mm: make should_failslab always available for fault injection
should_failslab() is a convenient function to hook into for directed
error injection into kmalloc(). However, it is only available if a
config flag is set.
The following BCC script, for example, fails kmalloc() calls after a
btrfs umount:
from bcc import BPF
prog = r"""
BPF_HASH(flag);
#include <linux/mm.h>
int kprobe__btrfs_close_devices(void *ctx) {
u64 key = 1;
flag.update(&key, &key);
return 0;
}
int kprobe__should_failslab(struct pt_regs *ctx) {
u64 key = 1;
u64 *res;
res = flag.lookup(&key);
if (res != 0) {
bpf_override_return(ctx, -ENOMEM);
}
return 0;
}
"""
b = BPF(text=prog)
while 1:
b.kprobe_poll()
This patch refactors the should_failslab implementation so that the
function is always available for error injection, independent of flags.
This change would be similar in nature to commit f5490d3ec921 ("block:
Add should_fail_bio() for bpf error injection").
Link: http://lkml.kernel.org/r/20180222020320.6944-1-hmclauchlan@fb.com
Signed-off-by: Howard McLauchlan <hmclauchlan@fb.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Josef Bacik <jbacik@fb.com>
Cc: Johannes Weiner <jweiner@fb.com>
Cc: Alexei Starovoitov <ast@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 2e682a4..98dcdc3 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -1516,3 +1516,11 @@
EXPORT_TRACEPOINT_SYMBOL(kmem_cache_alloc_node);
EXPORT_TRACEPOINT_SYMBOL(kfree);
EXPORT_TRACEPOINT_SYMBOL(kmem_cache_free);
+
+int should_failslab(struct kmem_cache *s, gfp_t gfpflags)
+{
+ if (__should_failslab(s, gfpflags))
+ return -ENOMEM;
+ return 0;
+}
+ALLOW_ERROR_INJECTION(should_failslab, ERRNO);