Reading from file in module fails

[Libor Vanek <libor@conet.cz>]

Hi,
I'm writing module which needs to read from file. I've got this simple sample code:

char buffer[4096];
ssize_t read;
file *f;
f = filp_open("/some/file",O_RDONLY | O_LARGEFILE,0);
f->f_pos = 0;
read = vfs_read(f,(char __user *) buffer,4096,&f->f_pos);

but here read value is "-14" (-EINVAL?) Does anybody has idea what's wrong? 

It seems that file is opened OK (I've tested:
if (f->f_op->read) {
	read = f->f_op->read(file, buf, count, pos);
}
and result was the same - so I assume that file is opened OK and structure "file f" is filled correctly.


I need to copy files (yes - I know that kernel shouldn't do this but I REALLY need) and there is nothing like "sys_copy" and "sys_sendfile" is not exported (which seems strange to me but there is nothing like EXPORT_SYMBOL(sys_sendfile) in fs/read_write.c


Thanks,
Libor Vanek