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Support for hardlinks to symlinks

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This is a specialized use-case, but it is indeed possible to do this
and can be used if xattrs are attached to the symlink.
This commit is contained in:
John K. Luebs
2023-10-03 23:46:00 -05:00
parent 52e628ac93
commit 4934df4e08
5 changed files with 165 additions and 40 deletions
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76
src/duplicacy_entry.go
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@@ -8,6 +8,7 @@ import (
"crypto/sha256"
"encoding/base64"
"encoding/json"
"errors"
"fmt"
"io/ioutil"
"os"
@@ -23,6 +24,11 @@ import (
"github.com/vmihailenco/msgpack"
)
const (
entrySymHardLinkRootChunkMarker = -72
entrySymHardLinkTargetChunkMarker = -73
)
// This is the hidden directory in the repository for storing various files.
var DUPLICACY_DIRECTORY = ".duplicacy"
var DUPLICACY_FILE = ".duplicacy"
@@ -518,11 +524,23 @@ func (entry *Entry) IsComplete() bool {
}
func (entry *Entry) IsHardlinkedFrom() bool {
return entry.IsFile() && len(entry.Link) > 0 && entry.Link != "/"
return (entry.IsFile() && len(entry.Link) > 0 && entry.Link != "/") || (entry.IsLink() && entry.StartChunk == entrySymHardLinkTargetChunkMarker)
}
func (entry *Entry) IsHardlinkRoot() bool {
return entry.IsFile() && entry.Link == "/"
return (entry.IsFile() && entry.Link == "/") || (entry.IsLink() && entry.StartChunk == entrySymHardLinkRootChunkMarker)
}
func (entry *Entry) GetHardlinkId() (int, error) {
if entry.IsLink() {
if entry.StartChunk != entrySymHardLinkTargetChunkMarker {
return 0, errors.New("Symlink entry not marked as hardlinked")
}
return entry.StartOffset, nil
} else {
i, err := strconv.ParseUint(entry.Link, 16, 64)
return int(i), err
}
}
func (entry *Entry) GetPermissions() os.FileMode {
@@ -789,6 +807,42 @@ func ListEntries(top string, path string, patterns []string, nobackupFile string
if len(patterns) > 0 && !MatchPath(entry.Path, patterns) {
continue
}
if f.Mode()&(os.ModeNamedPipe|os.ModeSocket|os.ModeDevice) != 0 {
LOG_WARN("LIST_SKIP", "Skipped non-regular file %s", entry.Path)
skippedFiles = append(skippedFiles, entry.Path)
continue
}
var linkKey *listEntryLinkKey
if runtime.GOOS != "windows" && !entry.IsDir() {
if stat := f.Sys().(*syscall.Stat_t); stat != nil && stat.Nlink > 1 {
k := listEntryLinkKey{dev: uint64(stat.Dev), ino: uint64(stat.Ino)}
if linkIndex, seen := listingState.linkTable[k]; seen {
if linkIndex == -1 {
LOG_DEBUG("LIST_EXCLUDE", "%s is excluded by attribute (hardlink)", entry.Path)
continue
}
entry.Size = 0
if entry.IsLink() {
entry.StartChunk = entrySymHardLinkTargetChunkMarker
entry.StartOffset = linkIndex
} else {
entry.Link = strconv.FormatInt(int64(linkIndex), 16)
}
} else {
if entry.IsLink() {
entry.StartChunk = entrySymHardLinkRootChunkMarker
} else {
entry.Link = "/"
}
listingState.linkTable[k] = -1
linkKey = &k
}
}
}
if entry.IsLink() {
isRegular := false
isRegular, entry.Link, err = Readlink(joinPath(top, entry.Path))
@@ -830,24 +884,6 @@ func ListEntries(top string, path string, patterns []string, nobackupFile string
}
}
var linkKey *listEntryLinkKey
if stat, ok := f.Sys().(*syscall.Stat_t); entry.IsFile() && ok && stat != nil && stat.Nlink > 1 {
k := listEntryLinkKey{dev: uint64(stat.Dev), ino: uint64(stat.Ino)}
if linkIndex, seen := listingState.linkTable[k]; seen {
if linkIndex == -1 {
LOG_DEBUG("LIST_EXCLUDE", "%s is excluded by attribute (hardlink)", entry.Path)
continue
}
entry.Size = 0
entry.Link = strconv.FormatInt(int64(linkIndex), 16)
} else {
entry.Link = "/"
listingState.linkTable[k] = -1
linkKey = &k
}
}
entry.ReadAttributes(top)
if excludeByAttribute && entry.Attributes != nil && excludedByAttribute(*entry.Attributes) {