ANDROID: fuse-bpf: support FUSE_LSEEK

Adds support for lseek via fuse-bpf

Bug: 224855060
Test: bpf_test_lseek
Signed-off-by: Daniel Rosenberg <drosen@google.com>
Change-Id: Ic282940d53b9bb44a291cb3a5dfe09847b4e5c9a

fs/fuse/backing.c

@@ -403,6 +403,65 @@ void *fuse_flush_finalize(struct fuse_args *fa, struct file *file, fl_owner_t id
 	return NULL;
 }
 
+int fuse_lseek_initialize(struct fuse_args *fa, struct fuse_lseek_io *flio,
+			  struct file *file, loff_t offset, int whence)
+{
+	struct fuse_file *fuse_file = file->private_data;
+
+	flio->fli = (struct fuse_lseek_in) {
+		.fh = fuse_file->fh,
+		.offset = offset,
+		.whence = whence,
+	};
+
+	*fa = (struct fuse_args) {
+		.nodeid = get_node_id(file->f_inode),
+		.opcode = FUSE_LSEEK,
+		.in_numargs = 1,
+		.in_args[0].size = sizeof(flio->fli),
+		.in_args[0].value = &flio->fli,
+		.out_numargs = 1,
+		.out_args[0].size = sizeof(flio->flo),
+		.out_args[0].value = &flio->flo,
+	};
+
+	return 0;
+}
+
+int fuse_lseek_backing(struct fuse_args *fa, struct file *file, loff_t offset, int whence)
+{
+	const struct fuse_lseek_in *fli = fa->in_args[0].value;
+	struct fuse_lseek_out *flo = fa->out_args[0].value;
+	struct fuse_file *fuse_file = file->private_data;
+	struct file *backing_file = fuse_file->backing_file;
+	loff_t ret;
+
+	/* TODO: Handle changing of the file handle */
+	if (offset == 0) {
+		if (whence == SEEK_CUR)
+			return file->f_pos;
+
+		if (whence == SEEK_SET)
+			return vfs_setpos(file, 0, 0);
+	}
+
+	inode_lock(file->f_inode);
+	backing_file->f_pos = file->f_pos;
+	ret = vfs_llseek(backing_file, fli->offset, fli->whence);
+	flo->offset = ret;
+	inode_unlock(file->f_inode);
+	return ret;
+}
+
+void *fuse_lseek_finalize(struct fuse_args *fa, struct file *file, loff_t offset, int whence)
+{
+	struct fuse_lseek_out *flo = fa->out_args[0].value;
+
+	if (!fa->error_in)
+		file->f_pos = flo->offset;
+	return ERR_PTR(flo->offset);
+}
+
 int fuse_copy_file_range_initialize(struct fuse_args *fa, struct fuse_copy_file_range_io *fcf,
 				   struct file *file_in, loff_t pos_in, struct file *file_out,
 				   loff_t pos_out, size_t len, unsigned int flags)

fs/fuse/file.c

@@ -2738,6 +2738,17 @@ static loff_t fuse_file_llseek(struct file *file, loff_t offset, int whence)
 {
 	loff_t retval;
 	struct inode *inode = file_inode(file);
+#ifdef CONFIG_FUSE_BPF
+	struct fuse_err_ret fer;
+
+	fer = fuse_bpf_backing(inode, struct fuse_lseek_io,
+			       fuse_lseek_initialize,
+			       fuse_lseek_backing,
+			       fuse_lseek_finalize,
+			       file, offset, whence);
+	if (fer.ret)
+		return PTR_ERR(fer.result);
+#endif
 
 	switch (whence) {
 	case SEEK_SET:

fs/fuse/fuse_i.h

@@ -1433,6 +1433,16 @@ int fuse_flush_backing(struct fuse_args *fa, struct file *file, fl_owner_t id);
 void *fuse_flush_finalize(struct fuse_args *fa,
 			  struct file *file, fl_owner_t id);
 
+struct fuse_lseek_io {
+	struct fuse_lseek_in fli;
+	struct fuse_lseek_out flo;
+};
+
+int fuse_lseek_initialize(struct fuse_args *fa, struct fuse_lseek_io *fli,
+			  struct file *file, loff_t offset, int whence);
+int fuse_lseek_backing(struct fuse_args *fa, struct file *file, loff_t offset, int whence);
+void *fuse_lseek_finalize(struct fuse_args *fa, struct file *file, loff_t offset, int whence);
+
 struct fuse_copy_file_range_io {
 	struct fuse_copy_file_range_in fci;
 	struct fuse_write_out fwo;

tools/testing/selftests/filesystems/fuse/fd_bpf.c

@@ -289,6 +289,13 @@ int trace_daemon(struct fuse_args *fa)
 		return FUSE_BPF_BACKING;
 	}
 
+	case FUSE_LSEEK | FUSE_PREFILTER: {
+		const struct fuse_lseek_in *fli = fa->in_args[0].value;
+
+		bpf_printk("lseek type:%d, offset:%lld", fli->whence, fli->offset);
+		return FUSE_BPF_BACKING;
+	}
+
 	default:
 		if (fa->opcode & FUSE_PREFILTER)
 			bpf_printk("prefilter *** UNKNOWN *** opcode: %d",

tools/testing/selftests/filesystems/fuse/fuse_test.c

@@ -1450,6 +1450,48 @@ out:
 	return result;
 }
 
+static int bpf_test_lseek(const char *mount_dir)
+{
+	const char *file = "real";
+	const char *test_data = "data";
+	int result = TEST_FAILURE;
+	int src_fd = -1;
+	int bpf_fd = -1;
+	int fuse_dev = -1;
+	int fd = -1;
+
+	TEST(src_fd = open(ft_src, O_DIRECTORY | O_RDONLY | O_CLOEXEC),
+	     src_fd != -1);
+	TEST(fd = openat(src_fd, file, O_CREAT | O_RDWR | O_CLOEXEC, 0777),
+	     fd != -1);
+	TESTEQUAL(write(fd, test_data, strlen(test_data)), strlen(test_data));
+	TESTSYSCALL(close(fd));
+	fd = -1;
+	TESTEQUAL(install_elf_bpf("test_bpf.bpf", "test_trace",
+				  &bpf_fd, NULL, NULL), 0);
+	TESTEQUAL(mount_fuse(mount_dir, bpf_fd, src_fd, &fuse_dev), 0);
+
+	TEST(fd = s_open(s_path(s(mount_dir), s(file)), O_RDONLY | O_CLOEXEC),
+	     fd != -1);
+	TESTEQUAL(lseek(fd, 3, SEEK_SET), 3);
+	TESTEQUAL(bpf_test_trace("lseek"), 0);
+	TESTEQUAL(lseek(fd, 5, SEEK_END), 9);
+	TESTEQUAL(bpf_test_trace("lseek"), 0);
+	TESTEQUAL(lseek(fd, 1, SEEK_CUR), 10);
+	TESTEQUAL(bpf_test_trace("lseek"), 0);
+	TESTEQUAL(lseek(fd, 1, SEEK_DATA), 1);
+	TESTEQUAL(bpf_test_trace("lseek"), 0);
+	result = TEST_SUCCESS;
+out:
+	close(fd);
+	umount(mount_dir);
+	close(fuse_dev);
+	close(bpf_fd);
+	close(src_fd);
+	return result;
+}
+
+
 static int parse_options(int argc, char *const *argv)
 {
 	signed char c;
@@ -1553,6 +1595,7 @@ int main(int argc, char *argv[])
 		MAKE_TEST(readdir_perms_test),
 		MAKE_TEST(inotify_test),
 		MAKE_TEST(bpf_test_statfs),
+		MAKE_TEST(bpf_test_lseek),
 	};
 #undef MAKE_TEST
 

tools/testing/selftests/filesystems/fuse/test_bpf.c

@@ -346,6 +346,13 @@ int trace_test(struct fuse_args *fa)
 		return FUSE_BPF_BACKING;
 	}
 
+	case FUSE_LSEEK | FUSE_PREFILTER: {
+		const struct fuse_lseek_in *fli = fa->in_args[0].value;
+
+		bpf_printk("lseek type:%d, offset:%lld", fli->whence, fli->offset);
+		return FUSE_BPF_BACKING;
+	}
+
 	default:
 		bpf_printk("Unknown opcode %d", fa->opcode);
 		return 0;