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SubjectRe: [PATCH] ARM-SMMU: Delete error messages for a failed memory allocation in three functions
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On 20/01/18 14:36, SF Markus Elfring wrote:
> From: Markus Elfring <elfring@users.sourceforge.net>
> Date: Sat, 20 Jan 2018 15:30:17 +0100
>
> Omit extra messages for a memory allocation failure in these functions.

Why?

It's your job as patch author to convince reviewers and maintainers why
your change is a good thing and they should spend their time looking at
it, much less consider merging it. This may as well be "delete some
stuff because I feel like it".

Do bear in mind the nature of these drivers; Arm SMMUs are not something
you find in microcontrollers. On systems using these drivers, it will
make no difference whatsoever to anyone if the many-megabyte kernel
image is 47 bytes (or whatever) smaller.

> This issue was detected by using the Coccinelle software.

I think I'm going to have to start treating mention of Coccinelle as a
potential disclaimer saying "I haven't attempted to understand the code
I'm changing" :(

> Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
> ---
> drivers/iommu/arm-smmu-v3.c | 9 +++------
> drivers/iommu/arm-smmu.c | 9 +++------
> 2 files changed, 6 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
> index f122071688fd..5c2a7103d494 100644
> --- a/drivers/iommu/arm-smmu-v3.c
> +++ b/drivers/iommu/arm-smmu-v3.c
> @@ -2134,10 +2134,8 @@ static int arm_smmu_init_l1_strtab(struct arm_smmu_device *smmu)
> void *strtab = smmu->strtab_cfg.strtab;
>
> cfg->l1_desc = devm_kzalloc(smmu->dev, size, GFP_KERNEL);
> - if (!cfg->l1_desc) {
> - dev_err(smmu->dev, "failed to allocate l1 stream table desc\n");

OK, I'll stop playing *completely* dumb; I do know you would get a splat
if kmalloc() ever did fail. But what you're removing isn't
printk("failed to allocate memory\n"), it's a message which says exactly
what allocation failed *for which device*. Can you clarify how I'm going
to diagnose this particular problem from the generic splat when all I
have is en email from a customer with a dmesg dump?

> + if (!cfg->l1_desc)
> return -ENOMEM;
> - }
>
> for (i = 0; i < cfg->num_l1_ents; ++i) {
> arm_smmu_write_strtab_l1_desc(strtab, &cfg->l1_desc[i]);
> @@ -2828,10 +2826,9 @@ static int arm_smmu_device_probe(struct platform_device *pdev)
> bool bypass;
>
> smmu = devm_kzalloc(dev, sizeof(*smmu), GFP_KERNEL);
> - if (!smmu) {
> - dev_err(dev, "failed to allocate arm_smmu_device\n");
> + if (!smmu)
> return -ENOMEM;
> - }
> +
> smmu->dev = dev;
>
> if (dev->of_node) {
> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
> index 78d4c6b8f1ba..a4da4a870a2e 100644
> --- a/drivers/iommu/arm-smmu.c
> +++ b/drivers/iommu/arm-smmu.c
> @@ -2048,10 +2048,9 @@ static int arm_smmu_device_probe(struct platform_device *pdev)
> int num_irqs, i, err;
>
> smmu = devm_kzalloc(dev, sizeof(*smmu), GFP_KERNEL);
> - if (!smmu) {
> - dev_err(dev, "failed to allocate arm_smmu_device\n");
> + if (!smmu)
> return -ENOMEM;
> - }
> +
> smmu->dev = dev;
>
> if (dev->of_node)
> @@ -2084,10 +2083,8 @@ static int arm_smmu_device_probe(struct platform_device *pdev)
>
> smmu->irqs = devm_kzalloc(dev, sizeof(*smmu->irqs) * num_irqs,
> GFP_KERNEL);
> - if (!smmu->irqs) {
> - dev_err(dev, "failed to allocate %d irqs\n", num_irqs);

This more than any other is removing potentially useful information:
"failed to allocate 37890756 irqs", for instance, would indicate a bug
which is very much *not* an out-of-memory condition.

Robin.

> + if (!smmu->irqs)
> return -ENOMEM;
> - }
>
> for (i = 0; i < num_irqs; ++i) {
> int irq = platform_get_irq(pdev, i);
>

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