ANDROID: fuse-bpf: Support fuse_splice_read/write fully

Need to support fuse_splice_read and fuse_splice_write in both fuse bpf
and fuse passthrough modes.

Bug: 349258571
Test: fuse_test
Change-Id: I641b917d3decc4be1eea7ea39fac2b1f50c7e41b
Signed-off-by: Paul Lawrence <paullawrence@google.com>

fs/fuse/backing.c

@@ -1001,6 +1001,22 @@ ssize_t fuse_splice_read_backing(struct file *in, loff_t *ppos,
 	return ret;
 }
 
+ssize_t fuse_splice_write_backing(struct pipe_inode_info *pipe,
+		struct file *out, loff_t *ppos, size_t len, unsigned long flags)
+{
+	ssize_t ret;
+	struct fuse_file *ff = out->private_data;
+
+	inode_lock(file_inode(out));
+	file_start_write(ff->backing_file);
+	ret = iter_file_splice_write(pipe, ff->backing_file, ppos, len, flags);
+	file_end_write(ff->backing_file);
+	if (ret > 0)
+		fuse_copyattr(out, ff->backing_file);
+	inode_unlock(file_inode(out));
+	return ret;
+}
+
 long fuse_backing_ioctl(struct file *file, unsigned int command, unsigned long arg, int flags)
 {
 	struct fuse_file *ff = file->private_data;

fs/fuse/file.c

@@ -15,6 +15,7 @@
 #include <linux/sched.h>
 #include <linux/sched/signal.h>
 #include <linux/module.h>
+#include <linux/splice.h>
 #include <linux/swap.h>
 #include <linux/falloc.h>
 #include <linux/uio.h>
@@ -1843,9 +1844,9 @@ static ssize_t fuse_splice_read(struct file *in, loff_t *ppos,
 				struct pipe_inode_info *pipe, size_t len,
 				unsigned int flags)
 {
-#ifdef CONFIG_FUSE_BPF
 	struct fuse_file *ff = in->private_data;
 
+#ifdef CONFIG_FUSE_BPF
 	/* TODO - this is simply passthrough, not a proper BPF filter */
 	if (ff->backing_file)
 		return fuse_splice_read_backing(in, ppos, pipe, len, flags);
@@ -1863,6 +1864,12 @@ static ssize_t fuse_splice_write(struct pipe_inode_info *pipe, struct file *out,
 {
 	struct fuse_file *ff = out->private_data;
 
+#ifdef CONFIG_FUSE_BPF
+	/* TODO - this is simply passthrough, not a proper BPF filter */
+	if (ff->backing_file)
+		return fuse_splice_write_backing(pipe, out, ppos, len, flags);
+#endif
+
 	/* FOPEN_DIRECT_IO overrides FOPEN_PASSTHROUGH */
 	if (fuse_file_passthrough(ff) && !(ff->open_flags & FOPEN_DIRECT_IO))
 		return fuse_passthrough_splice_write(pipe, out, ppos, len, flags);

fs/fuse/fuse_i.h

@@ -1815,6 +1815,8 @@ void *fuse_file_write_iter_finalize(struct fuse_bpf_args *fa,
 
 ssize_t fuse_splice_read_backing(struct file *in, loff_t *ppos,
 		struct pipe_inode_info *pipe, size_t len, unsigned long flags);
+ssize_t fuse_splice_write_backing(struct pipe_inode_info *pipe,
+		struct file *out, loff_t *ppos, size_t len, unsigned long flags);
 
 long fuse_backing_ioctl(struct file *file, unsigned int command, unsigned long arg, int flags);
 

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

@@ -2114,6 +2114,60 @@ out:
 	return result;
 }
 
+static int splice_test(const char *mount_dir)
+{
+	const char *in_name = "in";
+	const char *out_name = "out";
+	const int splice_size = 4096;
+
+	int result = TEST_FAILURE;
+	int file_fd = -1;
+	int src_fd = -1;
+	int fuse_dev = -1;
+	int in_fd = -1;
+	int out_fd = -1;
+	int pipefd[2] = {-1, -1};
+
+	TEST(file_fd = s_creat(s_path(s(ft_src), s(in_name)), 0777),
+	     file_fd != -1);
+	TESTSYSCALL(fallocate(file_fd, 0, 0, splice_size));
+	TESTSYSCALL(close(file_fd));
+	file_fd = -1;
+
+	TEST(src_fd = open(ft_src, O_DIRECTORY | O_RDONLY | O_CLOEXEC),
+	     src_fd != -1);
+	TEST(fuse_dev = open("/dev/fuse", O_RDWR | O_CLOEXEC), fuse_dev != -1);
+	TESTEQUAL(mount_fuse(mount_dir, -1, src_fd, &fuse_dev), 0);
+
+	TESTSYSCALL(pipe(pipefd));
+	TEST(in_fd = s_open(s_path(s(mount_dir), s(in_name)), O_RDONLY),
+	     in_fd != -1);
+	TEST(out_fd = s_creat(s_path(s(mount_dir), s(out_name)), 0777),
+	     out_fd != -1);
+	TESTEQUAL(splice(in_fd, NULL, pipefd[1], NULL, splice_size, 0),
+		splice_size);
+	TESTEQUAL(splice(pipefd[0], NULL, out_fd, NULL, splice_size, 0),
+		splice_size);
+	TESTSYSCALL(close(in_fd));
+	in_fd = -1;
+	TESTSYSCALL(close(out_fd));
+	out_fd = -1;
+	TESTSYSCALL(close(pipefd[0]));
+	pipefd[0] = -1;
+	TESTSYSCALL(close(pipefd[1]));
+	pipefd[1] = -1;
+	result = TEST_SUCCESS;
+out:
+	umount(mount_dir);
+	close(fuse_dev);
+	close(src_fd);
+	close(in_fd);
+	close(out_fd);
+	close(pipefd[0]);
+	close(pipefd[1]);
+	return result;
+}
+
 /**
  * Test that fuse passthrough correctly traverses a mount point on the lower fs
  */
@@ -2288,6 +2342,7 @@ int main(int argc, char *argv[])
 		MAKE_TEST(bpf_test_create_and_remove_bpf),
 		MAKE_TEST(bpf_test_mkdir_and_remove_bpf),
 		MAKE_TEST(bpf_test_readahead),
+		MAKE_TEST(splice_test),
 		MAKE_TEST(bpf_test_follow_mounts),
 	};
 #undef MAKE_TEST