scan directory content in kernel-level code

[christophe barbe]

I'm trying to scan the content of the /dev directory in a init_module function.
I've not found example in the kernel source. So I try to reproduce the work of the 
system call.
I open the directory, check if the readdir pointer is not null in the f_op structure 
and then use it with my filldir function.
Because I don't need to stock names, I use filename directly in the filldir callback.
So in the filldir function, I check if the name match a simple regexp and if yes, I 
open the file and store the filp pointer.

First I don't understand why I need to call several times readdir in order to scan the 
directory (I imagine each times I obtain the content of one buffer). I check the 
number of callback call to stop calling readdir. It works but it seems strange.

Second problem, Sometimes the modprobe dead-locks in my filldir function. And I've 
found that it never arrives if i do a "ls /dev" before modprobe. Moreover if I don't 
take the directory inode semaphore, the problem never arrives. 
What's wrong ?

Christophe ...


struct my_dentry {
        char fullname[5];
        char name[MAX_DEVNAME_SIZE+1];
        int count;
};

int my_filldir(void * __buf, const char * name, int namlen, off_t offset, ino_t ino, 
unsigned unused)
{
        struct my_dentry * buf = (struct my_dentry *)__buf;

        if (namlen>MAX_DEVNAME_SIZE) namlen=MAX_DEVNAME_SIZE;

        memcpy((char *)buf->name, name, namlen);
        buf->name[namlen]='\0';
        check_device(buf->fullname);  // here I open the file if the string match 
criteria
        buf->count++;
        return 0;
}

void scan_device_directory(void)
{
        struct file * filp;
        struct inode * d_inode;
        struct my_dentry dir_entry={"/dev/",};
        int rc;

        filp = filp_open("/dev", O_RDONLY|O_SYNC, 0600);
        if ((rc=IS_ERR(filp))>0)  {
                printk("bad filp : %d\n", rc);
                return;
        }

        d_inode = filp->f_dentry->d_inode;
        if (!d_inode) {
                printk("NULL inode\n");
                goto out_close_dir;
        }

        if (! S_ISDIR(d_inode->i_mode)) {
                printk("/dev is not a directory (?)\n");
                goto out_close_dir;
        }

        if (filp->f_op->readdir == NULL) {
                printk("can't find readidir f_ops\n");
                goto out_close_dir;
        }

        v_printk("/dev : inode=%ld\n", d_inode->i_ino);

        down(&d_inode->i_sem);

        do {
                dir_entry.count=0;
                rc=filp->f_op->readdir(filp, (void *)&dir_entry, my_filldir);
        } while (dir_entry.count>0);

        up(&d_inode->i_sem);

out_close_dir:
        fput(filp);
}

-- 
Christophe Barbé
Software Engineer
Lineo High Availability Group
42-46, rue Médéric
92110 Clichy - France
phone (33).1.41.40.02.12
fax (33).1.41.40.02.01
www.lineo.com
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/