[PATCH v3 1/2] slub: Enable backtrace for create/delete points.

From: Ben Greear <greearb@candelatech.com>

This patch attempts to grab a backtrace for the creation
and deletion points of the slub object. When a fault is
detected, we can then get a better idea of where the item
was deleted.

Signed-off-by: Ben Greear <greearb@candelatech.com>


v3: Don't rename addr to caddr.
Move 'int i' into #ifdef block to ensure there is no
warning when #ifdef'd code is not compiled.

:100644 100644 35f351f... c52fa60... M mm/slub.c
mm/slub.c | 32 ++++++++++++++++++++++++++++++++
1 files changed, 32 insertions(+), 0 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 35f351f..c52fa60 100644
a/mm/slub.c
+++ b/mm/slub.c
@@ -191,8 +191,12 @@ static LIST_HEAD(slab_caches);
/*
* Tracking user of a slab.
*/
+#define TRACK_ADDRS_COUNT 16
struct track {
unsigned long addr; /* Called from address */
+#ifdef CONFIG_STACKTRACE
+ unsigned long addrs[TRACK_ADDRS_COUNT]; /* Called from address */
+#endif
int cpu; /* Was running on cpu */
int pid; /* Pid context */
unsigned long when; /* When did the operation occur */
@@ -420,6 +424,24 @@ static void set_track(struct kmem_cache *s, void *object,
struct track *p = get_track(s, object, alloc);

if (addr) {
+#ifdef CONFIG_STACKTRACE
+ struct stack_trace trace;
+ int i;
+
+ trace.nr_entries = 0;
+ trace.max_entries = TRACK_ADDRS_COUNT;
+ trace.entries = p->addrs;
+ trace.skip = 3;
+ save_stack_trace(&trace);
+
+ /* See rant in lockdep.c */
+ if (trace.nr_entries != 0 &&
+ trace.entries[trace.nr_entries - 1] == ULONG_MAX)
+ trace.nr_entries--;
+
+ for (i = trace.nr_entries; i < TRACK_ADDRS_COUNT; i++)
+ p->addrs[i] = 0;
+#endif
p->addr = addr;
p->cpu = smp_processor_id();
p->pid = current->pid;
@@ -444,6 +466,16 @@ static void print_track(const char *s, struct track *t)

printk(KERN_ERR "INFO: %s in %pS age=%lu cpu=%u pid=%d",
s, (void *)t->addr, jiffies - t->when, t->cpu, t->pid);
+#ifdef CONFIG_STACKTRACE
+ {
+ int i;
+ for (i = 0; i < TRACK_ADDRS_COUNT; i++)
+ if (t->addrs[i])
+ printk(KERN_ERR "\t%pS", (void *)t->addrs[i]);
+ else
+ break;
+ }
+#endif
}

static void print_tracking(struct kmem_cache *s, void *object)
1.7.3.4

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