Re: [PATCH 5 2/4] Return 32/64-bit dir name hash according to usage type

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Tue, Mar 06, 2012 at 01:40:05AM +0100, Bernd Schubert wrote:
> 
> Yeah, you are right, we also should check for 64-bit EOF. But
> wouldn't be something like this be better?
> 
> 	/* check for hash collision */
> 	if(is_32bit_api() ) {
> 		if (hash == (EXT4_HTREE_EOF_32BIT<<  1))
> 			hash = (EXT4_HTREE_EOF_32BIT - 1)<<  1;
> 	} else {
> 		if (hash == (EXT4_HTREE_EOF_64BIT<<  1))
> 			hash = (EXT4_HTREE_EOF_64BIT - 1)<<  1;
> 	}

Actually, neither change is needed, now that I look at things more
closely.  hash is a __u32, so it could never been
EXT4_HTREE_EOF_64BIT.  But given that we won't let major hash become
larger than 0xfffffffc, that means the largest possible position value
is 0x7ffffffeffffffff.  So using an EOF value of 0x0x7fffffffffffffff
will work fine.

The bigger problem that I found when I looked more closely at the
patch is that the patch uses f_flags in places where f_mode needs to
be used:

static inline loff_t hash2pos(struct file *filp, __u32 major, __u32 minor)
{
	if ((filp->f_flags & FMODE_32BITHASH) ||
                   ^^^^^^^
	    (!(filp->f_flags & FMODE_64BITHASH) && is_32bit_api()))
                     ^^^^^^^
		return major >> 1;
	else
		return ((__u64)(major >> 1) << 32) | (__u64)minor;
}

static inline __u32 pos2maj_hash(struct file *filp, loff_t pos)
{
	if ((filp->f_flags & FMODE_32BITHASH) ||
                   ^^^^^^
	    (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
                     ^^^^^^
		return (pos << 1) & 0xffffffff;
	else
		return ((pos >> 32) << 1) & 0xffffffff;
}

Which makes me wonder how much this has been tested?

      	       	      	       	    	     - Ted
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html


[Index of Archives]     [Reiser Filesystem Development]     [Ceph FS]     [Kernel Newbies]     [Security]     [Netfilter]     [Bugtraq]     [Linux FS]     [Yosemite National Park]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Samba]     [Device Mapper]     [Linux Media]

  Powered by Linux