Re: silent semantic changes with reiser4

[Linus Torvalds]

On Sat, 28 Aug 2004 viro@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx wrote:
> 
> What would your openat() produce?  Normal struct file?  Then what's going
> to be its vfsmount/dentry and what will they be attached to?

Normal file descriptor, exactly like "open()".

And it's going to have all the same vfsmount/dentry thing it would have if 
you looked it up the whole way. I don't understand your question..

Ignore the O_XATTR thing for a while, and assume it's just a convenient
combination of "fchdir + open" (plus "fchdir back" of course, but that's 
beside the point - openat() doesn't ever really change cwd).

Going back to O_XATTR: that would end up doing the "special vfsmount"  
magic at the beginning of the lookup. If the dentry you started with
wasn't marked D_HYBRID, it would just return -ENOTDIR.

So we could do openat() _without_ any of the lookup_mnt() etc special 
cases. This interface is independent of whether we want to expose the 
attributes through a normal lookup - we can do either, both, or neither as 
we choose.

The nice thing about "openat()" is
 - people can definitely find uses for it even without attributes. 
 - it's "portable". Well, at least somebody else does the same thing, 
   which is nice for user-space developers. You don't use a Linux-only 
   interface, you use a Linux/Solaris one, which makes a lot of people a 
   lot more happy.

Remember, portability has always been very important to Linux, and
Linux-only features while nice are certainly not as nice as features you
can also find in other places.

NIH is a disease.

		Linus
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/