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libgocryptfs
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fusefrontend: better comments for Truncate

This commit is contained in:
Jakob Unterwurzacher 2016-07-01 09:23:04 +02:00
parent e994ffa27d
commit ae77d18527
1 changed files with 10 additions and 6 deletions
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16
internal/fusefrontend/file.go
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@ -396,7 +396,6 @@ func (f *file) Truncate(newSize uint64) fuse.Status {
// File grows
if newSize > oldSize {
// File was empty, create new header
if oldSize == 0 {
err = f.createHeader()
@ -404,10 +403,10 @@ func (f *file) Truncate(newSize uint64) fuse.Status {
return fuse.ToStatus(err)
}
}
blocks := f.contentEnc.ExplodePlainRange(oldSize, newSize-oldSize)
for _, b := range blocks {
// First and last block may be partial
// New blocks to add
addBlocks := f.contentEnc.ExplodePlainRange(oldSize, newSize-oldSize)
for _, b := range addBlocks {
// First and last block may be partial and must be actually written
if b.IsPartial() {
off, _ := b.PlaintextRange()
off += b.Skip
@ -416,6 +415,11 @@ func (f *file) Truncate(newSize uint64) fuse.Status {
return status
}
} else {
// Complete all-zero blocks can stay all-zero because we do file
// hole passthrough.
// TODO We are growing the file block-by-block which is pretty
// inefficient. We could coalesce all the grows into a single
// Ftruncate.
off, length := b.CiphertextRange()
err = syscall.Ftruncate(int(f.fd.Fd()), int64(off+length))
if err != nil {
@ -440,7 +444,7 @@ func (f *file) Truncate(newSize uint64) fuse.Status {
return status
}
}
// Truncate down to last complete block
// Truncate down to the last complete block
err = syscall.Ftruncate(int(f.fd.Fd()), int64(cipherOff))
if err != nil {
tlog.Warn.Printf("shrink Ftruncate returned error: %v", err)