[PATCH v4 03/10] lib/ref_tracker: add printing to memory buffer

[Andrzej Hajda]

In case one wants to show stats via debugfs.

Signed-off-by: Andrzej Hajda <andrzej.ha...@intel.com>
---
 include/linux/ref_tracker.h |  8 +++++++
 lib/ref_tracker.c           | 56 ++++++++++++++++++++++++++++++++++++++-------
 2 files changed, 56 insertions(+), 8 deletions(-)

diff --git a/include/linux/ref_tracker.h b/include/linux/ref_tracker.h
index a2cf1f6309adb2..2fdbfd2e14797a 100644
--- a/include/linux/ref_tracker.h
+++ b/include/linux/ref_tracker.h
@@ -50,6 +50,8 @@ void __ref_tracker_dir_print(struct ref_tracker_dir *dir,
 void ref_tracker_dir_print(struct ref_tracker_dir *dir,
                           unsigned int display_limit);
 
+int ref_tracker_dir_snprint(struct ref_tracker_dir *dir, char *buf, size_t 
size);
+
 int ref_tracker_alloc(struct ref_tracker_dir *dir,
                      struct ref_tracker **trackerp, gfp_t gfp);
 
@@ -78,6 +80,12 @@ static inline void ref_tracker_dir_print(struct 
ref_tracker_dir *dir,
 {
 }
 
+static inline int ref_tracker_dir_snprint(struct ref_tracker_dir *dir,
+                                         char *buf, size_t size)
+{
+       return 0;
+}
+
 static inline int ref_tracker_alloc(struct ref_tracker_dir *dir,
                                    struct ref_tracker **trackerp,
                                    gfp_t gfp)
diff --git a/lib/ref_tracker.c b/lib/ref_tracker.c
index ab1253fde244ea..2ef4596b6b36f5 100644
--- a/lib/ref_tracker.c
+++ b/lib/ref_tracker.c
@@ -62,8 +62,27 @@ ref_tracker_get_stats(struct ref_tracker_dir *dir, unsigned 
int limit)
        return stats;
 }
 
-void __ref_tracker_dir_print(struct ref_tracker_dir *dir,
-                          unsigned int display_limit)
+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;
@@ -77,8 +96,8 @@ void __ref_tracker_dir_print(struct ref_tracker_dir *dir,
 
        stats = ref_tracker_get_stats(dir, display_limit);
        if (IS_ERR(stats)) {
-               pr_err("%s@%pK: couldn't get stats, error %pe\n",
-                      dir->name, dir, stats);
+               pr_ostream(s, "%s@%pK: couldn't get stats, error %pe\n",
+                          dir->name, dir, stats);
                return;
        }
 
@@ -88,19 +107,27 @@ void __ref_tracker_dir_print(struct ref_tracker_dir *dir,
                stack = stats->stacks[i].stack_handle;
                if (sbuf && !stack_depot_snprint(stack, sbuf, STACK_BUF_SIZE, 
4))
                        sbuf[0] = 0;
-               pr_err("%s@%pK has %d/%d users at\n%s\n", dir->name, dir,
-                      stats->stacks[i].count, stats->total, sbuf);
+               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_err("%s@%pK skipped reports about %d/%d users.\n",
-                      dir->name, dir, skipped, stats->total);
+               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(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);
 
 void ref_tracker_dir_print(struct ref_tracker_dir *dir,
@@ -114,6 +141,19 @@ void ref_tracker_dir_print(struct ref_tracker_dir *dir,
 }
 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;

-- 
2.34.1