image/cache: fix isValidParent logic

runcom · runcom · commit 1cf4b2b8bd92 · 2017-02-21T19:32:04.000+01:00
Signed-off-by: Antonio Murdaca &lt;runcom@redhat.com&gt;
diff --git a/image/cache/cache.go b/image/cache/cache.go
@@ -187,7 +187,7 @@ func isValidParent(img, parent *image.Image) bool {
 	if len(parent.History) >= len(img.History) {
 		return false
 	}
-	if len(parent.RootFS.DiffIDs) >= len(img.RootFS.DiffIDs) {
+	if len(parent.RootFS.DiffIDs) > len(img.RootFS.DiffIDs) {
 		return false
 	}
 
diff --git a/integration-cli/docker_cli_build_test.go b/integration-cli/docker_cli_build_test.go
@@ -5421,6 +5421,27 @@ func (s *DockerSuite) TestBuildWithFailure(c *check.C) {
 	c.Assert(result.Stdout(), checker.Not(checker.Contains), "Step 2/2 : RUN nobody")
 }
 
+func (s *DockerSuite) TestBuildCacheFromEqualDiffIDsLength(c *check.C) {
+	dockerfile := `
+		FROM busybox
+		RUN echo "test"
+		ENTRYPOINT ["sh"]`
+	ctx := fakeContext(c, dockerfile, map[string]string{
+		"Dockerfile": dockerfile,
+	})
+	defer ctx.Close()
+
+	buildImageSuccessfully(c, "build1", withExternalBuildContext(ctx))
+	id1 := getIDByName(c, "build1")
+
+	// rebuild with cache-from
+	result := buildImage("build2", withBuildFlags("--cache-from=build1"), withExternalBuildContext(ctx))
+	result.Assert(c, icmd.Success)
+	id2 := getIDByName(c, "build2")
+	c.Assert(id1, checker.Equals, id2)
+	c.Assert(strings.Count(result.Combined(), "Using cache"), checker.Equals, 2)
+}
+
 func (s *DockerSuite) TestBuildCacheFrom(c *check.C) {
 	testRequires(c, DaemonIsLinux) // All tests that do save are skipped in windows
 	dockerfile := `

Original file line number	Diff line number	Diff line change
`@@ -187,7 +187,7 @@ func isValidParent(img, parent *image.Image) bool {`
`187`	`187`	`if len(parent.History) >= len(img.History) {`
`188`	`188`	`return false`
`189`	`189`	`}`
`190`		`- if len(parent.RootFS.DiffIDs) >= len(img.RootFS.DiffIDs) {`
	`190`	`+ if len(parent.RootFS.DiffIDs) > len(img.RootFS.DiffIDs) {`
`191`	`191`	`return false`
`192`	`192`	`}`
`193`	`193`