Re: [PATCH 1/5] ISDN-Gigaset: Use kmalloc_array() in two functions
On Wed, 2016-09-28 at 18:38 +0200, SF Markus Elfring wrote: > > I'm not going to change code just because some checker suggests to > > do so. > > The script "checkpatch.pl" can point information out like the > following. > > WARNING: Prefer kmalloc_array over kmalloc with multiply Am I being trolled? Paul Bolle
Re: [PATCH 1/5] ISDN-Gigaset: Use kmalloc_array() in two functions
>> * Multiplications for the size determination of memory allocations >> indicated that array data structures should be processed. >> Thus use the corresponding function "kmalloc_array". > > Was the current code incorrect? I suggest to use a safer interface for array allocations. > What makes kmalloc_array() better? 1. How do you think about the safety checks that this function provides? 2. Will you be also affected by further software evolution here? 2016-07-26 mm: faster kmalloc_array(), kcalloc() https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/commit/?id=91c6a05f72a996bee5133e76374ab3ad7d3b9b72 > I'm not going to change code just because some checker suggests to do so. The script "checkpatch.pl" can point information out like the following. WARNING: Prefer kmalloc_array over kmalloc with multiply >> This issue was detected by using the Coccinelle software. > > So? And which coccinelle script was actually used? How do you think about to look into related information sources? https://github.com/coccinelle/coccinelle/issues/81 Would you like to experiment any further with an excerpt? @replacement1@ expression count, target; type T; @@ target = - kmalloc(sizeof(T) * (count) + kmalloc_array(count, sizeof(T) , ...); @replacement2@ expression count, pointer, target; @@ target = - kmalloc(sizeof(*pointer) * (count) + kmalloc_array(count, sizeof(*pointer) , ...); > I couldn't spot a coccinelle script doing that in the current tree. This is true for such a software update opportunity. >> * Replace the specification of a data structure by a pointer dereference >> to make the corresponding size determination a bit safer according to >> the Linux coding style convention. > > I'm not happy with you mixing this with the above, less trivial, change. I find that it is a useful combination. - A parameter is adjusted together with a special function name. >> -drv->cs = kmalloc(minors * sizeof *drv->cs, GFP_KERNEL); >> +drv->cs = kmalloc_array(minors, sizeof(*drv->cs), GFP_KERNEL); > > For "minors" the same holds as for "channels", above. > > And you snuck in a parentheses change. That should have probably been > merged with 5/5. Would you prefer to add them in another update step? Regards, Markus
Re: [PATCH 1/5] ISDN-Gigaset: Use kmalloc_array() in two functions
On Mon, 2016-09-26 at 17:38 +0200, SF Markus Elfring wrote:
> * Multiplications for the size determination of memory allocations
> indicated that array data structures should be processed.
> Thus use the corresponding function "kmalloc_array".
Was the current code incorrect? What makes kmalloc_array() better? None
of this is obvious to me.
I'm not going to change code just because some checker suggests to do
so.
> This issue was detected by using the Coccinelle software.
So? And which coccinelle script was actually used? I couldn't spot a
coccinelle script doing that in the current tree.
> * Replace the specification of a data structure by a pointer dereference
> to make the corresponding size determination a bit safer according to
> the Linux coding style convention.
I'm not happy with you mixing this with the above, less trivial,
change.
> Signed-off-by: Markus Elfring
> --- a/drivers/isdn/gigaset/common.c
> +++ b/drivers/isdn/gigaset/common.c
> @@ -709,8 +709,7 @@ struct cardstate *gigaset_initcs(struct gigaset_driver
> *drv, int channels,
>
> cs->mode = M_UNKNOWN;
> cs->mstate = MS_UNINITIALIZED;
> -
Unrelated whitespace change.
> - cs->bcs = kmalloc(channels * sizeof(struct bc_state), GFP_KERNEL);
> + cs->bcs = kmalloc_array(channels, sizeof(*cs->bcs), GFP_KERNEL);
For the record: "channels" is basically hardcoded in the three gigaset
hardware drivers.
> cs->inbuf = kmalloc(sizeof(struct inbuf_t), GFP_KERNEL);
> if (!cs->bcs || !cs->inbuf) {
> pr_err("out of memory\n");
> @@ -1089,8 +1088,7 @@ struct gigaset_driver
> *gigaset_initdriver(unsigned minor, unsigned minors,
> drv->ops = ops;
> drv->owner = owner;
> INIT_LIST_HEAD(&drv->list);
> -
Again unrelated whitespace change.
> - drv->cs = kmalloc(minors * sizeof *drv->cs, GFP_KERNEL);
> + drv->cs = kmalloc_array(minors, sizeof(*drv->cs), GFP_KERNEL);
For "minors" the same holds as for "channels", above.
And you snuck in a parentheses change. That should have probably been
merged with 5/5.
> if (!drv->cs)
> goto error;
Paul Bolle
[PATCH 1/5] ISDN-Gigaset: Use kmalloc_array() in two functions
From: Markus Elfring
Date: Sun, 25 Sep 2016 22:22:04 +0200
* Multiplications for the size determination of memory allocations
indicated that array data structures should be processed.
Thus use the corresponding function "kmalloc_array".
This issue was detected by using the Coccinelle software.
* Replace the specification of a data structure by a pointer dereference
to make the corresponding size determination a bit safer according to
the Linux coding style convention.
Signed-off-by: Markus Elfring
---
drivers/isdn/gigaset/common.c | 6 ++
1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/drivers/isdn/gigaset/common.c b/drivers/isdn/gigaset/common.c
index 7c78144..cecbb6a 100644
--- a/drivers/isdn/gigaset/common.c
+++ b/drivers/isdn/gigaset/common.c
@@ -709,8 +709,7 @@ struct cardstate *gigaset_initcs(struct gigaset_driver
*drv, int channels,
cs->mode = M_UNKNOWN;
cs->mstate = MS_UNINITIALIZED;
-
- cs->bcs = kmalloc(channels * sizeof(struct bc_state), GFP_KERNEL);
+ cs->bcs = kmalloc_array(channels, sizeof(*cs->bcs), GFP_KERNEL);
cs->inbuf = kmalloc(sizeof(struct inbuf_t), GFP_KERNEL);
if (!cs->bcs || !cs->inbuf) {
pr_err("out of memory\n");
@@ -1089,8 +1088,7 @@ struct gigaset_driver *gigaset_initdriver(unsigned minor,
unsigned minors,
drv->ops = ops;
drv->owner = owner;
INIT_LIST_HEAD(&drv->list);
-
- drv->cs = kmalloc(minors * sizeof *drv->cs, GFP_KERNEL);
+ drv->cs = kmalloc_array(minors, sizeof(*drv->cs), GFP_KERNEL);
if (!drv->cs)
goto error;
--
2.10.0
