storage e2e test: remove race when setting up loopback device

CI has shown occasional failures stemming from an -EBUSY when test/e2e/storage/persistent_volumes-local.go aka "PersistentVolumes-local" attempts to do losetup. Looking at the code, it has a clear race between querying the current free loopback device and later explicitly attempting to loopback setup a file at the queried device node. Losetup nowadays includes the logic to handle this for the user, if the '-f' option is used instead of naming the desired target loopback device explicitly. It is safe to presume a suitable losetup is present as the '-f' option is used elsewhere in the test, and it is safe to not record the allocated device, as it is already queried on the fly elsewhere in the test ahead of other commands which need to know an already created loopback device's node name. This patch should result in less flakes for this test case. Signed-off-by: Tim Pepper <tpepper@vmware.com>

storage e2e test: remove race when setting up loopback device
91b0ecc0 · Tim Pepper · 819253dd · 91b0ecc0
Commit 91b0ecc0 authored Aug 09, 2018 by Tim Pepper
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persistent_volumes-local.go test/e2e/storage/persistent_volumes-local.go +2 -3

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--- a/test/e2e/storage/persistent_volumes-local.go
+++ b/test/e2e/storage/persistent_volumes-local.go
@@ -1324,9 +1324,8 @@ func createAndMapBlockLocalVolume(config *localTestConfig, dir string, node *v1.
 	mkdirCmd := fmt.Sprintf("mkdir -p %s", dir)
 	// Create 10MB file that will serve as the backing for block device.
 	ddCmd := fmt.Sprintf("dd if=/dev/zero of=%s/file bs=512 count=20480", dir)
-	losetupLoopDevCmd := fmt.Sprintf("E2E_LOOP_DEV=$(sudo losetup -f) && echo ${E2E_LOOP_DEV}")
+	losetupCmd := fmt.Sprintf("sudo losetup -f  %s/file", dir)
-	losetupCmd := fmt.Sprintf("sudo losetup ${E2E_LOOP_DEV} %s/file", dir)
+	err := issueNodeCommand(config, fmt.Sprintf("%s && %s && %s", mkdirCmd, ddCmd, losetupCmd), node)
-	err := issueNodeCommand(config, fmt.Sprintf("%s && %s && %s && %s", mkdirCmd, ddCmd, losetupLoopDevCmd, losetupCmd), node)
 	Expect(err).NotTo(HaveOccurred())
 }