netdev - [PATCH net-next 1/6] net: mm_account_pinned

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Message-ID: <20221115091101.2234482-2-edumazet@google.com>
Date:   Tue, 15 Nov 2022 09:10:56 +0000
From:   Eric Dumazet <edumazet@...gle.com>
To:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     netdev@...r.kernel.org, eric.dumazet@...il.com,
        Eric Dumazet <edumazet@...gle.com>,
        Willem de Bruijn <willemb@...gle.com>
Subject: [PATCH net-next 1/6] net: mm_account_pinned_pages() optimization

Adopt atomic_long_try_cmpxchg() in mm_account_pinned_pages()
as it is slightly more efficient.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Willem de Bruijn <willemb@...gle.com>
---
 net/core/skbuff.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 90d085290d49d864b8431f99a19dbda867d9c03b..4bf95e36ed162611e8245c64c6caeecf9f60ef5d 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -1267,13 +1267,12 @@ int mm_account_pinned_pages(struct mmpin *mmp, size_t size)
 	max_pg = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
 	user = mmp->user ? : current_user();
 
+	old_pg = atomic_long_read(&user->locked_vm);
 	do {
-		old_pg = atomic_long_read(&user->locked_vm);
 		new_pg = old_pg + num_pg;
 		if (new_pg > max_pg)
 			return -ENOBUFS;
-	} while (atomic_long_cmpxchg(&user->locked_vm, old_pg, new_pg) !=
-		 old_pg);
+	} while (!atomic_long_try_cmpxchg(&user->locked_vm, &old_pg, new_pg));
 
 	if (!mmp->user) {
 		mmp->user = get_uid(user);
-- 
2.38.1.431.g37b22c650d-goog