diff mbox series

[net-next,8/8] net: add napi_get_frags_check() helper

Message ID 20220607171732.21191-9-eric.dumazet@gmail.com (mailing list archive)
State Superseded
Delegated to: Netdev Maintainers
Headers show
Series net: few debug refinements | expand

Checks

Context Check Description
netdev/tree_selection success Clearly marked for net-next
netdev/fixes_present success Fixes tag not required for -next series
netdev/subject_prefix success Link
netdev/cover_letter success Series has a cover letter
netdev/patch_count success Link
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 7 this patch: 7
netdev/cc_maintainers success CCed 5 of 5 maintainers
netdev/build_clang success Errors and warnings before: 6 this patch: 6
netdev/module_param success Was 0 now: 0
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 7 this patch: 7
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 30 lines checked
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0

Commit Message

Eric Dumazet June 7, 2022, 5:17 p.m. UTC 
From: Eric Dumazet <edumazet@google.com>

This is a follow up of commit 3226b158e67c
("net: avoid 32 x truesize under-estimation for tiny skbs")

When/if we increase MAX_SKB_FRAGS, we better make sure
the old bug will not come back.

Adding a check in napi_get_frags() would be costly,
even if using DEBUG_NET_WARN_ON_ONCE().

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/core/dev.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)
diff mbox series

Patch

diff --git a/net/core/dev.c b/net/core/dev.c
index 27ad09ad80a4550097ce4d113719a558b5e2a811..4ce9b2563a116066d85bae7a862e38fb160ef0e2 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6351,6 +6351,23 @@  int dev_set_threaded(struct net_device *dev, bool threaded)
 }
 EXPORT_SYMBOL(dev_set_threaded);
 
+/* Double check that napi_get_frags() allocates skbs with
+ * skb->head being backed by slab, not a page fragment.
+ * This is to make sure bug fixed in 3226b158e67c
+ * ("net: avoid 32 x truesize under-estimation for tiny skbs")
+ * does not accidentally come back.
+ */
+static void napi_get_frags_check(struct napi_struct *napi)
+{
+	struct sk_buff *skb;
+
+	local_bh_disable();
+	skb = napi_get_frags(napi);
+	WARN_ON_ONCE(skb && skb->head_frag);
+	napi_free_frags(napi);
+	local_bh_enable();
+}
+
 void netif_napi_add_weight(struct net_device *dev, struct napi_struct *napi,
 			   int (*poll)(struct napi_struct *, int), int weight)
 {
@@ -6378,6 +6395,7 @@  void netif_napi_add_weight(struct net_device *dev, struct napi_struct *napi,
 	set_bit(NAPI_STATE_NPSVC, &napi->state);
 	list_add_rcu(&napi->dev_list, &dev->napi_list);
 	napi_hash_add(napi);
+	napi_get_frags_check(napi);
 	/* Create kthread for this napi if dev->threaded is set.
 	 * Clear dev->threaded if kthread creation failed so that
 	 * threaded mode will not be enabled in napi_enable().