[Tux3] [RFC] Refactor create_entry and find_entry to work with xattrs

Daniel Phillips phillips at phunq.net
Fri Dec 12 02:21:21 PST 2008

On Friday 12 December 2008 01:56, OGAWA Hirofumi wrote:
> ...Just FYI for people, probably you know though,
> inode->i_size has race on 32bit arch. It is 64bit value, so,
> 	*size += blocksize;
> means something like the following. E.g.
> 	load 0x0(size), %reg1
> 	load 0x4(size), %reg2
>         add blocksize, %reg1
>         add-carry %reg2
> 	store %reg1, 0x0(size)
>         			<---- (W)
> 	store %reg2, 0x4(size)
> So, block I/O library like block_write_full_page() can read the size at
> (W) point. The result may be bogus size.
> We have to fix this later, maybe change with phtree. (don't read i_size
> without lock, or use i_size_read()/i_size_write())

Ah, I thought about that when you mentioned it earlier and forgot to
take care of it in my patch.  Something like this:

loff_t tux_create_entry(struct inode *dir, const char *name, int len, inum_t inum, unsigned mode)
	loff_t size = i_size_read(dir);
	int err = _tux_create_entry(dir, name, len, inum, mode, &size);
	i_size_write(dir, size);
	return err;



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