vfs, cmount: make truncate work properly in the presence or otherwise of open files

This commit is contained in:
Nick Craig-Wood 2017-11-16 09:31:33 +00:00
parent 94adf4f43b
commit dec21ccf63
4 changed files with 104 additions and 39 deletions

View file

@ -319,19 +319,6 @@ func (fsys *FS) Truncate(path string, size int64, fh uint64) (errc int) {
if errc != 0 { if errc != 0 {
return errc return errc
} }
// Read the size so far
var currentSize int64
if handle != nil {
fi, err := handle.Stat()
if err != nil {
return translateError(err)
}
currentSize = fi.Size()
} else {
currentSize = node.Size()
}
fs.Debugf(path, "truncate to %d, currentSize %d", size, currentSize)
if currentSize != size {
var err error var err error
if handle != nil { if handle != nil {
err = handle.Truncate(size) err = handle.Truncate(size)
@ -341,7 +328,6 @@ func (fsys *FS) Truncate(path string, size int64, fh uint64) (errc int) {
if err != nil { if err != nil {
return translateError(err) return translateError(err)
} }
}
return 0 return 0
} }

View file

@ -19,7 +19,7 @@ type File struct {
mu sync.RWMutex // protects the following mu sync.RWMutex // protects the following
o fs.Object // NB o may be nil if file is being written o fs.Object // NB o may be nil if file is being written
leaf string // leaf name of the object leaf string // leaf name of the object
writers int // number of writers for this file writers []Handle // writers for this file
pendingModTime time.Time // will be applied once o becomes available, i.e. after file was written pendingModTime time.Time // will be applied once o becomes available, i.e. after file was written
} }
@ -90,10 +90,28 @@ func (f *File) rename(d *Dir, o fs.Object) {
f.mu.Unlock() f.mu.Unlock()
} }
// addWriters increments or decrements the writers // addWriter adds a write handle to the file
func (f *File) addWriters(n int) { func (f *File) addWriter(h Handle) {
f.mu.Lock() f.mu.Lock()
f.writers += n f.writers = append(f.writers, h)
f.mu.Unlock()
}
// delWriter removes a write handle from the file
func (f *File) delWriter(h Handle) {
f.mu.Lock()
var found = -1
for i := range f.writers {
if f.writers[i] == h {
found = i
break
}
}
if found >= 0 {
f.writers = append(f.writers[:found], f.writers[found+1:]...)
} else {
fs.Debugf(f.o, "File.delWriter couldn't find handle")
}
f.mu.Unlock() f.mu.Unlock()
} }
@ -106,7 +124,7 @@ func (f *File) ModTime() (modTime time.Time) {
if !f.d.vfs.Opt.NoModTime { if !f.d.vfs.Opt.NoModTime {
// if o is nil it isn't valid yet or there are writers, so return the size so far // if o is nil it isn't valid yet or there are writers, so return the size so far
if f.o == nil || f.writers != 0 { if f.o == nil || len(f.writers) != 0 {
if !f.pendingModTime.IsZero() { if !f.pendingModTime.IsZero() {
return f.pendingModTime return f.pendingModTime
} }
@ -124,7 +142,7 @@ func (f *File) Size() int64 {
defer f.mu.Unlock() defer f.mu.Unlock()
// if o is nil it isn't valid yet or there are writers, so return the size so far // if o is nil it isn't valid yet or there are writers, so return the size so far
if f.o == nil || f.writers != 0 { if f.o == nil || len(f.writers) != 0 {
return atomic.LoadInt64(&f.size) return atomic.LoadInt64(&f.size)
} }
return f.o.Size() return f.o.Size()
@ -188,6 +206,13 @@ func (f *File) setObject(o fs.Object) {
f.d.addObject(f) f.d.addObject(f)
} }
// exists returns whether the file exists already
func (f *File) exists() bool {
f.mu.Lock()
defer f.mu.Unlock()
return f.o != nil
}
// Wait for f.o to become non nil for a short time returning it or an // Wait for f.o to become non nil for a short time returning it or an
// error. Use when opening a read handle. // error. Use when opening a read handle.
// //
@ -196,12 +221,12 @@ func (f *File) waitForValidObject() (o fs.Object, err error) {
for i := 0; i < 50; i++ { for i := 0; i < 50; i++ {
f.mu.Lock() f.mu.Lock()
o = f.o o = f.o
writers := f.writers nwriters := len(f.writers)
f.mu.Unlock() f.mu.Unlock()
if o != nil { if o != nil {
return o, nil return o, nil
} }
if writers == 0 { if nwriters == 0 {
return nil, errors.New("can't open file - writer failed") return nil, errors.New("can't open file - writer failed")
} }
time.Sleep(100 * time.Millisecond) time.Sleep(100 * time.Millisecond)
@ -383,9 +408,40 @@ func (f *File) Open(flags int) (fd Handle, err error) {
} }
// Truncate changes the size of the named file. // Truncate changes the size of the named file.
func (f *File) Truncate(size int64) error { func (f *File) Truncate(size int64) (err error) {
if f.d.vfs.Opt.CacheMode >= CacheModeWrites { // make a copy of fh.writers with the lock held then unlock so
// we can call other file methods.
f.mu.Lock()
writers := make([]Handle, len(f.writers))
copy(writers, f.writers)
f.mu.Unlock()
// If have writers then call truncate for each writer
if len(writers) != 0 {
fs.Debugf(f.o, "Truncating %d file handles", len(writers))
for _, h := range writers {
truncateErr := h.Truncate(size)
if truncateErr != nil {
err = truncateErr
} }
// FIXME }
return ENOSYS return err
}
fs.Debugf(f.o, "Truncating file")
// Otherwise if no writers then truncate the file by opening
// the file and truncating it.
flags := os.O_WRONLY
if size == 0 {
flags |= os.O_TRUNC
}
fh, err := f.Open(flags)
if err != nil {
return err
}
defer fs.CheckClose(fh, &err)
if size != 0 {
return fh.Truncate(size)
}
return nil
} }

View file

@ -52,6 +52,12 @@ func newRWFileHandle(d *Dir, f *File, remote string, flags int) (fh *RWFileHandl
flags: flags, flags: flags,
osPath: osPath, osPath: osPath,
} }
rdwrMode := fh.flags & accessModeMask
if rdwrMode != os.O_RDONLY {
fh.file.addWriter(fh)
}
return fh, nil return fh, nil
} }
@ -63,8 +69,6 @@ func (fh *RWFileHandle) openPending(truncate bool) (err error) {
return nil return nil
} }
rdwrMode := fh.flags & accessModeMask
// if not truncating the file, need to read it first // if not truncating the file, need to read it first
if fh.flags&os.O_TRUNC == 0 && !truncate { if fh.flags&os.O_TRUNC == 0 && !truncate {
// Fetch the file if it hasn't changed // Fetch the file if it hasn't changed
@ -92,9 +96,6 @@ func (fh *RWFileHandle) openPending(truncate bool) (err error) {
fh.file.setSize(0) fh.file.setSize(0)
} }
if rdwrMode != os.O_RDONLY {
fh.file.addWriters(1)
}
fs.Debugf(fh.remote, "Opening cached copy with flags=%s", decodeOpenFlags(fh.flags)) fs.Debugf(fh.remote, "Opening cached copy with flags=%s", decodeOpenFlags(fh.flags))
fd, err := os.OpenFile(fh.osPath, fh.flags|os.O_CREATE, 0600) fd, err := os.OpenFile(fh.osPath, fh.flags|os.O_CREATE, 0600)
if err != nil { if err != nil {
@ -140,6 +141,9 @@ func (fh *RWFileHandle) close() (err error) {
} }
fh.closed = true fh.closed = true
rdwrMode := fh.flags & accessModeMask rdwrMode := fh.flags & accessModeMask
if rdwrMode != os.O_RDONLY {
fh.file.delWriter(fh)
}
if !fh.opened { if !fh.opened {
// If read only then return // If read only then return
if rdwrMode == os.O_RDONLY { if rdwrMode == os.O_RDONLY {
@ -157,7 +161,6 @@ func (fh *RWFileHandle) close() (err error) {
} }
} }
if rdwrMode != os.O_RDONLY { if rdwrMode != os.O_RDONLY {
fh.file.addWriters(-1)
fi, err := fh.File.Stat() fi, err := fh.File.Stat()
if err != nil { if err != nil {
fs.Errorf(fh.remote, "Failed to stat cache file: %v", err) fs.Errorf(fh.remote, "Failed to stat cache file: %v", err)

View file

@ -49,7 +49,7 @@ func newWriteFileHandle(d *Dir, f *File, remote string) (*WriteFileHandle, error
fh.o = o fh.o = o
fh.result <- err fh.result <- err
}() }()
fh.file.addWriters(1) fh.file.addWriter(fh)
fh.file.setSize(0) fh.file.setSize(0)
return fh, nil return fh, nil
} }
@ -129,6 +129,11 @@ func (fh *WriteFileHandle) Write(p []byte) (n int, err error) {
return fh.writeAt(p, fh.offset) return fh.writeAt(p, fh.offset)
} }
// WriteString a string to the file
func (fh *WriteFileHandle) WriteString(s string) (n int, err error) {
return fh.Write([]byte(s))
}
// Offset returns the offset of the file pointer // Offset returns the offset of the file pointer
func (fh *WriteFileHandle) Offset() (offset int64) { func (fh *WriteFileHandle) Offset() (offset int64) {
fh.mu.Lock() fh.mu.Lock()
@ -145,7 +150,7 @@ func (fh *WriteFileHandle) close() error {
return ECLOSED return ECLOSED
} }
fh.closed = true fh.closed = true
fh.file.addWriters(-1) fh.file.delWriter(fh)
writeCloseErr := fh.pipeWriter.Close() writeCloseErr := fh.pipeWriter.Close()
err := <-fh.result err := <-fh.result
if err == nil { if err == nil {
@ -228,3 +233,18 @@ func (fh *WriteFileHandle) Stat() (os.FileInfo, error) {
defer fh.mu.Unlock() defer fh.mu.Unlock()
return fh.file, nil return fh.file, nil
} }
// Truncate file to given size
func (fh *WriteFileHandle) Truncate(size int64) (err error) {
fh.mu.Lock()
defer fh.mu.Unlock()
if fh.closed {
return ECLOSED
}
if size != fh.offset {
fs.Errorf(fh.remote, "Truncate: Can't change size without cache")
return EPERM
}
// File is correct size
return nil
}