On Thu, Oct 1, 2026 at 5:09 PM Miklos Szeredi <[email protected]> wrote: > > Add backing_id_64 field to fuse_open_out to allow opening files with > 64-bit server-allocated backing IDs. > > When the server sets FUSE_BACKING_ID_64 in open_out.open_flags, the > kernel reads the backing ID from open_out.backing_id_64 instead of > open_out.backing_id. > > The open reply is now variable-length for backward compatibility with > servers that don't send the new backing_id_64 field. > > Signed-off-by: Miklos Szeredi <[email protected]>
Reviewed-by: Amir Goldstein <[email protected]> > --- > fs/fuse/dir.c | 3 ++- > fs/fuse/file.c | 6 +++++- > fs/fuse/fuse_i.h | 2 +- > fs/fuse/iomode.c | 34 ++++++++++++++++++++++++++++------ > fs/fuse/passthrough.c | 28 ++++++---------------------- > include/uapi/linux/fuse.h | 2 ++ > 6 files changed, 44 insertions(+), 31 deletions(-) > > diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c > index f48fafccce4b..874ec7cfffb1 100644 > --- a/fs/fuse/dir.c > +++ b/fs/fuse/dir.c > @@ -876,6 +876,7 @@ static int fuse_create_open(struct mnt_idmap *idmap, > struct inode *dir, > args.out_args[0].value = &outentry; > /* Store outarg for fuse_finish_open() */ > outopenp = &ff->args->open_outarg; > + args.out_argvar = true; /* compat */ > args.out_args[1].size = sizeof(*outopenp); > args.out_args[1].value = outopenp; > > @@ -885,7 +886,7 @@ static int fuse_create_open(struct mnt_idmap *idmap, > struct inode *dir, > > err = fuse_simple_idmap_request(idmap, fm, &args); > free_ext_value(&args); > - if (err) > + if (err < 0) > goto out_free_ff; > > err = -EIO; > diff --git a/fs/fuse/file.c b/fs/fuse/file.c > index 92976906ab05..1036c06fe35a 100644 > --- a/fs/fuse/file.c > +++ b/fs/fuse/file.c > @@ -28,6 +28,7 @@ static int fuse_send_open(struct fuse_mount *fm, u64 nodeid, > { > struct fuse_open_in inarg; > FUSE_ARGS(args); > + int res; > > memset(&inarg, 0, sizeof(inarg)); > inarg.flags = open_flags & ~(O_CREAT | O_EXCL | O_NOCTTY); > @@ -45,10 +46,13 @@ static int fuse_send_open(struct fuse_mount *fm, u64 > nodeid, > args.in_args[0].size = sizeof(inarg); > args.in_args[0].value = &inarg; > args.out_numargs = 1; > + args.out_argvar = true; /* compat */ > args.out_args[0].size = sizeof(*outargp); > args.out_args[0].value = outargp; > > - return fuse_simple_request(fm, &args); > + res = fuse_simple_request(fm, &args); > + > + return res < 0 ? res : 0; > } > > struct fuse_file *fuse_file_alloc(struct fuse_mount *fm, bool release) > diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h > index 003ef3c35d7a..59afebc3dd2b 100644 > --- a/fs/fuse/fuse_i.h > +++ b/fs/fuse/fuse_i.h > @@ -1314,7 +1314,7 @@ static inline struct fuse_backing > *fuse_inode_backing_set(struct fuse_inode *fi, > #endif > } > > -struct fuse_backing *fuse_passthrough_open(struct file *file, int > backing_id); > +int fuse_passthrough_open(struct file *file, struct fuse_backing *fb); > void fuse_passthrough_release(struct fuse_file *ff, struct fuse_backing *fb); > > static inline bool fuse_is_passthrough(struct fuse_file *ff) > diff --git a/fs/fuse/iomode.c b/fs/fuse/iomode.c > index 1a10bc65fb31..811ea603b776 100644 > --- a/fs/fuse/iomode.c > +++ b/fs/fuse/iomode.c > @@ -160,7 +160,9 @@ static int fuse_file_passthrough_open(struct inode > *inode, struct file *file) > { > struct fuse_file *ff = file->private_data; > struct fuse_conn *fc = get_fuse_conn(inode); > + struct fuse_open_out *outarg = &ff->args->open_outarg; > struct fuse_backing *fb; > + u64 backing_id; > int err; > > /* Check allowed conditions for file open in passthrough mode */ > @@ -170,18 +172,38 @@ static int fuse_file_passthrough_open(struct inode > *inode, struct file *file) > if (ff->open_flags & ~FOPEN_PASSTHROUGH_MASK) > return fuse_EIO("conflicting open flags"); > > - fb = fuse_passthrough_open(file, ff->args->open_outarg.backing_id); > - if (IS_ERR(fb)) > - return PTR_ERR(fb); > + if (!fc->backing_id_64) { > + if (outarg->backing_id_64 != 0) > + return fuse_EIO("64 bit backing ID set"); > + > + backing_id = outarg->backing_id; > + if (backing_id <= 0) > + return fuse_EIO("invalid backing ID"); > + } else { > + if (outarg->backing_id != 0) > + return fuse_EIO("32 bit backing ID set"); > + > + backing_id = outarg->backing_id_64; > + } > + fb = fuse_backing_lookup(fc, backing_id); > + if (!fb) > + return fuse_EIO("backing not found"); > + > + err = fuse_passthrough_open(file, fb); > + if (err) > + goto backing_put; > > /* First passthrough file open denies caching inode io mode */ > err = fuse_file_uncached_io_open(inode, ff, fb); > - if (!err) > - return 0; > + if (err) > + goto passthrough_release; > + > + return 0; > > +passthrough_release: > fuse_passthrough_release(ff, fb); > +backing_put: > fuse_backing_put(fb); > - > return err; > } > > diff --git a/fs/fuse/passthrough.c b/fs/fuse/passthrough.c > index 313c8d7ffc09..4894842ad6d0 100644 > --- a/fs/fuse/passthrough.c > +++ b/fs/fuse/passthrough.c > @@ -150,41 +150,25 @@ ssize_t fuse_passthrough_mmap(struct file *file, struct > vm_area_struct *vma) > > /* > * Setup passthrough to a backing file. > - * > - * Returns an fb object with elevated refcount to be stored in fuse inode. > */ > -struct fuse_backing *fuse_passthrough_open(struct file *file, int backing_id) > +int fuse_passthrough_open(struct file *file, struct fuse_backing *fb) > { > struct fuse_file *ff = file->private_data; > - struct fuse_conn *fc = ff->fm->fc; > - struct fuse_backing *fb = NULL; > struct file *backing_file; > > - if (fc->backing_id_64) > - return ERR_PTR(fuse_EIO("incompatible backing version")); > - > - if (backing_id <= 0) > - return ERR_PTR(fuse_EIO("invalid backing_id")); > - > - fb = fuse_backing_lookup(fc, backing_id); > - if (!fb) > - return ERR_PTR(fuse_EIO("backing not found")); > - > /* Allocate backing file per fuse file to store fuse path */ > backing_file = backing_file_open(file, file->f_flags, > &fb->file->f_path, fb->cred); > - if (IS_ERR(backing_file)) { > - fuse_backing_put(fb); > - return ERR_PTR(fuse_EIO("failed to open backing file (%ld)", > PTR_ERR(backing_file))); > - } > + if (IS_ERR(backing_file)) > + return fuse_EIO("failed to open backing file (%ld)", > PTR_ERR(backing_file)); > > ff->passthrough = backing_file; > ff->cred = get_cred(fb->cred); > > - pr_debug("%s: backing_id=%d, fb=0x%p, backing_file=0x%p\n", __func__, > - backing_id, fb, ff->passthrough); > + pr_debug("%s: backing_id=%llu, fb=0x%p, backing_file=0x%p\n", > __func__, > + fb->backing_id, fb, ff->passthrough); > > - return fb; > + return 0; > } > > void fuse_passthrough_release(struct fuse_file *ff, struct fuse_backing *fb) > diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h > index c88d7094af44..60fb2add5e12 100644 > --- a/include/uapi/linux/fuse.h > +++ b/include/uapi/linux/fuse.h > @@ -254,6 +254,7 @@ > * - add FUSE_PASSTHROUGH_V2 > * - add FUSE_DEV_IOC_BACKING_CREATE, struct fuse_backing_create_in > * - add FUSE_NOTIFY_BACKING_REMOVE, struct fuse_notify_backing_remove_out > + * - add backing_id_64 to fuse_open_out > */ > > #ifndef _LINUX_FUSE_H > @@ -841,6 +842,7 @@ struct fuse_open_out { > uint64_t fh; > uint32_t open_flags; > int32_t backing_id; > + uint64_t backing_id_64; > }; > > struct fuse_release_in { > -- > 2.54.0 >
