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authorJakob Unterwurzacher2016-07-01 09:23:04 +0200
committerJakob Unterwurzacher2016-07-01 09:23:04 +0200
commitae77d1852793c4dd43c8ddd69de574223aecce5e (patch)
treed2e018f37f9eef077cd009a4c33691e5ade1148a /internal/fusefrontend/file.go
parente994ffa27d5c27c7502f657f6d2de2e105aaaa09 (diff)
fusefrontend: better comments for Truncate
Diffstat (limited to 'internal/fusefrontend/file.go')
-rw-r--r--internal/fusefrontend/file.go16
1 files changed, 10 insertions, 6 deletions
diff --git a/internal/fusefrontend/file.go b/internal/fusefrontend/file.go
index 546526b..513dbbf 100644
--- a/internal/fusefrontend/file.go
+++ b/internal/fusefrontend/file.go
@@ -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)