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de1ba09b AM |
1 | Fault injection capabilities infrastructure |
2 | =========================================== | |
3 | ||
4 | See also drivers/md/faulty.c and "every_nth" module option for scsi_debug. | |
5 | ||
6 | ||
7 | Available fault injection capabilities | |
8 | -------------------------------------- | |
9 | ||
10 | o failslab | |
11 | ||
12 | injects slab allocation failures. (kmalloc(), kmem_cache_alloc(), ...) | |
13 | ||
14 | o fail_page_alloc | |
15 | ||
16 | injects page allocation failures. (alloc_pages(), get_free_pages(), ...) | |
17 | ||
18 | o fail_make_request | |
19 | ||
20 | injects disk IO errors on permitted devices by | |
21 | /sys/block/<device>/make-it-fail or | |
22 | /sys/block/<device>/<partition>/make-it-fail. (generic_make_request()) | |
23 | ||
24 | Configure fault-injection capabilities behavior | |
25 | ----------------------------------------------- | |
26 | ||
27 | o debugfs entries | |
28 | ||
29 | fault-inject-debugfs kernel module provides some debugfs entries for runtime | |
30 | configuration of fault-injection capabilities. | |
31 | ||
32 | - /debug/*/probability: | |
33 | ||
34 | likelihood of failure injection, in percent. | |
35 | Format: <percent> | |
36 | ||
37 | Note that one-failure-per-handred is a very high error rate | |
38 | for some testcases. Please set probably=100 and configure | |
39 | /debug/*/interval for such testcases. | |
40 | ||
41 | - /debug/*/interval: | |
42 | ||
43 | specifies the interval between failures, for calls to | |
44 | should_fail() that pass all the other tests. | |
45 | ||
46 | Note that if you enable this, by setting interval>1, you will | |
47 | probably want to set probability=100. | |
48 | ||
49 | - /debug/*/times: | |
50 | ||
51 | specifies how many times failures may happen at most. | |
52 | A value of -1 means "no limit". | |
53 | ||
54 | - /debug/*/space: | |
55 | ||
56 | specifies an initial resource "budget", decremented by "size" | |
57 | on each call to should_fail(,size). Failure injection is | |
58 | suppressed until "space" reaches zero. | |
59 | ||
60 | - /debug/*/verbose | |
61 | ||
62 | Format: { 0 | 1 | 2 } | |
63 | specifies the verbosity of the messages when failure is injected. | |
64 | We default to 0 (no extra messages), setting it to '1' will | |
65 | print only to tell failure happened, '2' will print call trace too - | |
66 | it is useful to debug the problems revealed by fault injection | |
67 | capabilities. | |
68 | ||
69 | - /debug/*/task-filter: | |
70 | ||
71 | Format: { 0 | 1 } | |
72 | A value of '0' disables filtering by process (default). | |
73 | Any positive value limits failures to only processes indicated by | |
74 | /proc/<pid>/make-it-fail==1. | |
75 | ||
76 | - /debug/*/address-start: | |
77 | - /debug/*/address-end: | |
78 | ||
79 | specifies the range of virtual addresses tested during | |
80 | stacktrace walking. Failure is injected only if some caller | |
81 | in the walked stacktrace lies within this range. | |
82 | Default is [0,ULONG_MAX) (whole of virtual address space). | |
83 | ||
84 | - /debug/*/stacktrace-depth: | |
85 | ||
86 | specifies the maximum stacktrace depth walked during search | |
87 | for a caller within [address-start,address-end). | |
88 | ||
89 | - /debug/failslab/ignore-gfp-highmem: | |
90 | - /debug/fail_page_alloc/ignore-gfp-highmem: | |
91 | ||
92 | Format: { 0 | 1 } | |
93 | default is 0, setting it to '1' won't inject failures into | |
94 | highmem/user allocations. | |
95 | ||
96 | - /debug/failslab/ignore-gfp-wait: | |
97 | - /debug/fail_page_alloc/ignore-gfp-wait: | |
98 | ||
99 | Format: { 0 | 1 } | |
100 | default is 0, setting it to '1' will inject failures | |
101 | only into non-sleep allocations (GFP_ATOMIC allocations). | |
102 | ||
103 | o Boot option | |
104 | ||
105 | In order to inject faults while debugfs is not available (early boot time), | |
106 | use the boot option: | |
107 | ||
108 | failslab= | |
109 | fail_page_alloc= | |
110 | fail_make_request=<interval>,<probability>,<space>,<times> | |
111 | ||
112 | How to add new fault injection capability | |
113 | ----------------------------------------- | |
114 | ||
115 | o #include <linux/fault-inject.h> | |
116 | ||
117 | o define the fault attributes | |
118 | ||
119 | DECLARE_FAULT_INJECTION(name); | |
120 | ||
121 | Please see the definition of struct fault_attr in fault-inject.h | |
122 | for details. | |
123 | ||
124 | o provide the way to configure fault attributes | |
125 | ||
126 | - boot option | |
127 | ||
128 | If you need to enable the fault injection capability from boot time, you can | |
129 | provide boot option to configure it. There is a helper function for it. | |
130 | ||
131 | setup_fault_attr(attr, str); | |
132 | ||
133 | - debugfs entries | |
134 | ||
135 | failslab, fail_page_alloc, and fail_make_request use this way. | |
136 | There is a helper function for it. | |
137 | ||
138 | init_fault_attr_entries(entries, attr, name); | |
139 | void cleanup_fault_attr_entries(entries); | |
140 | ||
141 | - module parameters | |
142 | ||
143 | If the scope of the fault injection capability is limited to a | |
144 | single kernel module, it is better to provide module parameters to | |
145 | configure the fault attributes. | |
146 | ||
147 | o add a hook to insert failures | |
148 | ||
149 | should_fail() returns 1 when failures should happen. | |
150 | ||
151 | should_fail(attr,size); | |
152 | ||
153 | Application Examples | |
154 | -------------------- | |
155 | ||
156 | o inject slab allocation failures into module init/cleanup code | |
157 | ||
158 | ------------------------------------------------------------------------------ | |
159 | #!/bin/bash | |
160 | ||
161 | FAILCMD=Documentation/fault-injection/failcmd.sh | |
162 | BLACKLIST="root_plug evbug" | |
163 | ||
164 | FAILNAME=failslab | |
165 | echo Y > /debug/$FAILNAME/task-filter | |
166 | echo 10 > /debug/$FAILNAME/probability | |
167 | echo 100 > /debug/$FAILNAME/interval | |
168 | echo -1 > /debug/$FAILNAME/times | |
169 | echo 2 > /debug/$FAILNAME/verbose | |
170 | echo 1 > /debug/$FAILNAME/ignore-gfp-highmem | |
171 | echo 1 > /debug/$FAILNAME/ignore-gfp-wait | |
172 | ||
173 | blacklist() | |
174 | { | |
175 | echo $BLACKLIST | grep $1 > /dev/null 2>&1 | |
176 | } | |
177 | ||
178 | oops() | |
179 | { | |
180 | dmesg | grep BUG > /dev/null 2>&1 | |
181 | } | |
182 | ||
183 | find /lib/modules/`uname -r` -name '*.ko' -exec basename {} .ko \; | | |
184 | while read i | |
185 | do | |
186 | oops && exit 1 | |
187 | ||
188 | if ! blacklist $i | |
189 | then | |
190 | echo inserting $i... | |
191 | bash $FAILCMD modprobe $i | |
192 | fi | |
193 | done | |
194 | ||
195 | lsmod | awk '{ if ($3 == 0) { print $1 } }' | | |
196 | while read i | |
197 | do | |
198 | oops && exit 1 | |
199 | ||
200 | if ! blacklist $i | |
201 | then | |
202 | echo removing $i... | |
203 | bash $FAILCMD modprobe -r $i | |
204 | fi | |
205 | done | |
206 | ||
207 | ------------------------------------------------------------------------------ | |
208 | ||
209 | o inject slab allocation failures only for a specific module | |
210 | ||
211 | ------------------------------------------------------------------------------ | |
212 | #!/bin/bash | |
213 | ||
214 | FAILMOD=Documentation/fault-injection/failmodule.sh | |
215 | ||
216 | echo injecting errors into the module $1... | |
217 | ||
218 | modprobe $1 | |
219 | bash $FAILMOD failslab $1 10 | |
220 | echo 25 > /debug/failslab/probability | |
221 | ||
222 | ------------------------------------------------------------------------------ | |
223 |