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libgocryptfs
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Handle ENOSPC errors better by preallocating the space before writing 

Prevent the case that we run out of space in the middle of
writing a block - that would leave a corrupt block behind.
This commit is contained in:
Jakob Unterwurzacher 2015-11-08 22:36:29 +01:00
parent 8b83665693
commit fa3a382aa4
1 changed files with 16 additions and 5 deletions
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21
pathfs_frontend/file.go
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@ -194,6 +194,8 @@ func (f *file) Read(buf []byte, off int64) (resultData fuse.ReadResult, code fus
return fuse.ReadResultData(out), status
}
const FALLOC_FL_KEEP_SIZE = 0x01
// doWrite - encrypt "data" and write it to plaintext offset "off"
//
// Arguments do not have to be block-aligned, read-modify-write is
@ -238,16 +240,25 @@ func (f *file) doWrite(data []byte, off int64) (uint32, fuse.Status) {
}
// Write
blockOffset, _ := b.CiphertextRange()
blockOffset, blockLen := b.CiphertextRange()
blockData = f.cfs.EncryptBlock(blockData, b.BlockNo, f.header.Id)
cryptfs.Debug.Printf("ino%d: Writing %d bytes to block #%d, md5=%s\n",
f.ino, len(blockData)-cryptfs.BLOCK_OVERHEAD, b.BlockNo, cryptfs.Debug.Md5sum(blockData))
f.fdLock.Lock()
_, err := f.fd.WriteAt(blockData, int64(blockOffset))
f.fdLock.Unlock()
// Prevent partially written (=corrupt) blocks by preallocating the space beforehand
f.fdLock.Lock()
err := syscall.Fallocate(int(f.fd.Fd()), FALLOC_FL_KEEP_SIZE, int64(blockOffset), int64(blockLen))
f.fdLock.Unlock()
if err != nil {
cryptfs.Warn.Printf("Write failed: %s\n", err.Error())
cryptfs.Warn.Printf("doWrite: Fallocate failed: %s\n", err.Error())
status = fuse.ToStatus(err)
break
}
f.fdLock.Lock()
_, err = f.fd.WriteAt(blockData, int64(blockOffset))
f.fdLock.Unlock()
if err != nil {
cryptfs.Warn.Printf("doWrite: Write failed: %s\n", err.Error())
status = fuse.ToStatus(err)
break
}