[PATCH 1/1] lib: add version into /proc/allocinfo output

[Suren Baghdasaryan <surenb@google.com>]

Add version string at the beginning of /proc/allocinfo to allow later
format changes. Exampe output:

> head /proc/allocinfo
allocinfo - version: 1.0
           0        0 init/main.c:1314 func:do_initcalls
           0        0 init/do_mounts.c:353 func:mount_nodev_root
           0        0 init/do_mounts.c:187 func:mount_root_generic
           0        0 init/do_mounts.c:158 func:do_mount_root
           0        0 init/initramfs.c:493 func:unpack_to_rootfs
           0        0 init/initramfs.c:492 func:unpack_to_rootfs
           0        0 init/initramfs.c:491 func:unpack_to_rootfs
         512        1 arch/x86/events/rapl.c:681 func:init_rapl_pmus
         128        1 arch/x86/events/rapl.c:571 func:rapl_cpu_online

Signed-off-by: Suren Baghdasaryan <surenb@google.com>
---
 Documentation/filesystems/proc.rst |  4 +--
 lib/alloc_tag.c                    | 42 +++++++++++++++++++-----------
 2 files changed, 29 insertions(+), 17 deletions(-)

diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst
index 245269dd6e02..97d76adb1ecf 100644
--- a/Documentation/filesystems/proc.rst
+++ b/Documentation/filesystems/proc.rst
@@ -961,13 +961,13 @@ Provides information about memory allocations at all locations in the code
 base. Each allocation in the code is identified by its source file, line
 number, module (if originates from a loadable module) and the function calling
 the allocation. The number of bytes allocated and number of calls at each
-location are reported.
+location are reported. The first line indicates the version of the file.
 
 Example output.
 
 ::
 
-    > sort -rn /proc/allocinfo
+    > tail -n +2 /proc/allocinfo | sort -rn
    127664128    31168 mm/page_ext.c:270 func:alloc_page_ext
     56373248     4737 mm/slub.c:2259 func:alloc_slab_page
     14880768     3633 mm/readahead.c:247 func:page_cache_ra_unbounded
diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
index 531dbe2f5456..777b5cebf9a4 100644
--- a/lib/alloc_tag.c
+++ b/lib/alloc_tag.c
@@ -16,44 +16,51 @@ EXPORT_SYMBOL(_shared_alloc_tag);
 DEFINE_STATIC_KEY_MAYBE(CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT,
 			mem_alloc_profiling_key);
 
+struct allocinfo_private {
+	struct codetag_iterator iter;
+	bool print_header;
+
+};
+
 static void *allocinfo_start(struct seq_file *m, loff_t *pos)
 {
-	struct codetag_iterator *iter;
+	struct allocinfo_private *priv;
 	struct codetag *ct;
 	loff_t node = *pos;
 
-	iter = kzalloc(sizeof(*iter), GFP_KERNEL);
-	m->private = iter;
-	if (!iter)
+	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
+	m->private = priv;
+	if (!priv)
 		return NULL;
 
+	priv->print_header = (node == 0);
 	codetag_lock_module_list(alloc_tag_cttype, true);
-	*iter = codetag_get_ct_iter(alloc_tag_cttype);
-	while ((ct = codetag_next_ct(iter)) != NULL && node)
+	priv->iter = codetag_get_ct_iter(alloc_tag_cttype);
+	while ((ct = codetag_next_ct(&priv->iter)) != NULL && node)
 		node--;
 
-	return ct ? iter : NULL;
+	return ct ? priv : NULL;
 }
 
 static void *allocinfo_next(struct seq_file *m, void *arg, loff_t *pos)
 {
-	struct codetag_iterator *iter = (struct codetag_iterator *)arg;
-	struct codetag *ct = codetag_next_ct(iter);
+	struct allocinfo_private *priv = (struct allocinfo_private *)arg;
+	struct codetag *ct = codetag_next_ct(&priv->iter);
 
 	(*pos)++;
 	if (!ct)
 		return NULL;
 
-	return iter;
+	return priv;
 }
 
 static void allocinfo_stop(struct seq_file *m, void *arg)
 {
-	struct codetag_iterator *iter = (struct codetag_iterator *)m->private;
+	struct allocinfo_private *priv = (struct allocinfo_private *)m->private;
 
-	if (iter) {
+	if (priv) {
 		codetag_lock_module_list(alloc_tag_cttype, false);
-		kfree(iter);
+		kfree(priv);
 	}
 }
 
@@ -71,13 +78,18 @@ static void alloc_tag_to_text(struct seq_buf *out, struct codetag *ct)
 
 static int allocinfo_show(struct seq_file *m, void *arg)
 {
-	struct codetag_iterator *iter = (struct codetag_iterator *)arg;
+	struct allocinfo_private *priv = (struct allocinfo_private *)arg;
 	char *bufp;
 	size_t n = seq_get_buf(m, &bufp);
 	struct seq_buf buf;
 
 	seq_buf_init(&buf, bufp, n);
-	alloc_tag_to_text(&buf, iter->ct);
+	if (priv->print_header) {
+		/* Output format version, so we can change it. */
+		seq_buf_printf(&buf, "allocinfo - version: 1.0\n");
+		priv->print_header = false;
+	}
+	alloc_tag_to_text(&buf, priv->iter.ct);
 	seq_commit(m, seq_buf_used(&buf));
 	return 0;
 }

base-commit: 7e8aafe0636cdcc5c9699ced05ff1f8ffcb937e2
-- 
2.45.0.rc1.225.g2a3ae87e7f-goog