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Subject[PATCH v3 4/6] mm/slub: distinguish and print stack traces in debugfs files
Date
From: Oliver Glitta <glittao@gmail.com>

Aggregate objects in slub cache by unique stack trace in addition to
caller address when producing contents of debugfs files alloc_traces and
free_traces in debugfs. Also add the stack traces to the debugfs output.
This makes it much more useful to e.g. debug memory leaks.

Signed-off-by: Oliver Glitta <glittao@gmail.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-and-tested-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
---
mm/slub.c | 28 ++++++++++++++++++++++++++--
1 file changed, 26 insertions(+), 2 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 98c1450c23f0..f2e550e1adf0 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -5064,6 +5064,7 @@ EXPORT_SYMBOL(validate_slab_cache);
*/

struct location {
+ depot_stack_handle_t handle;
unsigned long count;
unsigned long addr;
long long sum_time;
@@ -5116,9 +5117,13 @@ static int add_location(struct loc_track *t, struct kmem_cache *s,
{
long start, end, pos;
struct location *l;
- unsigned long caddr;
+ unsigned long caddr, chandle;
unsigned long age = jiffies - track->when;
+ depot_stack_handle_t handle = 0;

+#ifdef CONFIG_STACKDEPOT
+ handle = READ_ONCE(track->handle);
+#endif
start = -1;
end = t->count;

@@ -5133,7 +5138,8 @@ static int add_location(struct loc_track *t, struct kmem_cache *s,
break;

caddr = t->loc[pos].addr;
- if (track->addr == caddr) {
+ chandle = t->loc[pos].handle;
+ if ((track->addr == caddr) && (handle == chandle)) {

l = &t->loc[pos];
l->count++;
@@ -5158,6 +5164,8 @@ static int add_location(struct loc_track *t, struct kmem_cache *s,

if (track->addr < caddr)
end = pos;
+ else if (track->addr == caddr && handle < chandle)
+ end = pos;
else
start = pos;
}
@@ -5180,6 +5188,7 @@ static int add_location(struct loc_track *t, struct kmem_cache *s,
l->max_time = age;
l->min_pid = track->pid;
l->max_pid = track->pid;
+ l->handle = handle;
cpumask_clear(to_cpumask(l->cpus));
cpumask_set_cpu(track->cpu, to_cpumask(l->cpus));
nodes_clear(l->nodes);
@@ -6089,6 +6098,21 @@ static int slab_debugfs_show(struct seq_file *seq, void *v)
seq_printf(seq, " nodes=%*pbl",
nodemask_pr_args(&l->nodes));

+#ifdef CONFIG_STACKDEPOT
+ {
+ depot_stack_handle_t handle;
+ unsigned long *entries;
+ unsigned int nr_entries, j;
+
+ handle = READ_ONCE(l->handle);
+ if (handle) {
+ nr_entries = stack_depot_fetch(handle, &entries);
+ seq_puts(seq, "\n");
+ for (j = 0; j < nr_entries; j++)
+ seq_printf(seq, " %pS\n", (void *)entries[j]);
+ }
+ }
+#endif
seq_puts(seq, "\n");
}

--
2.35.1
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