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package fusefrontend
import (
"context"
"os"
"syscall"
"github.com/hanwen/go-fuse/v2/fs"
"github.com/hanwen/go-fuse/v2/fuse"
"github.com/rfjakob/gocryptfs/v2/internal/nametransform"
"github.com/rfjakob/gocryptfs/v2/internal/syscallcompat"
"github.com/rfjakob/gocryptfs/v2/internal/tlog"
)
// mangleOpenCreateFlags is used by Create() and Open() to convert the open flags the user
// wants to the flags we internally use to open the backing file using Openat().
// The returned flags always contain O_NOFOLLOW/O_SYMLINK.
func mangleOpenCreateFlags(flags uint32) (newFlags int) {
newFlags = int(flags)
// Convert WRONLY to RDWR. We always need read access to do read-modify-write cycles.
if (newFlags & syscall.O_ACCMODE) == syscall.O_WRONLY {
newFlags = newFlags ^ os.O_WRONLY | os.O_RDWR
}
// We also cannot open the file in append mode, we need to seek back for RMW
newFlags = newFlags &^ os.O_APPEND
// O_DIRECT accesses must be aligned in both offset and length. Due to our
// crypto header, alignment will be off, even if userspace makes aligned
// accesses. Running xfstests generic/013 on ext4 used to trigger lots of
// EINVAL errors due to missing alignment. Just fall back to buffered IO.
newFlags = newFlags &^ syscallcompat.O_DIRECT
// Create and Open are two separate FUSE operations, so O_CREAT should usually not
// be part of the Open() flags. Create() will add O_CREAT back itself.
newFlags = newFlags &^ syscall.O_CREAT
// We always want O_NOFOLLOW/O_SYMLINK to be safe against symlink races
newFlags |= syscallcompat.OpenatFlagNofollowSymlink
return newFlags
}
// Open - FUSE call. Open already-existing file.
//
// Symlink-safe through Openat().
func (n *Node) Open(ctx context.Context, flags uint32) (fh fs.FileHandle, fuseFlags uint32, errno syscall.Errno) {
dirfd, cName, errno := n.prepareAtSyscallMyself()
if errno != 0 {
return
}
defer syscall.Close(dirfd)
rn := n.rootNode()
newFlags := mangleOpenCreateFlags(flags)
// Taking this lock makes sure we don't race openWriteOnlyFile()
rn.openWriteOnlyLock.RLock()
defer rn.openWriteOnlyLock.RUnlock()
if rn.args.KernelCache {
fuseFlags = fuse.FOPEN_KEEP_CACHE
}
// Open backing file
fd, err := syscallcompat.Openat(dirfd, cName, newFlags, 0)
// Handle a few specific errors
if err != nil {
if err == syscall.EMFILE {
var lim syscall.Rlimit
syscall.Getrlimit(syscall.RLIMIT_NOFILE, &lim)
tlog.Warn.Printf("Open %q: too many open files. Current \"ulimit -n\": %d", cName, lim.Cur)
}
if err == syscall.EACCES && (int(flags)&syscall.O_ACCMODE) == syscall.O_WRONLY {
fd, err = rn.openWriteOnlyFile(dirfd, cName, newFlags)
}
}
// Could not handle the error? Bail out
if err != nil {
errno = fs.ToErrno(err)
return
}
fh, _, errno = NewFile(fd, cName, rn)
return fh, fuseFlags, errno
}
// Create - FUSE call. Creates a new file.
//
// Symlink-safe through the use of Openat().
func (n *Node) Create(ctx context.Context, name string, flags uint32, mode uint32, out *fuse.EntryOut) (inode *fs.Inode, fh fs.FileHandle, fuseFlags uint32, errno syscall.Errno) {
dirfd, cName, errno := n.prepareAtSyscall(name)
if errno != 0 {
return
}
defer syscall.Close(dirfd)
var err error
fd := -1
// Make sure context is nil if we don't want to preserve the owner
rn := n.rootNode()
if !rn.args.PreserveOwner {
ctx = nil
}
newFlags := mangleOpenCreateFlags(flags)
// Handle long file name
ctx2 := toFuseCtx(ctx)
if !rn.args.PlaintextNames && nametransform.IsLongContent(cName) {
// Create ".name"
err = rn.nameTransform.WriteLongNameAt(dirfd, cName, name)
if err != nil {
return nil, nil, 0, fs.ToErrno(err)
}
// Create content
fd, err = syscallcompat.OpenatUser(dirfd, cName, newFlags|syscall.O_CREAT|syscall.O_EXCL, mode, ctx2)
if err != nil {
nametransform.DeleteLongNameAt(dirfd, cName)
}
} else {
// Create content, normal (short) file name
fd, err = syscallcompat.OpenatUser(dirfd, cName, newFlags|syscall.O_CREAT|syscall.O_EXCL, mode, ctx2)
}
if err != nil {
// xfstests generic/488 triggers this
if err == syscall.EMFILE {
var lim syscall.Rlimit
syscall.Getrlimit(syscall.RLIMIT_NOFILE, &lim)
tlog.Warn.Printf("Create %q: too many open files. Current \"ulimit -n\": %d", cName, lim.Cur)
}
return nil, nil, 0, fs.ToErrno(err)
}
fh, st, errno := NewFile(fd, cName, rn)
if errno != 0 {
return
}
inode = n.newChild(ctx, st, out)
if rn.args.ForceOwner != nil {
out.Owner = *rn.args.ForceOwner
}
return inode, fh, fuseFlags, errno
}
|
