Go os.ReadDir reading files deleted in run time

Question

I have a program that is finding the larges files on a filesystem within the same directory. If I call FileDisplay.Delete function and then re-run GetTopXFiles on the directory, it returns files that had been deleted. Using ls while the program is still running, I can see that the files is no longer there. Interestingly, if I fallocate -l 251.2M file100 I can see my newly created file as being the largest file. If I then remove it using rm or the program, re-run the GetTopXFiles it still returns. If I restart the program it recognizes the file is gone.

package fileFinder

import (
    "fmt"
    "io"
    "io/fs"
    "log"
    "os"
    "sort"
    "sync"

    "github.com/google/fscrypt/filesystem"
    "github.com/sirupsen/logrus"
)

var device string

type fileDisplay struct {
    sync.RWMutex
    Files []FileDisplay
}

var files fileDisplay

type FileDisplay struct {
    Size int64  `json:"size"`
    Path string `json:"path"`
}
type bySize []FileDisplay

func (a bySize) Len() int           { return len(a) }
func (a bySize) Less(i, j int) bool { return a[i].Size < a[j].Size }
func (a bySize) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }

func GetTopXFiles(mountpoint string, limit int) ([]FileDisplay, error) {
    log.SetOutput(io.Discard)
    if mountpoint == "" {
        return nil, fmt.Errorf("Path cannot be empty")
    }
    if limit < 1 {
        return nil, fmt.Errorf("Limit must be 1 or greater")

    }
    if mountpoint[len(mountpoint)-1:] != "/" {
        mountpoint = mountpoint + "/"
    }
    mount, err := filesystem.FindMount(mountpoint)
    if err != nil {
        return nil, err
    }
    device = mount.Device

    entries, err := os.ReadDir(mountpoint)
    if err != nil {
        return nil, err
    }
    var wg sync.WaitGroup
    getFiles(mountpoint, entries, &wg)
    wg.Wait()
    sort.Sort(bySize(files.Files))
    var shortFiles []FileDisplay
    if len(files.Files) > limit {
        shortFiles = files.Files[len(files.Files)-limit:]
    } else {
        shortFiles = files.Files
    }

    return shortFiles, nil

}

func getFiles(start string, entries []fs.DirEntry, wg *sync.WaitGroup) {
    for _, entry := range entries {
        wg.Add(1)
        go handleEntry(start, entry, wg)
    }

}

func handleEntry(start string, entry fs.DirEntry, wg *sync.WaitGroup) {
    defer wg.Done()
    var file FileDisplay
    mount, err := filesystem.FindMount(start + entry.Name())
    if err != nil {
        logrus.Errorln(err, start+entry.Name())
        return
    }
    if mount.Device == device {
        if entry.Type().IsRegular() {
            fileInfo, err := os.Stat(start + entry.Name())
            if err != nil {
                logrus.Errorln(err, start+entry.Name())
                return
            }
            file.Path = start + entry.Name()
            file.Size = fileInfo.Size()
            files.Append(file)
        } else if entry.IsDir() {
            entries, err := os.ReadDir(start + entry.Name())
            if err != nil {
                logrus.Errorln(err, start+entry.Name())
                return
            }
            logrus.Info("Searching ", start+entry.Name())
            getFiles(start+entry.Name()+"/", entries, wg)
        }
    }

}

func (f *FileDisplay) DisplaySizeIEC() string {
    const unit = 1024
    b := f.Size
    if b < unit {
        return fmt.Sprintf("%dB", b)
    }
    div, exp := int64(unit), 0
    for n := b / unit; n >= unit; n /= unit {
        div *= unit
        exp++
    }
    return fmt.Sprintf("%.2f%ciB",
        float64(b)/float64(div), "KMGTPE"[exp])
}

func (f *FileDisplay) Delete() error {
    err := os.Remove(f.Path)
    if err != nil {
        return err
    }
    return nil
}

func (fd *fileDisplay) Append(item FileDisplay) {
    fd.Lock()
    defer fd.Unlock()

    fd.Files = append(fd.Files, item)
}

Answer 1

var files fileDisplay

files is a global fileDisplay which contains a []FileDisplay that gets filled in by GetTopXFiles . But nothing updates files even if Delete is called. Thus, files is out of date after a delete, containing files that were since deleted.

The easiest solution is to not use a global files but instead regenerate one within GetTopXFiles .