rclone/cmd/mount/file.go
Nick Craig-Wood a67688dcc7 mount,cmount,mount2: add --direct-io flag to force uncached access
This change adds the --direct-io flag to the mount. This means the
page cache is completely bypassed for reads and writes. No read-ahead
takes place. Shared mmap is disabled.

This is useful to accurately read files which may change length
frequently on the source.
2024-03-26 17:32:11 +00:00

132 lines
3.5 KiB
Go

//go:build linux
// +build linux
package mount
import (
"context"
"syscall"
"time"
"bazil.org/fuse"
fusefs "bazil.org/fuse/fs"
"github.com/rclone/rclone/fs/log"
"github.com/rclone/rclone/vfs"
)
// File represents a file
type File struct {
*vfs.File
fsys *FS
}
// Check interface satisfied
var _ fusefs.Node = (*File)(nil)
// Attr fills out the attributes for the file
func (f *File) Attr(ctx context.Context, a *fuse.Attr) (err error) {
defer log.Trace(f, "")("a=%+v, err=%v", a, &err)
a.Valid = f.fsys.opt.AttrTimeout
modTime := f.File.ModTime()
Size := uint64(f.File.Size())
Blocks := (Size + 511) / 512
a.Gid = f.VFS().Opt.GID
a.Uid = f.VFS().Opt.UID
a.Mode = f.VFS().Opt.FilePerms
a.Size = Size
a.Atime = modTime
a.Mtime = modTime
a.Ctime = modTime
a.Blocks = Blocks
return nil
}
// Check interface satisfied
var _ fusefs.NodeSetattrer = (*File)(nil)
// Setattr handles attribute changes from FUSE. Currently supports ModTime and Size only
func (f *File) Setattr(ctx context.Context, req *fuse.SetattrRequest, resp *fuse.SetattrResponse) (err error) {
defer log.Trace(f, "a=%+v", req)("err=%v", &err)
if !f.VFS().Opt.NoModTime {
if req.Valid.Mtime() {
err = f.File.SetModTime(req.Mtime)
} else if req.Valid.MtimeNow() {
err = f.File.SetModTime(time.Now())
}
}
if req.Valid.Size() {
err = f.File.Truncate(int64(req.Size))
}
return translateError(err)
}
// Check interface satisfied
var _ fusefs.NodeOpener = (*File)(nil)
// Open the file for read or write
func (f *File) Open(ctx context.Context, req *fuse.OpenRequest, resp *fuse.OpenResponse) (fh fusefs.Handle, err error) {
defer log.Trace(f, "flags=%v", req.Flags)("fh=%v, err=%v", &fh, &err)
// fuse flags are based off syscall flags as are os flags, so
// should be compatible
handle, err := f.File.Open(int(req.Flags))
if err != nil {
return nil, translateError(err)
}
// If size unknown then use direct io to read
if entry := handle.Node().DirEntry(); entry != nil && entry.Size() < 0 {
resp.Flags |= fuse.OpenDirectIO
}
if f.fsys.opt.DirectIO {
resp.Flags |= fuse.OpenDirectIO
}
return &FileHandle{handle}, nil
}
// Check interface satisfied
var _ fusefs.NodeFsyncer = (*File)(nil)
// Fsync the file
//
// Note that we don't do anything except return OK
func (f *File) Fsync(ctx context.Context, req *fuse.FsyncRequest) (err error) {
defer log.Trace(f, "")("err=%v", &err)
return nil
}
// Getxattr gets an extended attribute by the given name from the
// node.
//
// If there is no xattr by that name, returns fuse.ErrNoXattr.
func (f *File) Getxattr(ctx context.Context, req *fuse.GetxattrRequest, resp *fuse.GetxattrResponse) error {
return syscall.ENOSYS // we never implement this
}
var _ fusefs.NodeGetxattrer = (*File)(nil)
// Listxattr lists the extended attributes recorded for the node.
func (f *File) Listxattr(ctx context.Context, req *fuse.ListxattrRequest, resp *fuse.ListxattrResponse) error {
return syscall.ENOSYS // we never implement this
}
var _ fusefs.NodeListxattrer = (*File)(nil)
// Setxattr sets an extended attribute with the given name and
// value for the node.
func (f *File) Setxattr(ctx context.Context, req *fuse.SetxattrRequest) error {
return syscall.ENOSYS // we never implement this
}
var _ fusefs.NodeSetxattrer = (*File)(nil)
// Removexattr removes an extended attribute for the name.
//
// If there is no xattr by that name, returns fuse.ErrNoXattr.
func (f *File) Removexattr(ctx context.Context, req *fuse.RemovexattrRequest) error {
return syscall.ENOSYS // we never implement this
}
var _ fusefs.NodeRemovexattrer = (*File)(nil)