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[RFC 4/5] Page allocation fault injection script
- From: Anup C Shan <anupcshan at gmail dot com>
- To: systemtap at sources dot redhat dot com
- Cc: kghoshnitk at gmail dot com, akinobu dot mita at gmail dot com, k-tanaka at ce dot jp dot nec dot com
- Date: Fri, 11 Jul 2008 15:39:25 +0530
- Subject: [RFC 4/5] Page allocation fault injection script
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#!/usr/local/bin/stap
/*
* This script is used to fail __alloc_pages() function in mm/page_alloc.c
*/
probe begin(0)
{
fij_load_param(20000,0,100,0,0,1,1000);
fij_add_option("min_order",0,"Minimum order(base 2) of the allocation")
fij_add_gfp_wait_param()
fij_add_gfp_highmem_param()
}
global min_order
probe begin(2000)
{
min_order = fij_params["min_order"]
}
function should_fail_alloc(order:long,flags:long)
{
if (order < min_order) {
fij_logger(100,sprintf("Skipping on order %d",order))
return 0
} else
fij_logger(100,sprintf("Continuing on order %d",order))
if (fij_should_fail_gfp_wait(flags) == 0)
return 0
if (fij_should_fail_gfp_highmem(flags) == 0)
return 0
if (fij_should_fail() == 0)
return 0
return 1
}
global zones_save,under_fail
/*
* zones_save : Temporary variable to save zone information that will be
* assigned fake value to induce fault.
* under_fail : Flag to denote whether system is under fault injected condition.
* Both these variables are 'per-cpu' variables to prevent race conditions.
*/
function nullify(zptr:long,cpu:long)
%{
struct zones **z = (struct zones **)(THIS->zptr);
THIS->__retvalue = (long)*z;
*z = NULL;
%}
/*
* Method of fault injection :
* The function __alloc_pages() is failed by using an if condition on
* variable z (=zonelist->zones).
* To fail, the value of *(zonelist->zones) is saved in zones_save and
* set to NULL to cause the function to return NULL value.
* Once the fault is injected, the value of zonelist->zones is restored.
*/
probe kernel.function("__alloc_pages@mm/page_alloc.c")
{
if (should_fail_alloc($order,$gfp_mask) == 0)
next
zones_save[cpu()] = nullify($zonelist->zones,cpu())
under_fail[cpu()] = 1
fij_done_fail()
}
function restore(zones:long,zones_save:long)
%{
struct zones **z = (struct zones **)(THIS->zones);
*z = (struct zones *)THIS->zones_save;
%}
probe kernel.function("__alloc_pages@mm/page_alloc.c").return
{
if (under_fail[cpu()]) {
restore($zonelist->zones,zones_save[cpu()])
under_fail[cpu()] = 0
}
}