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authorJakob Unterwurzacher2021-05-29 16:00:40 +0200
committerJakob Unterwurzacher2021-05-29 16:00:40 +0200
commitc1d7e38761d35149f19524fa19d3afaaca73f302 (patch)
tree415295dfb899027ebb65c825d6b3349e8f107b0d /contrib
parent07164cbb3a42946a8bb0286da1bc7ea52bb33ee1 (diff)
findholes: add --create, --verify
Also, change the logic for the segment walk to not rely on the total size. cp does not use the total size either, and we miss bugs by cheating!
Diffstat (limited to 'contrib')
-rw-r--r--contrib/findholes/holes/holes.go119
-rw-r--r--contrib/findholes/main.go25
2 files changed, 130 insertions, 14 deletions
diff --git a/contrib/findholes/holes/holes.go b/contrib/findholes/holes/holes.go
index a2c16de..7d77ae1 100644
--- a/contrib/findholes/holes/holes.go
+++ b/contrib/findholes/holes/holes.go
@@ -4,7 +4,11 @@ package holes
import (
"fmt"
+ "log"
+ "math/rand"
+ "os"
"syscall"
+ "time"
)
const (
@@ -16,6 +20,19 @@ const (
SegmentEOF = SegmentType(102)
)
+type Whence int
+
+func (w Whence) String() string {
+ switch w {
+ case SEEK_DATA:
+ return "SEEK_DATA"
+ case SEEK_HOLE:
+ return "SEEK_HOLE"
+ default:
+ return "???"
+ }
+}
+
type Segment struct {
Offset int64
Type SegmentType
@@ -42,8 +59,11 @@ func (s SegmentType) String() string {
// PrettyPrint pretty-prints the Segments.
func PrettyPrint(segments []Segment) (out string) {
- for _, s := range segments {
- out += "\n" + s.String()
+ for i, s := range segments {
+ out += s.String()
+ if i < len(segments)-1 {
+ out += "\n"
+ }
}
return out
}
@@ -62,6 +82,7 @@ func Find(fd int) (segments []Segment, err error) {
// find out if file starts with data or hole
off, err := syscall.Seek(fd, 0, SEEK_DATA)
+ // starts with hole and has no data
if err == syscall.ENXIO {
segments = append(segments,
Segment{0, SegmentHole},
@@ -71,36 +92,108 @@ func Find(fd int) (segments []Segment, err error) {
if err != nil {
return nil, err
}
+ // starts with data
if off == cursor {
segments = append(segments, Segment{0, SegmentData})
} else {
+ // starts with hole
segments = append(segments,
Segment{0, SegmentHole},
- Segment{totalSize, SegmentData})
+ Segment{off, SegmentData})
cursor = off
}
// now we are at the start of data.
// find next hole, then next data, then next hole, then next data...
for {
- cursor, err = syscall.Seek(fd, cursor, SEEK_HOLE)
+ oldCursor := cursor
+ // Next hole
+ off, err = syscall.Seek(fd, cursor, SEEK_HOLE)
if err != nil {
return nil, err
}
- if cursor == totalSize {
- segments = append(segments, Segment{cursor, SegmentEOF})
- break
+ segments = append(segments, Segment{off, SegmentHole})
+ cursor = off
+
+ // Next data
+ off, err := syscall.Seek(fd, cursor, SEEK_DATA)
+ // No more data?
+ if err == syscall.ENXIO {
+ segments = append(segments,
+ Segment{totalSize, SegmentEOF})
+ return segments, nil
}
- segments = append(segments, Segment{cursor, SegmentHole})
- cursor, err = syscall.Seek(fd, cursor, SEEK_DATA)
if err != nil {
return nil, err
}
- if cursor == totalSize {
- segments = append(segments, Segment{cursor, SegmentEOF})
- break
+ segments = append(segments, Segment{off, SegmentData})
+ cursor = off
+
+ if oldCursor == cursor {
+ return nil, fmt.Errorf("%s\nerror: seek loop!", PrettyPrint(segments))
}
- segments = append(segments, Segment{cursor, SegmentData})
}
return segments, nil
}
+
+// Verify the gives `segments` using a full bytewise file scan
+func Verify(fd int, segments []Segment) (err error) {
+ last := segments[len(segments)-1]
+ if last.Type != SegmentEOF {
+ log.Panicf("BUG: last segment is not EOF. segments: %v", segments)
+ }
+
+ for i, s := range segments {
+ var whence int
+ switch s.Type {
+ case SegmentHole:
+ whence = SEEK_HOLE
+ case SegmentData:
+ whence = SEEK_DATA
+ case SegmentEOF:
+ continue
+ default:
+ log.Panicf("BUG: unkown segment type %d", s.Type)
+ }
+ for off := s.Offset; off < segments[i+1].Offset; off++ {
+ res, err := syscall.Seek(fd, off, whence)
+ if err != nil {
+ return fmt.Errorf("error: seek(%d, %s) returned error %v", off, Whence(whence).String(), err)
+ }
+ if res != off {
+ return fmt.Errorf("error: seek(%d, %s) returned new offset %d", off, Whence(whence).String(), res)
+ }
+ }
+ }
+ return err
+}
+
+// Create a test file at `path` with random holes
+func Create(path string) {
+ f, err := os.OpenFile(path, os.O_CREATE|os.O_EXCL|os.O_WRONLY, 0600)
+ if err != nil {
+ panic(err)
+ }
+ defer f.Close()
+
+ rand.Seed(time.Now().UnixNano())
+ offsets := make([]int64, 10)
+ for i := range offsets {
+ offsets[i] = int64(rand.Int31n(60000))
+ }
+
+ buf := []byte("x")
+ for _, off := range offsets {
+ _, err = f.WriteAt(buf, off)
+ if err != nil {
+ panic(err)
+ }
+ }
+
+ // Expand the file to 50000 bytes so we sometimes have a hole on the end
+ if offsets[len(offsets)-1] < 50000 {
+ f.Truncate(50000)
+ }
+
+ f.Sync()
+}
diff --git a/contrib/findholes/main.go b/contrib/findholes/main.go
index 6f1ae64..17597ae 100644
--- a/contrib/findholes/main.go
+++ b/contrib/findholes/main.go
@@ -10,13 +10,25 @@ import (
)
func main() {
+ flags := struct {
+ verify *bool
+ create *bool
+ }{}
+ flags.verify = flag.Bool("verify", false, "Verify results using full file scan")
+ flags.create = flag.Bool("create", false, "Create test file with random holes")
flag.Parse()
if flag.NArg() != 1 {
fmt.Printf("Usage: findholes FILE\n")
os.Exit(1)
}
- f, err := os.Open(flag.Arg(0))
+ path := flag.Arg(0)
+
+ if *flags.create {
+ holes.Create(path)
+ }
+
+ f, err := os.Open(path)
if err != nil {
// os.Open() gives nicer error messages than syscall.Open()
fmt.Println(err)
@@ -31,4 +43,15 @@ func main() {
}
fmt.Println(holes.PrettyPrint(segments))
+
+ if *flags.verify {
+ err = holes.Verify(int(f.Fd()), segments)
+ if err != nil {
+ fmt.Println(err)
+ os.Exit(1)
+ } else {
+ fmt.Println("verify ok")
+ }
+ }
+
}