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Date: Thu, 14 Nov 2002 17:24:16 -0800
From: Tim Hockin <thockin@sun.com>
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To: Andrew Morton <akpm@digeo.com>,
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Subject: Re: [BK PATCH 1/2] Remove NGROUPS hardlimit (resend w/o qsort)
References: <mailman.1037316781.6599.linux-kernel2news@redhat.com> <200211150006.gAF06JF01621@devserv.devel.redhat.com> <3DD43C65.80103@sun.com> <20021114193156.A2801@devserv.devel.redhat.com> <3DD443EC.2080504@sun.com> <3DD44742.2DFE4407@digeo.com>
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Andrew Morton wrote:

> What are you actually using the search for?
> 
>>From a quick look, it seems that it's purely to answer
> the question "is this process a member of group X?".  Is
> that correct?
> 
> If so, test_bit() would work nicely.

This could work if we find the max gid, allocate an array of 
max_gid/CHAR_BITS + 1 bytes then test_bit, but given the non-contiguity 
(is that a word) of group memberships, we'll waste a lot of space on 
holes. Now, it could be argued that 10,000 groups are PROBABLY local 
enough.  Getting the groups back out will be nasty nastiness, though.

perhaps:

if (gidsetsize < (2 * EXEC_PAGESIZE)/sizeof(gid_t)) { /* or something */
	/* use kmalloc() */
else
	/* use vmalloc() */

thoughts?

-- 
Tim Hockin
Systems Software Engineer
Sun Microsystems, Linux Kernel Engineering
thockin@sun.com

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