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// -*- Mode: Go; indent-tabs-mode: t -*-
/*
* Copyright (C) 2019 Canonical Ltd
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 3 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
package gadget
import (
"fmt"
"path/filepath"
"github.com/snapcore/snapd/dirs"
"github.com/snapcore/snapd/logger"
"github.com/snapcore/snapd/osutil"
"github.com/snapcore/snapd/osutil/disks"
)
var evalSymlinks = filepath.EvalSymlinks
// FindDeviceForStructure attempts to find an existing block device matching
// given volume structure, by inspecting its name and, optionally, the
// filesystem label. Assumes that the host's udev has set up device symlinks
// correctly.
func FindDeviceForStructure(vs *VolumeStructure) (string, error) {
var candidates []string
if vs.Name != "" {
byPartlabel := filepath.Join(dirs.GlobalRootDir, "/dev/disk/by-partlabel/", disks.BlkIDEncodeLabel(vs.Name))
candidates = append(candidates, byPartlabel)
}
if vs.HasFilesystem() {
fsLabel := vs.Label
if fsLabel == "" && vs.Name != "" {
// when image is built and the structure has no
// filesystem label, the structure name will be used by
// default as the label
fsLabel = vs.Name
}
if fsLabel != "" {
candLabel, err := disks.CandidateByLabelPath(fsLabel)
if err == nil {
candidates = append(candidates, candLabel)
} else {
logger.Debugf("no by-label candidate for %q: %v", fsLabel, err)
}
}
}
var found string
var match string
for _, candidate := range candidates {
if !osutil.FileExists(candidate) {
continue
}
if !osutil.IsSymlink(candidate) {
// /dev/disk/by-label/* and /dev/disk/by-partlabel/* are
// expected to be symlink
return "", fmt.Errorf("candidate %v is not a symlink", candidate)
}
target, err := evalSymlinks(candidate)
if err != nil {
return "", fmt.Errorf("cannot read device link: %v", err)
}
if found != "" && target != found {
// partition and filesystem label links point to
// different devices
return "", fmt.Errorf("conflicting device match, %q points to %q, previous match %q points to %q",
candidate, target, match, found)
}
found = target
match = candidate
}
if found == "" {
return "", ErrDeviceNotFound
}
return found, nil
}
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