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mountlib: on read only open of file, make open pending until first read

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This fixes a problem with Windows which seems fond of opening files
just to read their attributes and closing them again.
This commit is contained in:
Nick Craig-Wood 2017-05-11 08:33:45 +01:00
parent 79aa060e21
commit 8be8a8e41b
1 changed files with 27 additions and 6 deletions
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33
cmd/mountlib/read.go
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@ -19,15 +19,12 @@ type ReadFileHandle struct {
noSeek bool
file *File
hash *fs.MultiHasher
opened bool
}
func newReadFileHandle(f *File, o fs.Object) (*ReadFileHandle, error) {
r, err := o.Open()
if err != nil {
return nil, err
}
var hash *fs.MultiHasher
var err error
if !f.d.fsys.noChecksum {
hash, err = fs.NewMultiHasherTypes(o.Fs().Hashes())
if err != nil {
@ -37,7 +34,6 @@ func newReadFileHandle(f *File, o fs.Object) (*ReadFileHandle, error) {
fh := &ReadFileHandle{
o: o,
r: fs.NewAccount(r, o).WithBuffer(), // account the transfer
noSeek: f.d.fsys.noSeek,
file: f,
hash: hash,
@ -46,6 +42,21 @@ func newReadFileHandle(f *File, o fs.Object) (*ReadFileHandle, error) {
return fh, nil
}
// openPending opens the file if there is a pending open
// call with the lock held
func (fh *ReadFileHandle) openPending() (err error) {
if fh.opened {
return nil
}
r, err := fh.o.Open()
if err != nil {
return err
}
fh.r = fs.NewAccount(r, fh.o).WithBuffer() // account the transfer
fh.opened = true
return nil
}
// String converts it to printable
func (fh *ReadFileHandle) String() string {
if fh == nil {
@ -106,6 +117,10 @@ func (fh *ReadFileHandle) seek(offset int64, reopen bool) (err error) {
func (fh *ReadFileHandle) Read(reqSize, reqOffset int64) (respData []byte, err error) {
fh.mu.Lock()
defer fh.mu.Unlock()
err = fh.openPending() // FIXME pending open could be more efficient in the presense of seek (and retried)
if err != nil {
return nil, err
}
// fs.Debugf(fh.o, "ReadFileHandle.Read size %d offset %d", reqSize, reqOffset)
if fh.closed {
fs.Errorf(fh.o, "ReadFileHandle.Read error: %v", EBADF)
@ -220,6 +235,9 @@ func (fh *ReadFileHandle) close() error {
func (fh *ReadFileHandle) Flush() error {
fh.mu.Lock()
defer fh.mu.Unlock()
if !fh.opened {
return nil
}
// fs.Debugf(fh.o, "ReadFileHandle.Flush")
if err := fh.checkHash(); err != nil {
@ -238,6 +256,9 @@ func (fh *ReadFileHandle) Flush() error {
func (fh *ReadFileHandle) Release() error {
fh.mu.Lock()
defer fh.mu.Unlock()
if !fh.opened {
return nil
}
if fh.closed {
fs.Debugf(fh.o, "ReadFileHandle.Release nothing to do")
return nil