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SubjectRe: [PATCH 5/5] Swap Migration V5: sys_migrate_pages interface
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On Tue, 1 Nov 2005, Andrew Morton wrote:

> Christoph Lameter <clameter@sgi.com> wrote:
>>
>> ...
>> Changes V3->V4:
>> - Add Ray's permissions check based on check_kill_permission().
>>
>> ...
>> + /*
>> + * Permissions check like for signals.
>> + * See check_kill_permission()
>> + */
>> + if ((current->euid ^ task->suid) && (current->euid ^ task->uid) &&
>> + (current->uid ^ task->suid) && (current->uid ^ task->uid) &&
>> + !capable(CAP_SYS_ADMIN)) {
>> + err = -EPERM;
>> + goto out;
>> + }
>
> Obscure. Can you please explain the thinking behind putting this check in
> here? Preferably via a comment...

Also XOR is not a good substitute for a compare. Except in some
strange corner cases, the code will always take more CPU cycles
because XOR modifies oprands while compares don't need to.


Cheers,
Dick Johnson
Penguin : Linux version 2.6.13.4 on an i686 machine (5589.55 BogoMips).
Warning : 98.36% of all statistics are fiction.
.

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