netdev - [PATCH net-next 02/14] lib: cpu_rmap: Use allocator for rmap entries

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Date:   Sun, 19 Feb 2023 22:14:30 -0800
From:   Saeed Mahameed <saeed@...nel.org>
To:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Eric Dumazet <edumazet@...gle.com>
Cc:     Saeed Mahameed <saeedm@...dia.com>, netdev@...r.kernel.org,
        Tariq Toukan <tariqt@...dia.com>, Eli Cohen <elic@...dia.com>,
        Ben Hutchings <bhutchings@...arflare.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Decotigny <decot@...glers.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH net-next 02/14] lib: cpu_rmap: Use allocator for rmap entries

From: Eli Cohen <elic@...dia.com>

Use a proper allocator for rmap entries using a naive for loop. The
allocator relies on whether an entry is NULL to be considered free.
Remove the used field of rmap which is not needed.

Also, avoid crashing the kernel if an entry is not available.

CC: Ben Hutchings <bhutchings@...arflare.com>
CC: Andrew Morton <akpm@...ux-foundation.org>
CC: David Decotigny <decot@...glers.com>
CC: Eric Dumazet <edumazet@...gle.com>
CC: linux-kernel@...r.kernel.org
Signed-off-by: Eli Cohen <elic@...dia.com>
Signed-off-by: Saeed Mahameed <saeedm@...dia.com>
---
 include/linux/cpu_rmap.h |  3 +--
 lib/cpu_rmap.c           | 23 +++++++++++++++++++----
 2 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/include/linux/cpu_rmap.h b/include/linux/cpu_rmap.h
index be8aea04d023..0ec745e6cd36 100644
--- a/include/linux/cpu_rmap.h
+++ b/include/linux/cpu_rmap.h
@@ -16,14 +16,13 @@
  * struct cpu_rmap - CPU affinity reverse-map
  * @refcount: kref for object
  * @size: Number of objects to be reverse-mapped
- * @used: Number of objects added
  * @obj: Pointer to array of object pointers
  * @near: For each CPU, the index and distance to the nearest object,
  *      based on affinity masks
  */
 struct cpu_rmap {
 	struct kref	refcount;
-	u16		size, used;
+	u16		size;
 	void		**obj;
 	struct {
 		u16	index;
diff --git a/lib/cpu_rmap.c b/lib/cpu_rmap.c
index e77f12bb3c77..e95d018e01c2 100644
--- a/lib/cpu_rmap.c
+++ b/lib/cpu_rmap.c
@@ -128,6 +128,17 @@ debug_print_rmap(const struct cpu_rmap *rmap, const char *prefix)
 }
 #endif
 
+static int get_free_index(struct cpu_rmap *rmap)
+{
+	int i;
+
+	for (i = 0; i < rmap->size; i++)
+		if (!rmap->obj[i])
+			return i;
+
+	return -1;
+}
+
 /**
  * cpu_rmap_add - add object to a rmap
  * @rmap: CPU rmap allocated with alloc_cpu_rmap()
@@ -137,10 +148,11 @@ debug_print_rmap(const struct cpu_rmap *rmap, const char *prefix)
  */
 int cpu_rmap_add(struct cpu_rmap *rmap, void *obj)
 {
-	u16 index;
+	u16 index = get_free_index(rmap);
+
+	if (index == -1)
+		return index;
 
-	BUG_ON(rmap->used >= rmap->size);
-	index = rmap->used++;
 	rmap->obj[index] = obj;
 	return index;
 }
@@ -230,7 +242,7 @@ void free_irq_cpu_rmap(struct cpu_rmap *rmap)
 	if (!rmap)
 		return;
 
-	for (index = 0; index < rmap->used; index++) {
+	for (index = 0; index < rmap->size; index++) {
 		glue = rmap->obj[index];
 		if (glue)
 			irq_set_affinity_notifier(glue->notify.irq, NULL);
@@ -296,6 +308,9 @@ int irq_cpu_rmap_add(struct cpu_rmap *rmap, int irq)
 	glue->rmap = rmap;
 	cpu_rmap_get(rmap);
 	glue->index = cpu_rmap_add(rmap, glue);
+	if (glue->index == -1)
+		return -ENOSPC;
+
 	rc = irq_set_affinity_notifier(irq, &glue->notify);
 	if (rc) {
 		cpu_rmap_put(glue->rmap);
-- 
2.39.1