Re: [PATCH] AFS: Fix file locking

Nick Piggin
2007-07-20T02:03:34Z

Andrew Morton wrote:
> On Tue, 17 Jul 2007 13:47:32 +0100
> David Howells <dhowells@redhat.com> wrote:
>
>
>>+ if (type == AFS_LOCK_READ &&
>>+ vnode->flags & (1 << AFS_VNODE_READLOCKED)) {
>
>
> Here we use
>
> vnode->flags & (1 << foo)
>
>
>>+ set_bit(AFS_VNODE_LOCKING, &vnode->flags);
>
>
> and elsewhere we use set_bit(foo, &vnode->flags) and clear_bit()
>
> This is a bit strange. Does the open-coded bit-test have any performance
> benefit on any architecture? Not on x86 at least, afaik.

It uses locked operations on x86, but you can use __set_bit instead
(which should always be at least as efficient as the C version).

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SUSE Labs, Novell Inc.