Re: [BK PATCH 1/2] Remove NGROUPS hardlimit (resend w/o qsort)

[Tim Hockin <thockin@sun.com>]

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