linux-kernel - Re: [PATCH] lib/scatterlist: Avoid a double memset

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Message-ID: <alpine.DEB.2.22.394.2009201032080.2966@hadrien>
Date:   Sun, 20 Sep 2020 10:32:54 +0200 (CEST)
From:   Julia Lawall <julia.lawall@...ia.fr>
To:     Joe Perches <joe@...ches.com>
cc:     Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        akpm@...ux-foundation.org, natechancellor@...il.com,
        geert+renesas@...der.be, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] lib/scatterlist: Avoid a double memset



On Sun, 20 Sep 2020, Joe Perches wrote:

> On Sun, 2020-09-20 at 09:15 +0200, Christophe JAILLET wrote:
> > 'sgl' is zeroed a few lines below in 'sg_init_table()'. There is no need to
> > clear it twice.
> >
> > Remove the redundant initialization.
>
> I didn't look very thoroughly, but there are at least
> a few more of these with kcalloc and kzalloc like
>
> block/bsg-lib.c-        size_t sz = (sizeof(struct scatterlist) * req->nr_phys_segments);
> block/bsg-lib.c-
> block/bsg-lib.c-        BUG_ON(!req->nr_phys_segments);
> block/bsg-lib.c-
> block/bsg-lib.c-        buf->sg_list = kzalloc(sz, GFP_KERNEL);
> block/bsg-lib.c-        if (!buf->sg_list)
> block/bsg-lib.c-                return -ENOMEM;
> block/bsg-lib.c:        sg_init_table(buf->sg_list, req->nr_phys_segments);
> ---
> drivers/target/target_core_rd.c-		sg = kcalloc(sg_per_table + chain_entry, sizeof(*sg),
> drivers/target/target_core_rd.c-				GFP_KERNEL);
> drivers/target/target_core_rd.c-		if (!sg)
> drivers/target/target_core_rd.c-			return -ENOMEM;
> drivers/target/target_core_rd.c-
> drivers/target/target_core_rd.c:		sg_init_table(sg, sg_per_table + chain_entry);
> ---
> net/rds/rdma.c-		sg = kcalloc(nents, sizeof(*sg), GFP_KERNEL);
> net/rds/rdma.c-		if (!sg) {
> net/rds/rdma.c-			ret = -ENOMEM;
> net/rds/rdma.c-			goto out;
> net/rds/rdma.c-		}
> net/rds/rdma.c-		WARN_ON(!nents);
> net/rds/rdma.c:		sg_init_table(sg, nents);

I found 16 occurrences in the following files:

net/rds/rdma.c
drivers/infiniband/hw/efa/efa_verbs.c
drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
drivers/misc/mic/scif/scif_nodeqp.c
block/bsg-lib.c
drivers/dma/sh/rcar-dmac.c
drivers/spi/spi-topcliff-pch.c
net/sunrpc/xprtrdma/frwr_ops.c
drivers/dma/imx-dma.c
drivers/pci/p2pdma.c
drivers/dma/sh/shdma-base.c
drivers/target/target_core_rd.c
drivers/media/common/saa7146/saa7146_core.c
drivers/tty/serial/pch_uart.c
drivers/net/wireless/intel/iwlwifi/fw/dbg.c

julia