ANDROID: fuse-bpf: Support FUSE_STATFS

Adds support for FUSE_STATFS, needed to run various filesystem tests

Bug: 217570523
Test: bpf_test_statfs
Change-Id: I5ee13e880118c5c79c4ca17bb2e902a3e17a7eb8
Signed-off-by: Daniel Rosenberg <drosen@google.com>

fs/fuse/backing.c

@@ -1786,6 +1786,56 @@ void *fuse_setattr_finalize(struct fuse_args *fa,
 	return NULL;
 }
 
+int fuse_statfs_initialize(
+		struct fuse_args *fa, struct fuse_statfs_out *fso,
+		struct dentry *dentry, struct kstatfs *buf)
+{
+	*fso = (struct fuse_statfs_out) {0};
+	*fa = (struct fuse_args) {
+		.nodeid = get_node_id(d_inode(dentry)),
+		.opcode = FUSE_STATFS,
+		.out_numargs = 1,
+		.out_numargs = 1,
+		.out_args[0].size = sizeof(fso),
+		.out_args[0].value = fso,
+	};
+
+	return 0;
+}
+
+int fuse_statfs_backing(
+		struct fuse_args *fa,
+		struct dentry *dentry, struct kstatfs *buf)
+{
+	int err = 0;
+	struct path backing_path;
+	struct fuse_statfs_out *fso = fa->out_args[0].value;
+
+	get_fuse_backing_path(dentry, &backing_path);
+	if (!backing_path.dentry)
+		return -EBADF;
+	err = vfs_statfs(&backing_path, buf);
+	path_put(&backing_path);
+	buf->f_type = FUSE_SUPER_MAGIC;
+
+	//TODO Provide postfilter opportunity to modify
+	if (!err)
+		convert_statfs_to_fuse(&fso->st, buf);
+
+	return err;
+}
+
+void *fuse_statfs_finalize(
+		struct fuse_args *fa,
+		struct dentry *dentry, struct kstatfs *buf)
+{
+	struct fuse_statfs_out *fso = fa->out_args[0].value;
+
+	if (!fa->error_in)
+		convert_fuse_statfs(buf, &fso->st);
+	return NULL;
+}
+
 int fuse_get_link_initialize(struct fuse_args *fa, struct fuse_dummy_io *unused,
 		struct inode *inode, struct dentry *dentry,
 		struct delayed_call *callback, const char **out)

fs/fuse/fuse_i.h

@@ -33,6 +33,9 @@
 #include <linux/pid_namespace.h>
 #include <linux/refcount.h>
 #include <linux/user_namespace.h>
+#include <linux/statfs.h>
+
+#define FUSE_SUPER_MAGIC 0x65735546
 
 /** Default max number of pages that can be used in a single read request */
 #define FUSE_DEFAULT_MAX_PAGES_PER_REQ 32
@@ -1567,6 +1570,13 @@ int fuse_setattr_backing(struct fuse_args *fa,
 void *fuse_setattr_finalize(struct fuse_args *fa,
 		struct dentry *dentry, struct iattr *attr, struct file *file);
 
+int fuse_statfs_initialize(struct fuse_args *fa, struct fuse_statfs_out *fso,
+		struct dentry *dentry, struct kstatfs *buf);
+int fuse_statfs_backing(struct fuse_args *fa,
+		struct dentry *dentry, struct kstatfs *buf);
+void *fuse_statfs_finalize(struct fuse_args *fa,
+		struct dentry *dentry, struct kstatfs *buf);
+
 int fuse_get_link_initialize(struct fuse_args *fa, struct fuse_dummy_io *dummy,
 		struct inode *inode, struct dentry *dentry,
 		struct delayed_call *callback, const char **out);
@@ -1708,6 +1718,33 @@ static inline int finalize_attr(struct inode *inode, struct fuse_attr_out *outar
 	return err;
 }
 
+static inline void convert_statfs_to_fuse(struct fuse_kstatfs *attr, struct kstatfs *stbuf)
+{
+	attr->bsize   = stbuf->f_bsize;
+	attr->frsize  = stbuf->f_frsize;
+	attr->blocks  = stbuf->f_blocks;
+	attr->bfree   = stbuf->f_bfree;
+	attr->bavail  = stbuf->f_bavail;
+	attr->files   = stbuf->f_files;
+	attr->ffree   = stbuf->f_ffree;
+	attr->namelen = stbuf->f_namelen;
+	/* fsid is left zero */
+}
+
+static inline void convert_fuse_statfs(struct kstatfs *stbuf, struct fuse_kstatfs *attr)
+{
+	stbuf->f_type    = FUSE_SUPER_MAGIC;
+	stbuf->f_bsize   = attr->bsize;
+	stbuf->f_frsize  = attr->frsize;
+	stbuf->f_blocks  = attr->blocks;
+	stbuf->f_bfree   = attr->bfree;
+	stbuf->f_bavail  = attr->bavail;
+	stbuf->f_files   = attr->files;
+	stbuf->f_ffree   = attr->ffree;
+	stbuf->f_namelen = attr->namelen;
+	/* fsid is left zero */
+}
+
 #ifdef CONFIG_FUSE_BPF
 struct fuse_err_ret {
 	void *result;

fs/fuse/inode.c

@@ -50,8 +50,6 @@ MODULE_PARM_DESC(max_user_congthresh,
  "Global limit for the maximum congestion threshold an "
  "unprivileged user can set");
 
-#define FUSE_SUPER_MAGIC 0x65735546
-
 #define FUSE_DEFAULT_BLKSIZE 512
 
 /** Maximum number of outstanding background requests */
@@ -549,20 +547,6 @@ static void fuse_put_super(struct super_block *sb)
 	fuse_mount_put(fm);
 }
 
-static void convert_fuse_statfs(struct kstatfs *stbuf, struct fuse_kstatfs *attr)
-{
-	stbuf->f_type    = FUSE_SUPER_MAGIC;
-	stbuf->f_bsize   = attr->bsize;
-	stbuf->f_frsize  = attr->frsize;
-	stbuf->f_blocks  = attr->blocks;
-	stbuf->f_bfree   = attr->bfree;
-	stbuf->f_bavail  = attr->bavail;
-	stbuf->f_files   = attr->files;
-	stbuf->f_ffree   = attr->ffree;
-	stbuf->f_namelen = attr->namelen;
-	/* fsid is left zero */
-}
-
 static int fuse_statfs(struct dentry *dentry, struct kstatfs *buf)
 {
 	struct super_block *sb = dentry->d_sb;
@@ -570,12 +554,24 @@ static int fuse_statfs(struct dentry *dentry, struct kstatfs *buf)
 	FUSE_ARGS(args);
 	struct fuse_statfs_out outarg;
 	int err;
+#ifdef CONFIG_FUSE_BPF
+	struct fuse_err_ret fer;
+#endif
 
 	if (!fuse_allow_current_process(fm->fc)) {
 		buf->f_type = FUSE_SUPER_MAGIC;
 		return 0;
 	}
 
+#ifdef CONFIG_FUSE_BPF
+	fer = fuse_bpf_backing(dentry->d_inode, struct fuse_statfs_out,
+			       fuse_statfs_initialize, fuse_statfs_backing,
+			       fuse_statfs_finalize,
+			       dentry, buf);
+	if (fer.ret)
+		return PTR_ERR(fer.result);
+#endif
+
 	memset(&outarg, 0, sizeof(outarg));
 	args.in_numargs = 0;
 	args.opcode = FUSE_STATFS;

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

@@ -16,6 +16,7 @@
 
 #include <sys/mount.h>
 #include <sys/stat.h>
+#include <sys/statfs.h>
 #include <sys/xattr.h>
 
 #include <linux/unistd.h>
@@ -302,6 +303,20 @@ int s_stat(struct s pathname, struct stat *st)
 	return res;
 }
 
+int s_statfs(struct s pathname, struct statfs *st)
+{
+	int res;
+
+	if (!pathname.s) {
+		errno = ENOMEM;
+		return -1;
+	}
+
+	res = statfs(pathname.s, st);
+	free(pathname.s);
+	return res;
+}
+
 DIR *s_opendir(struct s pathname)
 {
 	DIR *res;

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

@@ -284,6 +284,11 @@ int trace_daemon(struct fuse_args *fa)
 		return FUSE_BPF_BACKING;
 	}
 
+	case FUSE_STATFS | FUSE_PREFILTER: {
+		bpf_printk("statfs %d", fa->nodeid);
+		return FUSE_BPF_BACKING;
+	}
+
 	default:
 		if (fa->opcode & FUSE_PREFILTER)
 			bpf_printk("prefilter *** UNKNOWN *** opcode: %d",

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

@@ -1422,6 +1422,34 @@ out:
 	return result;
 }
 
+static int bpf_test_statfs(const char *mount_dir)
+{
+	int result = TEST_FAILURE;
+	int src_fd = -1;
+	int bpf_fd = -1;
+	int fuse_dev = -1;
+	int fd = -1;
+	struct statfs st;
+
+	TEST(src_fd = open(ft_src, O_DIRECTORY | O_RDONLY | O_CLOEXEC),
+	     src_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);
+
+	TESTSYSCALL(s_statfs(s(mount_dir), &st));
+	TESTEQUAL(bpf_test_trace("statfs"), 0);
+	TESTEQUAL(st.f_type, 0x65735546);
+	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;
@@ -1524,6 +1552,7 @@ int main(int argc, char *argv[])
 		MAKE_TEST(mmap_test),
 		MAKE_TEST(readdir_perms_test),
 		MAKE_TEST(inotify_test),
+		MAKE_TEST(bpf_test_statfs),
 	};
 #undef MAKE_TEST
 

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

@@ -341,6 +341,11 @@ int trace_test(struct fuse_args *fa)
 		return FUSE_BPF_BACKING;
 	}
 
+	case FUSE_STATFS | FUSE_PREFILTER: {
+		bpf_printk("statfs");
+		return FUSE_BPF_BACKING;
+	}
+
 	default:
 		bpf_printk("Unknown opcode %d", fa->opcode);
 		return 0;

tools/testing/selftests/filesystems/fuse/test_fuse.h

@@ -12,6 +12,7 @@
 
 #include <dirent.h>
 #include <sys/stat.h>
+#include <sys/statfs.h>
 #include <sys/types.h>
 
 #define PAGE_SIZE 4096
@@ -50,6 +51,7 @@ int s_openat(int dirfd, struct s pathname, int flags, ...);
 int s_creat(struct s pathname, mode_t mode);
 int s_mkfifo(struct s pathname, mode_t mode);
 int s_stat(struct s pathname, struct stat *st);
+int s_statfs(struct s pathname, struct statfs *st);
 DIR *s_opendir(struct s pathname);
 int s_getxattr(struct s pathname, const char name[], void *value, size_t size,
 	       ssize_t *ret_size);