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daemon: overlay2: Write layer metadata atomically

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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 <path>:
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 <mike.sul@foundries.io>
This commit is contained in:
Mike Sul 2023-09-13 09:13:13 +02:00 committed by Mike
parent 76915b16e7
commit de2447c2ab
No known key found for this signature in database
GPG key ID: 4259A66D08BC3BCA
1 changed files with 4 additions and 3 deletions
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7
daemon/graphdriver/overlay2/overlay.go
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@ -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
}
}