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-rw-r--r--lib/ref_tracker.c275
1 files changed, 275 insertions, 0 deletions
diff --git a/lib/ref_tracker.c b/lib/ref_tracker.c
new file mode 100644
index 0000000000..cf5609b1ca
--- /dev/null
+++ b/lib/ref_tracker.c
@@ -0,0 +1,275 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#define pr_fmt(fmt) "ref_tracker: " fmt
+
+#include <linux/export.h>
+#include <linux/list_sort.h>
+#include <linux/ref_tracker.h>
+#include <linux/slab.h>
+#include <linux/stacktrace.h>
+#include <linux/stackdepot.h>
+
+#define REF_TRACKER_STACK_ENTRIES 16
+#define STACK_BUF_SIZE 1024
+
+struct ref_tracker {
+ struct list_head head; /* anchor into dir->list or dir->quarantine */
+ bool dead;
+ depot_stack_handle_t alloc_stack_handle;
+ depot_stack_handle_t free_stack_handle;
+};
+
+struct ref_tracker_dir_stats {
+ int total;
+ int count;
+ struct {
+ depot_stack_handle_t stack_handle;
+ unsigned int count;
+ } stacks[];
+};
+
+static struct ref_tracker_dir_stats *
+ref_tracker_get_stats(struct ref_tracker_dir *dir, unsigned int limit)
+{
+ struct ref_tracker_dir_stats *stats;
+ struct ref_tracker *tracker;
+
+ stats = kmalloc(struct_size(stats, stacks, limit),
+ GFP_NOWAIT | __GFP_NOWARN);
+ if (!stats)
+ return ERR_PTR(-ENOMEM);
+ stats->total = 0;
+ stats->count = 0;
+
+ list_for_each_entry(tracker, &dir->list, head) {
+ depot_stack_handle_t stack = tracker->alloc_stack_handle;
+ int i;
+
+ ++stats->total;
+ for (i = 0; i < stats->count; ++i)
+ if (stats->stacks[i].stack_handle == stack)
+ break;
+ if (i >= limit)
+ continue;
+ if (i >= stats->count) {
+ stats->stacks[i].stack_handle = stack;
+ stats->stacks[i].count = 0;
+ ++stats->count;
+ }
+ ++stats->stacks[i].count;
+ }
+
+ return stats;
+}
+
+struct ostream {
+ char *buf;
+ int size, used;
+};
+
+#define pr_ostream(stream, fmt, args...) \
+({ \
+ struct ostream *_s = (stream); \
+\
+ if (!_s->buf) { \
+ pr_err(fmt, ##args); \
+ } else { \
+ int ret, len = _s->size - _s->used; \
+ ret = snprintf(_s->buf + _s->used, len, pr_fmt(fmt), ##args); \
+ _s->used += min(ret, len); \
+ } \
+})
+
+static void
+__ref_tracker_dir_pr_ostream(struct ref_tracker_dir *dir,
+ unsigned int display_limit, struct ostream *s)
+{
+ struct ref_tracker_dir_stats *stats;
+ unsigned int i = 0, skipped;
+ depot_stack_handle_t stack;
+ char *sbuf;
+
+ lockdep_assert_held(&dir->lock);
+
+ if (list_empty(&dir->list))
+ return;
+
+ stats = ref_tracker_get_stats(dir, display_limit);
+ if (IS_ERR(stats)) {
+ pr_ostream(s, "%s@%pK: couldn't get stats, error %pe\n",
+ dir->name, dir, stats);
+ return;
+ }
+
+ sbuf = kmalloc(STACK_BUF_SIZE, GFP_NOWAIT | __GFP_NOWARN);
+
+ for (i = 0, skipped = stats->total; i < stats->count; ++i) {
+ stack = stats->stacks[i].stack_handle;
+ if (sbuf && !stack_depot_snprint(stack, sbuf, STACK_BUF_SIZE, 4))
+ sbuf[0] = 0;
+ pr_ostream(s, "%s@%pK has %d/%d users at\n%s\n", dir->name, dir,
+ stats->stacks[i].count, stats->total, sbuf);
+ skipped -= stats->stacks[i].count;
+ }
+
+ if (skipped)
+ pr_ostream(s, "%s@%pK skipped reports about %d/%d users.\n",
+ dir->name, dir, skipped, stats->total);
+
+ kfree(sbuf);
+
+ kfree(stats);
+}
+
+void ref_tracker_dir_print_locked(struct ref_tracker_dir *dir,
+ unsigned int display_limit)
+{
+ struct ostream os = {};
+
+ __ref_tracker_dir_pr_ostream(dir, display_limit, &os);
+}
+EXPORT_SYMBOL(ref_tracker_dir_print_locked);
+
+void ref_tracker_dir_print(struct ref_tracker_dir *dir,
+ unsigned int display_limit)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&dir->lock, flags);
+ ref_tracker_dir_print_locked(dir, display_limit);
+ spin_unlock_irqrestore(&dir->lock, flags);
+}
+EXPORT_SYMBOL(ref_tracker_dir_print);
+
+int ref_tracker_dir_snprint(struct ref_tracker_dir *dir, char *buf, size_t size)
+{
+ struct ostream os = { .buf = buf, .size = size };
+ unsigned long flags;
+
+ spin_lock_irqsave(&dir->lock, flags);
+ __ref_tracker_dir_pr_ostream(dir, 16, &os);
+ spin_unlock_irqrestore(&dir->lock, flags);
+
+ return os.used;
+}
+EXPORT_SYMBOL(ref_tracker_dir_snprint);
+
+void ref_tracker_dir_exit(struct ref_tracker_dir *dir)
+{
+ struct ref_tracker *tracker, *n;
+ unsigned long flags;
+ bool leak = false;
+
+ dir->dead = true;
+ spin_lock_irqsave(&dir->lock, flags);
+ list_for_each_entry_safe(tracker, n, &dir->quarantine, head) {
+ list_del(&tracker->head);
+ kfree(tracker);
+ dir->quarantine_avail++;
+ }
+ if (!list_empty(&dir->list)) {
+ ref_tracker_dir_print_locked(dir, 16);
+ leak = true;
+ list_for_each_entry_safe(tracker, n, &dir->list, head) {
+ list_del(&tracker->head);
+ kfree(tracker);
+ }
+ }
+ spin_unlock_irqrestore(&dir->lock, flags);
+ WARN_ON_ONCE(leak);
+ WARN_ON_ONCE(refcount_read(&dir->untracked) != 1);
+ WARN_ON_ONCE(refcount_read(&dir->no_tracker) != 1);
+}
+EXPORT_SYMBOL(ref_tracker_dir_exit);
+
+int ref_tracker_alloc(struct ref_tracker_dir *dir,
+ struct ref_tracker **trackerp,
+ gfp_t gfp)
+{
+ unsigned long entries[REF_TRACKER_STACK_ENTRIES];
+ struct ref_tracker *tracker;
+ unsigned int nr_entries;
+ gfp_t gfp_mask = gfp | __GFP_NOWARN;
+ unsigned long flags;
+
+ WARN_ON_ONCE(dir->dead);
+
+ if (!trackerp) {
+ refcount_inc(&dir->no_tracker);
+ return 0;
+ }
+ if (gfp & __GFP_DIRECT_RECLAIM)
+ gfp_mask |= __GFP_NOFAIL;
+ *trackerp = tracker = kzalloc(sizeof(*tracker), gfp_mask);
+ if (unlikely(!tracker)) {
+ pr_err_once("memory allocation failure, unreliable refcount tracker.\n");
+ refcount_inc(&dir->untracked);
+ return -ENOMEM;
+ }
+ nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 1);
+ tracker->alloc_stack_handle = stack_depot_save(entries, nr_entries, gfp);
+
+ spin_lock_irqsave(&dir->lock, flags);
+ list_add(&tracker->head, &dir->list);
+ spin_unlock_irqrestore(&dir->lock, flags);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(ref_tracker_alloc);
+
+int ref_tracker_free(struct ref_tracker_dir *dir,
+ struct ref_tracker **trackerp)
+{
+ unsigned long entries[REF_TRACKER_STACK_ENTRIES];
+ depot_stack_handle_t stack_handle;
+ struct ref_tracker *tracker;
+ unsigned int nr_entries;
+ unsigned long flags;
+
+ WARN_ON_ONCE(dir->dead);
+
+ if (!trackerp) {
+ refcount_dec(&dir->no_tracker);
+ return 0;
+ }
+ tracker = *trackerp;
+ if (!tracker) {
+ refcount_dec(&dir->untracked);
+ return -EEXIST;
+ }
+ nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 1);
+ stack_handle = stack_depot_save(entries, nr_entries,
+ GFP_NOWAIT | __GFP_NOWARN);
+
+ spin_lock_irqsave(&dir->lock, flags);
+ if (tracker->dead) {
+ pr_err("reference already released.\n");
+ if (tracker->alloc_stack_handle) {
+ pr_err("allocated in:\n");
+ stack_depot_print(tracker->alloc_stack_handle);
+ }
+ if (tracker->free_stack_handle) {
+ pr_err("freed in:\n");
+ stack_depot_print(tracker->free_stack_handle);
+ }
+ spin_unlock_irqrestore(&dir->lock, flags);
+ WARN_ON_ONCE(1);
+ return -EINVAL;
+ }
+ tracker->dead = true;
+
+ tracker->free_stack_handle = stack_handle;
+
+ list_move_tail(&tracker->head, &dir->quarantine);
+ if (!dir->quarantine_avail) {
+ tracker = list_first_entry(&dir->quarantine, struct ref_tracker, head);
+ list_del(&tracker->head);
+ } else {
+ dir->quarantine_avail--;
+ tracker = NULL;
+ }
+ spin_unlock_irqrestore(&dir->lock, flags);
+
+ kfree(tracker);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(ref_tracker_free);