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libgocryptfs
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fusefrontend: doWrite: delete file header if first write fails 

xfstests generic/083 fills the filesystem almost completely while
running fsstress in parallel. In fsck, these would show up:

  readFileID 2580: incomplete file, got 18 instead of 19 bytes

This could happen when writing the file header works, but writing
the actual data fails.

Now we kill the header again by truncating the file to zero.
This commit is contained in:
Jakob Unterwurzacher 2018-07-15 14:14:12 +02:00
parent 55bb22bad6
commit c70df522d2
5 changed files with 88 additions and 37 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

96
internal/fusefrontend/file.go
View File

@ -122,9 +122,9 @@ func (f *File) createHeader() (fileID []byte, err error) {
if !f.fs.args.NoPrealloc {
err = syscallcompat.EnospcPrealloc(int(f.fd.Fd()), 0, contentenc.HeaderLen)
if err != nil {
// If the underlying filesystem is full, it is normal get ENOSPC here.
// Log at Info level instead of Warning.
tlog.Info.Printf("ino%d: createHeader: prealloc failed: %s\n", f.qIno.Ino, err.Error())
if !syscallcompat.IsENOSPC(err) {
tlog.Warn.Printf("ino%d: createHeader: prealloc failed: %s\n", f.qIno.Ino, err.Error())
}
return nil, err
}
}
@ -144,33 +144,41 @@ func (f *File) createHeader() (fileID []byte, err error) {
// returns the requested part of the plaintext.
//
// Called by Read() for normal reading,
// by Write() and Truncate() for Read-Modify-Write
func (f *File) doRead(dst []byte, off uint64, length uint64) ([]byte, fuse.Status) {
// Make sure we have the file ID.
f.fileTableEntry.HeaderLock.RLock()
if f.fileTableEntry.ID == nil {
f.fileTableEntry.HeaderLock.RUnlock()
// Yes, somebody else may take the lock before we can. This will get
// the header read twice, but causes no harm otherwise.
f.fileTableEntry.HeaderLock.Lock()
tmpID, err := f.readFileID()
if err == io.EOF {
f.fileTableEntry.HeaderLock.Unlock()
return nil, fuse.OK
}
if err != nil {
f.fileTableEntry.HeaderLock.Unlock()
tlog.Warn.Printf("doRead %d: corrupt header: %v", f.qIno.Ino, err)
return nil, fuse.EIO
}
f.fileTableEntry.ID = tmpID
// Downgrade the lock.
f.fileTableEntry.HeaderLock.Unlock()
// The file ID may change in here. This does no harm because we
// re-read it after the RLock().
// by Write() and Truncate() via doWrite() for Read-Modify-Write.
//
// doWrite() uses nolock=true because it makes sure the ID is in the cache and
// HeaderLock is locked before calling doRead.
func (f *File) doRead(dst []byte, off uint64, length uint64, nolock bool) ([]byte, fuse.Status) {
if !nolock {
// Make sure we have the file ID.
f.fileTableEntry.HeaderLock.RLock()
if f.fileTableEntry.ID == nil {
f.fileTableEntry.HeaderLock.RUnlock()
// Yes, somebody else may take the lock before we can. This will get
// the header read twice, but causes no harm otherwise.
f.fileTableEntry.HeaderLock.Lock()
tmpID, err := f.readFileID()
if err == io.EOF {
f.fileTableEntry.HeaderLock.Unlock()
return nil, fuse.OK
}
if err != nil {
f.fileTableEntry.HeaderLock.Unlock()
tlog.Warn.Printf("doRead %d: corrupt header: %v", f.qIno.Ino, err)
return nil, fuse.EIO
}
f.fileTableEntry.ID = tmpID
// Downgrade the lock.
f.fileTableEntry.HeaderLock.Unlock()
// The file ID may change in here. This does no harm because we
// re-read it after the RLock().
f.fileTableEntry.HeaderLock.RLock()
}
}
fileID := f.fileTableEntry.ID
if fileID == nil {
log.Panicf("filedID=%v, nolock=%v", fileID, nolock)
}
// Read the backing ciphertext in one go
blocks := f.contentEnc.ExplodePlainRange(off, length)
alignedOffset, alignedLength := blocks[0].JointCiphertextRange(blocks)
@ -182,7 +190,9 @@ func (f *File) doRead(dst []byte, off uint64, length uint64) ([]byte, fuse.Statu
ciphertext = ciphertext[:int(alignedLength)]
n, err := f.fd.ReadAt(ciphertext, int64(alignedOffset))
// We don't care if the file ID changes after we have read the data. Drop the lock.
f.fileTableEntry.HeaderLock.RUnlock()
if !nolock {
f.fileTableEntry.HeaderLock.RUnlock()
}
if err != nil && err != io.EOF {
tlog.Warn.Printf("read: ReadAt: %s", err.Error())
return nil, fuse.ToStatus(err)
@ -245,7 +255,7 @@ func (f *File) Read(buf []byte, off int64) (resultData fuse.ReadResult, code fus
if f.fs.args.SerializeReads {
serialize_reads.Wait(off, len(buf))
}
out, status := f.doRead(buf[:0], uint64(off), uint64(len(buf)))
out, status := f.doRead(buf[:0], uint64(off), uint64(len(buf)), false)
if f.fs.args.SerializeReads {
serialize_reads.Done()
}
@ -266,6 +276,7 @@ func (f *File) Read(buf []byte, off int64) (resultData fuse.ReadResult, code fus
//
// Empty writes do nothing and are allowed.
func (f *File) doWrite(data []byte, off int64) (uint32, fuse.Status) {
fileWasEmpty := false
// If the file ID is not cached, read it from disk
if f.fileTableEntry.ID == nil {
// Block other readers while we mess with the file header. Other writers
@ -275,13 +286,22 @@ func (f *File) doWrite(data []byte, off int64) (uint32, fuse.Status) {
// Write a new file header if the file is empty
if err == io.EOF {
tmpID, err = f.createHeader()
fileWasEmpty = true
}
if err != nil {
f.fileTableEntry.HeaderLock.Unlock()
return 0, fuse.ToStatus(err)
}
f.fileTableEntry.ID = tmpID
f.fileTableEntry.HeaderLock.Unlock()
if fileWasEmpty {
// The file was empty and we wrote a new file header. Keep the lock
// as we might have to kill the file header again if the data write
// fails.
defer f.fileTableEntry.HeaderLock.Unlock()
} else {
// We won't touch the header again, drop the lock immediately.
f.fileTableEntry.HeaderLock.Unlock()
}
}
// Handle payload data
dataBuf := bytes.NewBuffer(data)
@ -292,7 +312,7 @@ func (f *File) doWrite(data []byte, off int64) (uint32, fuse.Status) {
// Incomplete block -> Read-Modify-Write
if b.IsPartial() {
// Read
oldData, status := f.doRead(nil, b.BlockPlainOff(), f.contentEnc.PlainBS())
oldData, status := f.doRead(nil, b.BlockPlainOff(), f.contentEnc.PlainBS(), true)
if status != fuse.OK {
tlog.Warn.Printf("ino%d fh%d: RMW read failed: %s", f.qIno.Ino, f.intFd(), status.String())
return 0, status
@ -315,9 +335,17 @@ func (f *File) doWrite(data []byte, off int64) (uint32, fuse.Status) {
if !f.fs.args.NoPrealloc {
err = syscallcompat.EnospcPrealloc(int(f.fd.Fd()), cOff, int64(len(ciphertext)))
if err != nil {
// If the underlying filesystem is full, it is normal get ENOSPC here.
// Log at Info level instead of Warning.
tlog.Info.Printf("ino%d fh%d: doWrite: prealloc failed: %s", f.qIno.Ino, f.intFd(), err.Error())
if !syscallcompat.IsENOSPC(err) {
tlog.Warn.Printf("ino%d fh%d: doWrite: prealloc failed: %v", f.qIno.Ino, f.intFd(), err)
}
if fileWasEmpty {
// Kill the file header again
f.fileTableEntry.ID = nil
err2 := syscall.Ftruncate(int(f.fd.Fd()), 0)
if err2 != nil {
tlog.Warn.Printf("ino%d fh%d: doWrite: rollback failed: %v", f.qIno.Ino, f.intFd(), err2)
}
}
return 0, fuse.ToStatus(err)
}
}

2
internal/fusefrontend/file_allocate_truncate.go
View File

@ -144,7 +144,7 @@ func (f *File) Truncate(newSize uint64) fuse.Status {
var data []byte
if lastBlockLen > 0 {
var status fuse.Status
data, status = f.doRead(nil, plainOff, lastBlockLen)
data, status = f.doRead(nil, plainOff, lastBlockLen, false)
if status != fuse.OK {
tlog.Warn.Printf("Truncate: shrink doRead returned error: %v", err)
return status

1
internal/fusefrontend/file_holes.go
View File

@ -36,7 +36,6 @@ func (f *File) writePadHole(targetOff int64) fuse.Status {
// will contain a file hole in the ciphertext.
status := f.zeroPad(plainSize)
if status != fuse.OK {
tlog.Warn.Printf("zeroPad returned error %v", status)
return status
}
return fuse.OK

5
internal/nametransform/diriv.go
View File

@ -100,7 +100,10 @@ func WriteDirIV(dirfd *os.File, dir string) error {
_, err = fd.Write(iv)
if err != nil {
fd.Close()
tlog.Warn.Printf("WriteDirIV: Write: %v", err)
// It is normal to get ENOSPC here
if !syscallcompat.IsENOSPC(err) {
tlog.Warn.Printf("WriteDirIV: Write: %v", err)
}
// Delete incomplete gocryptfs.diriv file
syscallcompat.Unlinkat(int(dirfd.Fd()), file, 0)
return err

21
internal/syscallcompat/helpers.go Normal file
View File

@ -0,0 +1,21 @@
package syscallcompat
import (
"os"
"syscall"
)
// IsENOSPC tries to find out if "err" is a (potentially wrapped) ENOSPC error.
func IsENOSPC(err error) bool {
// syscallcompat.EnospcPrealloc returns the naked syscall error
if err == syscall.ENOSPC {
return true
}
// os.File.WriteAt returns &PathError
if err2, ok := err.(*os.PathError); ok {
if err2.Err == syscall.ENOSPC {
return true
}
}
return false
}