[PATCH] wlcore: consolidate kmalloc + memset 0 into kzalloc

[PATCH] wlcore: consolidate kmalloc + memset 0 into kzalloc

[Nicholas Mc Guire]

This is an API consolidation only. The use of kmalloc + memset to 0
is equivalent to kzalloc.

Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
---

Found by coccinelle script (relaxed version of
scripts/coccinelle/api/alloc/kzalloc-simple.cocci)

Patch was compile tested with: x86_64_defconfig +
CONFIG_WL12XX=m (implies CONFIG_WLCORE=m)

Patch is against linux-next (localversion-next is -next-20151221)

 drivers/net/wireless/ti/wlcore/main.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/net/wireless/ti/wlcore/main.c b/drivers/net/wireless/ti/wlcore/main.c
index ec7f6af..dfc49bf 100644
--- a/drivers/net/wireless/ti/wlcore/main.c
+++ b/drivers/net/wireless/ti/wlcore/main.c
@@ -838,7 +838,7 @@ static void wl12xx_read_fwlog_panic(struct wl1271 *wl)
 
 	wl1271_info("Reading FW panic log");
 
-	block = kmalloc(wl->fw_mem_block_size, GFP_KERNEL);
+	block = kzalloc(wl->fw_mem_block_size, GFP_KERNEL);
 	if (!block)
 		return;
 
@@ -885,7 +885,6 @@ static void wl12xx_read_fwlog_panic(struct wl1271 *wl)
 			goto out;
 		}
 
-		memset(block, 0, wl->fw_mem_block_size);
 		ret = wlcore_read_hwaddr(wl, addr, block,
 					wl->fw_mem_block_size, false);
 
-- 
2.1.4

Re: [PATCH] wlcore: consolidate kmalloc + memset 0 into kzalloc

[Julian Calaby]

Hi,

On Tue, Dec 22, 2015 at 3:47 AM, Nicholas Mc Guire <hofrat@osadl.org> wrote:
> This is an API consolidation only. The use of kmalloc + memset to 0
> is equivalent to kzalloc.
>
> Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
> ---
>
> Found by coccinelle script (relaxed version of
> scripts/coccinelle/api/alloc/kzalloc-simple.cocci)
>
> Patch was compile tested with: x86_64_defconfig +
> CONFIG_WL12XX=m (implies CONFIG_WLCORE=m)
>
> Patch is against linux-next (localversion-next is -next-20151221)
>
>  drivers/net/wireless/ti/wlcore/main.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/net/wireless/ti/wlcore/main.c b/drivers/net/wireless/ti/wlcore/main.c
> index ec7f6af..dfc49bf 100644
> --- a/drivers/net/wireless/ti/wlcore/main.c
> +++ b/drivers/net/wireless/ti/wlcore/main.c
> @@ -838,7 +838,7 @@ static void wl12xx_read_fwlog_panic(struct wl1271 *wl)
>
>         wl1271_info("Reading FW panic log");
>
> -       block = kmalloc(wl->fw_mem_block_size, GFP_KERNEL);
> +       block = kzalloc(wl->fw_mem_block_size, GFP_KERNEL);
>         if (!block)
>                 return;
>
> @@ -885,7 +885,6 @@ static void wl12xx_read_fwlog_panic(struct wl1271 *wl)
>                         goto out;
>                 }
> -               memset(block, 0, wl->fw_mem_block_size);

I don't think you can't remove this line. It appears that the loop
this is part of resets block to be all zero, reads a chunk of data in,
then operates on it. I'm guessing that the code after the following
line expects that there isn't any data left over from previous runs
through the loop.

>                 ret = wlcore_read_hwaddr(wl, addr, block,
>                                         wl->fw_mem_block_size, false);
>
> --
> 2.1.4
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-wireless" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html



-- 
Julian Calaby

Email: julian.calaby@gmail.com
Profile: http://www.google.com/profiles/julian.calaby/

Re: [PATCH] wlcore: consolidate kmalloc + memset 0 into kzalloc

[Souptick Joarder]

On Mon, Dec 21, 2015 at 10:17 PM, Nicholas Mc Guire <hofrat@osadl.org> wrote:
> This is an API consolidation only. The use of kmalloc + memset to 0
> is equivalent to kzalloc.
>
> Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
> ---
>
> Found by coccinelle script (relaxed version of
> scripts/coccinelle/api/alloc/kzalloc-simple.cocci)
>
> Patch was compile tested with: x86_64_defconfig +
> CONFIG_WL12XX=m (implies CONFIG_WLCORE=m)
>
> Patch is against linux-next (localversion-next is -next-20151221)
>
>  drivers/net/wireless/ti/wlcore/main.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/net/wireless/ti/wlcore/main.c b/drivers/net/wireless/ti/wlcore/main.c
> index ec7f6af..dfc49bf 100644
> --- a/drivers/net/wireless/ti/wlcore/main.c
> +++ b/drivers/net/wireless/ti/wlcore/main.c
> @@ -838,7 +838,7 @@ static void wl12xx_read_fwlog_panic(struct wl1271 *wl)
>
>         wl1271_info("Reading FW panic log");
>
> -       block = kmalloc(wl->fw_mem_block_size, GFP_KERNEL);
> +       block = kzalloc(wl->fw_mem_block_size, GFP_KERNEL);
>         if (!block)
>                 return;
>
> @@ -885,7 +885,6 @@ static void wl12xx_read_fwlog_panic(struct wl1271 *wl)
>                         goto out;
>                 }
>
> -               memset(block, 0, wl->fw_mem_block_size);

Current code is reseting the block value to 0 in each iterations and
perform some operations.
But if you are using kzalloc as mentioned above it will memset 0 to
block pointer only once.
So both are not equivalent operations.

>                 ret = wlcore_read_hwaddr(wl, addr, block,
>                                         wl->fw_mem_block_size, false);
>
> --
> 2.1.4
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-wireless" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

-Souptick

Re: [PATCH] wlcore: consolidate kmalloc + memset 0 into kzalloc

[Nicholas Mc Guire]

On Tue, Dec 22, 2015 at 09:56:10AM +1100, Julian Calaby wrote:
> Hi,
> 
> On Tue, Dec 22, 2015 at 3:47 AM, Nicholas Mc Guire <hofrat@osadl.org> wrote:
> > This is an API consolidation only. The use of kmalloc + memset to 0
> > is equivalent to kzalloc.
> >
> > Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
> > ---
> >
> > Found by coccinelle script (relaxed version of
> > scripts/coccinelle/api/alloc/kzalloc-simple.cocci)
> >
> > Patch was compile tested with: x86_64_defconfig +
> > CONFIG_WL12XX=m (implies CONFIG_WLCORE=m)
> >
> > Patch is against linux-next (localversion-next is -next-20151221)
> >
> >  drivers/net/wireless/ti/wlcore/main.c | 3 +--
> >  1 file changed, 1 insertion(+), 2 deletions(-)
> >
> > diff --git a/drivers/net/wireless/ti/wlcore/main.c b/drivers/net/wireless/ti/wlcore/main.c
> > index ec7f6af..dfc49bf 100644
> > --- a/drivers/net/wireless/ti/wlcore/main.c
> > +++ b/drivers/net/wireless/ti/wlcore/main.c
> > @@ -838,7 +838,7 @@ static void wl12xx_read_fwlog_panic(struct wl1271 *wl)
> >
> >         wl1271_info("Reading FW panic log");
> >
> > -       block = kmalloc(wl->fw_mem_block_size, GFP_KERNEL);
> > +       block = kzalloc(wl->fw_mem_block_size, GFP_KERNEL);
> >         if (!block)
> >                 return;
> >
> > @@ -885,7 +885,6 @@ static void wl12xx_read_fwlog_panic(struct wl1271 *wl)
> >                         goto out;
> >                 }
> > -               memset(block, 0, wl->fw_mem_block_size);
> 
> I don't think you can't remove this line. It appears that the loop
> this is part of resets block to be all zero, reads a chunk of data in,
> then operates on it. I'm guessing that the code after the following
> line expects that there isn't any data left over from previous runs
> through the loop.
>
the rational for this being ok is thta the copy operation into block is: 
                ret = wlcore_read_hwaddr(wl, addr, block,
                                        wl->fw_mem_block_size, false);

this will end up in the .read methods where block should be completely 
overwritten (length == full block size), so within the loop if successful
this should be correct - if not successful it would "goto out" witout 
using the content of block.

Am I overlooking something here ?

thx!
hofrat

Re: [PATCH] wlcore: consolidate kmalloc + memset 0 into kzalloc

[Julian Calaby]

Hi Nicholas,

On Tue, Dec 22, 2015 at 6:29 PM, Nicholas Mc Guire <der.herr@hofr.at> wrote:
> On Tue, Dec 22, 2015 at 09:56:10AM +1100, Julian Calaby wrote:
>> Hi,
>>
>> On Tue, Dec 22, 2015 at 3:47 AM, Nicholas Mc Guire <hofrat@osadl.org> wrote:
>> > This is an API consolidation only. The use of kmalloc + memset to 0
>> > is equivalent to kzalloc.
>> >
>> > Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
>> > ---
>> >
>> > Found by coccinelle script (relaxed version of
>> > scripts/coccinelle/api/alloc/kzalloc-simple.cocci)
>> >
>> > Patch was compile tested with: x86_64_defconfig +
>> > CONFIG_WL12XX=m (implies CONFIG_WLCORE=m)
>> >
>> > Patch is against linux-next (localversion-next is -next-20151221)
>> >
>> >  drivers/net/wireless/ti/wlcore/main.c | 3 +--
>> >  1 file changed, 1 insertion(+), 2 deletions(-)
>> >
>> > diff --git a/drivers/net/wireless/ti/wlcore/main.c b/drivers/net/wireless/ti/wlcore/main.c
>> > index ec7f6af..dfc49bf 100644
>> > --- a/drivers/net/wireless/ti/wlcore/main.c
>> > +++ b/drivers/net/wireless/ti/wlcore/main.c
>> > @@ -838,7 +838,7 @@ static void wl12xx_read_fwlog_panic(struct wl1271 *wl)
>> >
>> >         wl1271_info("Reading FW panic log");
>> >
>> > -       block = kmalloc(wl->fw_mem_block_size, GFP_KERNEL);
>> > +       block = kzalloc(wl->fw_mem_block_size, GFP_KERNEL);
>> >         if (!block)
>> >                 return;
>> >
>> > @@ -885,7 +885,6 @@ static void wl12xx_read_fwlog_panic(struct wl1271 *wl)
>> >                         goto out;
>> >                 }
>> > -               memset(block, 0, wl->fw_mem_block_size);
>>
>> I don't think you can't remove this line. It appears that the loop
>> this is part of resets block to be all zero, reads a chunk of data in,
>> then operates on it. I'm guessing that the code after the following
>> line expects that there isn't any data left over from previous runs
>> through the loop.
>>
> the rational for this being ok is thta the copy operation into block is:
>                 ret = wlcore_read_hwaddr(wl, addr, block,
>                                         wl->fw_mem_block_size, false);
>
> this will end up in the .read methods where block should be completely
> overwritten (length == full block size), so within the loop if successful
> this should be correct - if not successful it would "goto out" witout
> using the content of block.
>
> Am I overlooking something here ?

It's quite possible I am. I didn't look at the implementation of
wlcore_read_hwaddr() so I'm only guessing that it could do partial
reads.

That said, if it does overwrite the entire buffer each time, then
there's no need to use kzalloc() to allocate the buffer in the first
place.

Either way, it needs a review from someone more familiar with the code.

Thanks,

-- 
Julian Calaby

Email: julian.calaby@gmail.com
Profile: http://www.google.com/profiles/julian.calaby/