libfuse examples linked with OSXFUSE does not show up in Finder after mounted

pjhades

unread,

Jul 10, 2016, 4:53:00 PM7/10/16

to OSXFUSE

I tried to compile the simplest libfuse example "hello.c" and link it with OSXFUSE. After mounting it, I cannot see the file system in Finder. However, I can see other file systems like YoutubeFS and in Finder. The implementation of "hello.c" is quite simple (I made some changes to let it work with OSXFUSE):

#include <osxfuse/fuse.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>

static const char *hello_str = "Hello World!\n";
static const char *hello_path = "/hello";

static int hello_getattr(const char *path, struct stat *stbuf)
{
    printf("getattr, path: %s\n", path);
	int res = 0;

	if (strcmp(path, hello_path) == 0) {
		stbuf->st_mode = S_IFREG | 0444;
		stbuf->st_nlink = 1;
		stbuf->st_size = strlen(hello_str);
	} else
		res = -ENOENT;

	return res;
}

static int hello_readdir(const char *path, void *buf, fuse_fill_dir_t filler,
			 off_t offset, struct fuse_file_info *fi)
{
	(void) offset;
	(void) fi;
    printf("readdir, path: %s\n", path);

	if (strcmp(path, "/") != 0)
		return -ENOENT;

	filler(buf, ".", NULL, 0);
	filler(buf, "..", NULL, 0);
	filler(buf, hello_path + 1, NULL, 0);

	return 0;
}

static int hello_open(const char *path, struct fuse_file_info *fi)
{
	if (strcmp(path, hello_path) != 0)
		return -ENOENT;

	if ((fi->flags & 3) != O_RDONLY)
		return -EACCES;

	return 0;
}

static int hello_read(const char *path, char *buf, size_t size, off_t offset,
		      struct fuse_file_info *fi)
{
	size_t len;
	(void) fi;
	if(strcmp(path, hello_path) != 0)
		return -ENOENT;

	len = strlen(hello_str);
	if (offset < len) {
		if (offset + size > len)
			size = len - offset;
		memcpy(buf, hello_str + offset, size);
	} else
		size = 0;

	return size;
}

static void *hello_init(struct fuse_conn_info *conn)
{
    printf("init\n");
    return NULL;
}

static struct fuse_operations hello_oper = {
	.getattr	= hello_getattr,
	.readdir	= hello_readdir,
	.open		= hello_open,
	.read		= hello_read,
    .init       = hello_init,
};

int main(int argc, char *argv[])
{
	return fuse_main(argc, argv, &hello_oper, NULL);
}

I build the executable with command

clang -D_FILE_OFFSET_BITS=64 hello.c -losxfuse -o hello

How to make this simple toy show up in Finder?

Sam Moffatt

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Jul 10, 2016, 7:34:17 PM7/10/16

to osxfus...@googlegroups.com

Finder can be picky about what it thinks is legit or not. In the past I’ve had plenty of issues with Finder deciding to not show anything because the data it got back from my file system was inconsistent.

What I’d personally do is run your file system in debug mode and see exactly what FS operations are being called and what is being returned. It’s possible that there is a call to your filesystem for some folder metadata that is being returned in such a way that Finder is assuming it doesn’t exist.

Also keep in mind that Mac OS X’s VFS layer is slightly different to the Linux VFS layer and there are different behaviours that aren’t 100% compatible. IMHO OSXFUSE does a good job of isolating a lot of that but there are various system calls that outright behave differently on the two OS’s that makes development a pain.

I copied your code and tried to compile as is with the latest non developer version of OSXFUSE however I got the standard FUSE version error. I modified it slightly to fix that (adding a def for FUSE_USE_VERSION ahead of the fuse.h import) and it compiled.

Running in debug mode there are a lot of failed calls:

pancake:osxfuse_hello pasamio$ ./hello -d -s mount

unique: 0, opcode: INIT (26), nodeid: 0, insize: 56

INIT: 7.8

flags=0x00000000

max_readahead=0x00100000

init

INIT: 7.8

flags=0x00000000

max_readahead=0x00100000

max_write=0x01000000

unique: 0, error: 0 (Undefined error: 0), outsize: 40

unique: 0, opcode: STATFS (17), nodeid: 1, insize: 40