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cmount: add support for reading unknown length files using direct IO 

This means that on Linux and OSX at least reading a google doc from a
mount will behave sensibly.
This commit is contained in:
Nick Craig-Wood 2020-05-07 11:55:56 +01:00
parent 0ee16b51c4
commit 1222b78ec4
1 changed files with 56 additions and 23 deletions
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79
cmd/cmount/fs.go
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@ -289,41 +289,65 @@ func (fsys *FS) Statfs(path string, stat *fuse.Statfs_t) (errc int) {
return 0
}
// Open opens a file
func (fsys *FS) Open(path string, flags int) (errc int, fh uint64) {
defer log.Trace(path, "flags=0x%X", flags)("errc=%d, fh=0x%X", &errc, &fh)
// OpenEx opens a file
func (fsys *FS) OpenEx(path string, fi *fuse.FileInfo_t) (errc int) {
defer log.Trace(path, "flags=0x%X", fi.Flags)("errc=%d, fh=0x%X", &errc, &fi.Fh)
fi.Fh = fhUnset
// translate the fuse flags to os flags
flags = translateOpenFlags(flags)
flags := translateOpenFlags(fi.Flags)
handle, err := fsys.VFS.OpenFile(path, flags, 0777)
if err != nil {
return translateError(err), fhUnset
return translateError(err)
}
// FIXME add support for unknown length files setting direct_io
// See: https://github.com/billziss-gh/cgofuse/issues/38
// If size unknown then use direct io to read
if entry := handle.Node().DirEntry(); entry != nil && entry.Size() < 0 {
fi.DirectIo = true
}
return 0, fsys.openHandle(handle)
fi.Fh = fsys.openHandle(handle)
return 0
}
// Open opens a file
func (fsys *FS) Open(path string, flags int) (errc int, fh uint64) {
var fi = fuse.FileInfo_t{
Flags: flags,
}
errc = fsys.OpenEx(path, &fi)
return errc, fi.Fh
}
// CreateEx creates and opens a file.
func (fsys *FS) CreateEx(filePath string, mode uint32, fi *fuse.FileInfo_t) (errc int) {
defer log.Trace(filePath, "flags=0x%X, mode=0%o", fi.Flags, mode)("errc=%d, fh=0x%X", &errc, &fi.Fh)
fi.Fh = fhUnset
leaf, parentDir, errc := fsys.lookupParentDir(filePath)
if errc != 0 {
return errc
}
file, err := parentDir.Create(leaf, fi.Flags)
if err != nil {
return translateError(err)
}
// translate the fuse flags to os flags
flags := translateOpenFlags(fi.Flags) | os.O_CREATE
handle, err := file.Open(flags)
if err != nil {
return translateError(err)
}
fi.Fh = fsys.openHandle(handle)
return 0
}
// Create creates and opens a file.
func (fsys *FS) Create(filePath string, flags int, mode uint32) (errc int, fh uint64) {
defer log.Trace(filePath, "flags=0x%X, mode=0%o", flags, mode)("errc=%d, fh=0x%X", &errc, &fh)
leaf, parentDir, errc := fsys.lookupParentDir(filePath)
if errc != 0 {
return errc, fhUnset
var fi = fuse.FileInfo_t{
Flags: flags,
}
file, err := parentDir.Create(leaf, flags)
if err != nil {
return translateError(err), fhUnset
}
// translate the fuse flags to os flags
flags = translateOpenFlags(flags) | os.O_CREATE
handle, err := file.Open(flags)
if err != nil {
return translateError(err), fhUnset
}
return 0, fsys.openHandle(handle)
errc = fsys.CreateEx(filePath, mode, &fi)
return errc, fi.Fh
}
// Truncate truncates a file to size
@ -594,3 +618,12 @@ func translateOpenFlags(inFlags int) (outFlags int) {
// NB O_SYNC isn't defined by fuse
return outFlags
}
// Make sure interfaces are satisfied
var (
_ fuse.FileSystemInterface = (*FS)(nil)
_ fuse.FileSystemOpenEx = (*FS)(nil)
//_ fuse.FileSystemChflags = (*FS)(nil)
//_ fuse.FileSystemSetcrtime = (*FS)(nil)
//_ fuse.FileSystemSetchgtime = (*FS)(nil)
)