From de2447c2abc7925451bd345e1a42e1b2d845471f Mon Sep 17 00:00:00 2001 From: Mike Sul Date: Wed, 13 Sep 2023 09:13:13 +0200 Subject: [PATCH] daemon: overlay2: Write layer metadata atomically When the daemon process or the host running it is abruptly terminated, the layer metadata file can become inconsistent on the file system. Specifically, `link` and `lower` files may exist but be empty, leading to overlay mounting errors during layer extraction, such as: "failed to register layer: error creating overlay mount to : too many levels of symbolic links." This commit introduces the use of `AtomicWriteFile` to ensure that the layer metadata files contain correct data when they exist on the file system. Signed-off-by: Mike --- daemon/graphdriver/overlay2/overlay.go | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/daemon/graphdriver/overlay2/overlay.go b/daemon/graphdriver/overlay2/overlay.go index 73d87d9690..9ca73c28b0 100644 --- a/daemon/graphdriver/overlay2/overlay.go +++ b/daemon/graphdriver/overlay2/overlay.go @@ -23,6 +23,7 @@ import ( "github.com/docker/docker/pkg/containerfs" "github.com/docker/docker/pkg/directory" "github.com/docker/docker/pkg/idtools" + "github.com/docker/docker/pkg/ioutils" "github.com/docker/docker/pkg/parsers" "github.com/docker/docker/quota" units "github.com/docker/go-units" @@ -383,7 +384,7 @@ func (d *Driver) create(id, parent string, opts *graphdriver.CreateOpts) (retErr } // Write link id to link file - if err := os.WriteFile(path.Join(dir, "link"), []byte(lid), 0o644); err != nil { + if err := ioutils.AtomicWriteFile(path.Join(dir, "link"), []byte(lid), 0o644); err != nil { return err } @@ -396,7 +397,7 @@ func (d *Driver) create(id, parent string, opts *graphdriver.CreateOpts) (retErr return err } - if err := os.WriteFile(path.Join(d.dir(parent), "committed"), []byte{}, 0o600); err != nil { + if err := ioutils.AtomicWriteFile(path.Join(d.dir(parent), "committed"), []byte{}, 0o600); err != nil { return err } @@ -405,7 +406,7 @@ func (d *Driver) create(id, parent string, opts *graphdriver.CreateOpts) (retErr return err } if lower != "" { - if err := os.WriteFile(path.Join(dir, lowerFile), []byte(lower), 0o666); err != nil { + if err := ioutils.AtomicWriteFile(path.Join(dir, lowerFile), []byte(lower), 0o666); err != nil { return err } }