linux-kernel - [PATCH 4/4] IB/mthca: Use non-atomic bitmap functions when possible in 'mthca

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Date:   Wed, 24 Nov 2021 21:43:35 +0100
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     dledford@...hat.com, jgg@...pe.ca
Cc:     linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>
Subject: [PATCH 4/4] IB/mthca: Use non-atomic bitmap functions when possible in 'mthca_mr.c'

In 'mthca_buddy_init()', the 'buddy->bits[n]' bitmap has just been
allocated, so no concurrent accesses can occur.

The other accesses to the 'buddy->bits[n]' bitmap are protected by the
'buddy->lock' spinlock, so no concurrent accesses can occur.

So prefer the non-atomic '__[set|clear]_bit()' functions to save a few
cycles.

Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
---
 drivers/infiniband/hw/mthca/mthca_mr.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/infiniband/hw/mthca/mthca_mr.c b/drivers/infiniband/hw/mthca/mthca_mr.c
index 8892fcdbac4c..a59100c496b4 100644
--- a/drivers/infiniband/hw/mthca/mthca_mr.c
+++ b/drivers/infiniband/hw/mthca/mthca_mr.c
@@ -101,13 +101,13 @@ static u32 mthca_buddy_alloc(struct mthca_buddy *buddy, int order)
 	return -1;
 
  found:
-	clear_bit(seg, buddy->bits[o]);
+	__clear_bit(seg, buddy->bits[o]);
 	--buddy->num_free[o];
 
 	while (o > order) {
 		--o;
 		seg <<= 1;
-		set_bit(seg ^ 1, buddy->bits[o]);
+		__set_bit(seg ^ 1, buddy->bits[o]);
 		++buddy->num_free[o];
 	}
 
@@ -125,13 +125,13 @@ static void mthca_buddy_free(struct mthca_buddy *buddy, u32 seg, int order)
 	spin_lock(&buddy->lock);
 
 	while (test_bit(seg ^ 1, buddy->bits[order])) {
-		clear_bit(seg ^ 1, buddy->bits[order]);
+		__clear_bit(seg ^ 1, buddy->bits[order]);
 		--buddy->num_free[order];
 		seg >>= 1;
 		++order;
 	}
 
-	set_bit(seg, buddy->bits[order]);
+	__set_bit(seg, buddy->bits[order]);
 	++buddy->num_free[order];
 
 	spin_unlock(&buddy->lock);
@@ -158,7 +158,7 @@ static int mthca_buddy_init(struct mthca_buddy *buddy, int max_order)
 			goto err_out_free;
 	}
 
-	set_bit(0, buddy->bits[buddy->max_order]);
+	__set_bit(0, buddy->bits[buddy->max_order]);
 	buddy->num_free[buddy->max_order] = 1;
 
 	return 0;
-- 
2.30.2