linux-kernel - [PATCH 4/5] octeontx2-af: Fix the size of memory allocated for the 'id

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Date:   Fri, 25 Nov 2022 13:24:00 +0100
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     Sunil Goutham <sgoutham@...vell.com>,
        Linu Cherian <lcherian@...vell.com>,
        Geetha sowjanya <gakula@...vell.com>,
        Jerin Jacob <jerinj@...vell.com>,
        hariprasad <hkelam@...vell.com>,
        Subbaraya Sundeep <sbhatta@...vell.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        netdev@...r.kernel.org
Subject: [PATCH 4/5] octeontx2-af: Fix the size of memory allocated for the 'id_bmap' bitmap

This allocation is really spurious.
The size of the bitmap is 'tot_ids' and it is used as such in the driver.

So we could expect something like:
   table->id_bmap = devm_kcalloc(rvu->dev, BITS_TO_LONGS(table->tot_ids),
			         sizeof(long), GFP_KERNEL);

However, when the bitmap is allocated, we allocate:
   BITS_TO_LONGS(table->tot_ids) * table->tot_ids ~=
   table->tot_ids / 32 * table->tot_ids ~=
   table->tot_ids^2 / 32

It is proportional to the square of 'table->tot_ids' which seems to
potentially be big.

Allocate the expected amount of memory, and switch to the bitmap API to
have it more straightforward.

Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
---
This patch is speculative.

If I'm right, I'm curious to know if 'able->tot_ids' can really get big
(I'm just guessing) , and if yes, how much.
---
 drivers/net/ethernet/marvell/octeontx2/af/rvu_npc_hash.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/marvell/octeontx2/af/rvu_npc_hash.c b/drivers/net/ethernet/marvell/octeontx2/af/rvu_npc_hash.c
index 3f94b620ef5a..ae34746341c4 100644
--- a/drivers/net/ethernet/marvell/octeontx2/af/rvu_npc_hash.c
+++ b/drivers/net/ethernet/marvell/octeontx2/af/rvu_npc_hash.c
@@ -1914,8 +1914,8 @@ int rvu_npc_exact_init(struct rvu *rvu)
 	dev_dbg(rvu->dev, "%s: Allocated bitmap for 32 entry cam\n", __func__);
 
 	table->tot_ids = (table->mem_table.depth * table->mem_table.ways) + table->cam_table.depth;
-	table->id_bmap = devm_kcalloc(rvu->dev, BITS_TO_LONGS(table->tot_ids),
-				      table->tot_ids, GFP_KERNEL);
+	table->id_bmap = devm_bitmap_zalloc(rvu->dev, table->tot_ids,
+					    GFP_KERNEL);
 
 	if (!table->id_bmap)
 		return -ENOMEM;
-- 
2.34.1