diff --git a/daemon/graphdriver/overlay2/check.go b/daemon/graphdriver/overlay2/check.go index 851c4099c7..f29630bd2f 100644 --- a/daemon/graphdriver/overlay2/check.go +++ b/daemon/graphdriver/overlay2/check.go @@ -8,6 +8,7 @@ import ( "os" "path" "path/filepath" + "syscall" "github.com/docker/docker/pkg/system" "github.com/pkg/errors" @@ -15,10 +16,11 @@ import ( "golang.org/x/sys/unix" ) -// hasOpaqueCopyUpBug checks whether the filesystem has a bug +// doesSupportNativeDiff checks whether the filesystem has a bug // which copies up the opaque flag when copying up an opaque -// directory. When this bug exists naive diff should be used. -func hasOpaqueCopyUpBug(d string) error { +// directory or the kernel enable CONFIG_OVERLAY_FS_REDIRECT_DIR. +// When these exist naive diff should be used. +func doesSupportNativeDiff(d string) error { td, err := ioutil.TempDir(d, "opaque-bug-check") if err != nil { return err @@ -29,10 +31,13 @@ func hasOpaqueCopyUpBug(d string) error { } }() - // Make directories l1/d, l2/d, l3, work, merged + // Make directories l1/d, l1/d1, l2/d, l3, work, merged if err := os.MkdirAll(filepath.Join(td, "l1", "d"), 0755); err != nil { return err } + if err := os.MkdirAll(filepath.Join(td, "l1", "d1"), 0755); err != nil { + return err + } if err := os.MkdirAll(filepath.Join(td, "l2", "d"), 0755); err != nil { return err } @@ -75,5 +80,23 @@ func hasOpaqueCopyUpBug(d string) error { return errors.New("opaque flag erroneously copied up, consider update to kernel 4.8 or later to fix") } + // rename "d1" to "d2" + if err := os.Rename(filepath.Join(td, "merged", "d1"), filepath.Join(td, "merged", "d2")); err != nil { + // if rename failed with syscall.EXDEV, the kernel doesn't have CONFIG_OVERLAY_FS_REDIRECT_DIR enabled + if err.(*os.LinkError).Err == syscall.EXDEV { + return nil + } + return errors.Wrap(err, "failed to rename dir in merged directory") + } + // get the xattr of "d2" + xattrRedirect, err := system.Lgetxattr(filepath.Join(td, "l3", "d2"), "trusted.overlay.redirect") + if err != nil { + return errors.Wrap(err, "failed to read redirect flag on upper layer") + } + + if string(xattrRedirect) == "d1" { + return errors.New("kernel has CONFIG_OVERLAY_FS_REDIRECT_DIR enabled") + } + return nil } diff --git a/daemon/graphdriver/overlay2/overlay.go b/daemon/graphdriver/overlay2/overlay.go index f350ca9c0b..0f252e6ff2 100644 --- a/daemon/graphdriver/overlay2/overlay.go +++ b/daemon/graphdriver/overlay2/overlay.go @@ -267,8 +267,8 @@ func supportsOverlay() error { func useNaiveDiff(home string) bool { useNaiveDiffLock.Do(func() { - if err := hasOpaqueCopyUpBug(home); err != nil { - logrus.Warnf("Not using native diff for overlay2: %v", err) + if err := doesSupportNativeDiff(home); err != nil { + logrus.Warnf("Not using native diff for overlay2, this may cause degraded performance for building images: %v", err) useNaiveDiffOnly = true } })