFS), a chown may technically be a no-op but still
return `EPERM`, so only call `chown` when neccessary.

This is particularly problematic for docker users bind-mounting an NFS
share into a container.

Signed-off-by: Brian Goff <cpuguy83@gmail.com>
This commit is contained in:
Brian Goff 2017-10-02 09:47:09 -04:00
parent 1e94a4862e
commit fa9709a3fc
1 changed files with 30 additions and 8 deletions
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38
pkg/idtools/idtools_unix.go
View File

@ -26,14 +26,19 @@ func mkdirAs(path string, mode os.FileMode, ownerUID, ownerGID int, mkAll, chown
// so that we can chown all of them properly at the end. If chownExisting is false, we won't
// chown the full directory path if it exists
var paths []string
if _, err := os.Stat(path); err != nil && os.IsNotExist(err) {
paths = []string{path}
} else if err == nil && chownExisting {
stat, err := system.Stat(path)
if err == nil {
if !chownExisting {
return nil
}
// short-circuit--we were called with an existing directory and chown was requested
return os.Chown(path, ownerUID, ownerGID)
} else if err == nil {
// nothing to do; directory path fully exists already and chown was NOT requested
return nil
return lazyChown(path, ownerUID, ownerGID, stat)
}
if os.IsNotExist(err) {
paths = []string{path}
}
if mkAll {
@ -60,7 +65,7 @@ func mkdirAs(path string, mode os.FileMode, ownerUID, ownerGID int, mkAll, chown
// even if it existed, we will chown the requested path + any subpaths that
// didn't exist when we called MkdirAll
for _, pathComponent := range paths {
if err := os.Chown(pathComponent, ownerUID, ownerGID); err != nil {
if err := lazyChown(pathComponent, ownerUID, ownerGID, nil); err != nil {
return err
}
}
@ -202,3 +207,20 @@ func callGetent(args string) (io.Reader, error) {
}
return bytes.NewReader(out), nil
}
// lazyChown performs a chown only if the uid/gid don't match what's requested
// Normally a Chown is a no-op if uid/gid match, but in some cases this can still cause an error, e.g. if the
// dir is on an NFS share, so don't call chown unless we absolutely must.
func lazyChown(p string, uid, gid int, stat *system.StatT) error {
if stat == nil {
var err error
stat, err = system.Stat(p)
if err != nil {
return err
}
}
if stat.UID() == uint32(uid) && stat.GID() == uint32(gid) {
return nil
}
return os.Chown(p, uid, gid)
}