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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>The attached patch corrects a bug where
group permission checking was failing for a group with 221 members. The patch
changes the logic for group permission checking up a bit. Rather than get the
user list from the group, this patch gets the groups that the user is a member
of. I’m taking the assumption that groups probably have a large number of
members, but users usually have less number of groups. This also seemed to help
out a bit on the required memory allocations. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><b><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>
pvfs2-developers-bounces@beowulf-underground.org
[mailto:pvfs2-developers-bounces@beowulf-underground.org] <b><span
style='font-weight:bold'>On Behalf Of </span></b>David Metheny<br>
<b><span style='font-weight:bold'>Sent:</span></b> Thursday, March 12, 2009
11:32 AM<br>
<b><span style='font-weight:bold'>To:</span></b>
pvfs2-developers@beowulf-underground.org<br>
<b><span style='font-weight:bold'>Subject:</span></b> [Pvfs2-developers] PVFS2
group permission checking failing forgroups with large number of members</span></font><o:p></o:p></p>
</div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>I’ve run into an issue where permissions are failing
during group permission checking (PINT_check_group). <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>The example case is where userA is a member of groupA.
groupA has 221 member users. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Courier New"><span style='font-size:10.0pt;
font-family:"Courier New"'>drwxrwx--- 1 userB
groupA 4096 Mar 11 15:35 subdir<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>The PINT_check_mode uses the sysconf call to determine the
size of the buffer to use for lookups on groups and users. In this case, the
users/groups are stored in LDAP. The call here is check_group_gr_buffer_size =
sysconf(_SC_GETGR_R_SIZE_MAX). As a default, if we can’t make the sysconf
call, it is being set to 1024 bytes. For RHEL4 systems in our environments, the
sysconf is also returning 1024.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>In the above situation, 1024 isn’t a large enough
buffer to allocate all of the member usernames associated with the group, and
the getgrgid_r function call returns an error.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>As easy enough change would be to increase the buffer size
used. Another idea would be to change the call up a bit to get the groups that
the user is part of, and compare those groups against the group for the file.
Are there any thoughts on which approach to implement? I’m not sure which
would be faster in general, but in the environments I’m seeing, users are
in less groups, than groups have members. If we change the logic on group
checking, I’m assuming we would also want to implement a larger buffer
size for both the group and user lookups. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
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font-family:Arial'><o:p> </o:p></span></font></p>
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font-family:Arial'><o:p> </o:p></span></font></p>
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font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
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size=2 color="#666666" face=Arial><span style='font-size:10.0pt;font-family:
Arial;color:#666666'><o:p> </o:p></span></font></p>
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12.0pt'><o:p> </o:p></span></font></p>
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