linux-kernel - [PATCH] aio: Save a few cycles in 'lookup

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Message-Id: <0c3fcdaec33bb12b2367860dfab7ed4224ea000c.1635974999.git.christophe.jaillet@wanadoo.fr>
Date:   Wed,  3 Nov 2021 22:31:35 +0100
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     bcrl@...ck.org, viro@...iv.linux.org.uk
Cc:     linux-aio@...ck.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>
Subject: [PATCH] aio: Save a few cycles in 'lookup_ioctx()'

Use 'percpu_ref_tryget_live_rcu()' instead of 'percpu_ref_tryget_live()' to
save a few cycles when it is known that the rcu lock is already
taken/released.

Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
---
 fs/aio.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/aio.c b/fs/aio.c
index 9c81cf611d65..d189ea13e10a 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1062,7 +1062,7 @@ static struct kioctx *lookup_ioctx(unsigned long ctx_id)
 	id = array_index_nospec(id, table->nr);
 	ctx = rcu_dereference(table->table[id]);
 	if (ctx && ctx->user_id == ctx_id) {
-		if (percpu_ref_tryget_live(&ctx->users))
+		if (percpu_ref_tryget_live_rcu(&ctx->users))
 			ret = ctx;
 	}
 out:
-- 
2.30.2