lkml.org 
[lkml]   [2019]   [Feb]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH v1 4/7] iommu/vt-d: Remove unnecessary local variable initializations
On Sun, Feb 10, 2019 at 8:00 PM Lu Baolu <baolu.lu@linux.intel.com> wrote:
>
> Hi,
>
> On 2/9/19 6:06 AM, Bjorn Helgaas wrote:
> > From: Bjorn Helgaas <bhelgaas@google.com>
> >
> > A local variable initialization is a hint that the variable will be used in
> > an unusual way. If the initialization is unnecessary, that hint becomes a
> > distraction.
> >
> > Remove unnecessary initializations. No functional change intended.
> >
> > Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
> > ---
> > drivers/iommu/intel-iommu.c | 27 +++++++++++++--------------
> > 1 file changed, 13 insertions(+), 14 deletions(-)
> >
> > diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> > index 81077803880f..2acd08c82cdc 100644
> > --- a/drivers/iommu/intel-iommu.c
> > +++ b/drivers/iommu/intel-iommu.c
> > @@ -865,7 +865,7 @@ static void free_context_table(struct intel_iommu *iommu)
> > static struct dma_pte *pfn_to_dma_pte(struct dmar_domain *domain,
> > unsigned long pfn, int *target_level)
> > {
> > - struct dma_pte *parent, *pte = NULL;
> > + struct dma_pte *parent, *pte;
> > int level = agaw_to_level(domain->agaw);
> > int offset;
> >
> > @@ -922,7 +922,7 @@ static struct dma_pte *dma_pfn_level_pte(struct dmar_domain *domain,
> > unsigned long pfn,
> > int level, int *large_page)
> > {
> > - struct dma_pte *parent, *pte = NULL;
> > + struct dma_pte *parent, *pte;
> > int total = agaw_to_level(domain->agaw);
> > int offset;
> >
> > @@ -954,7 +954,7 @@ static void dma_pte_clear_range(struct dmar_domain *domain,
> > unsigned long start_pfn,
> > unsigned long last_pfn)
> > {
> > - unsigned int large_page = 1;
> > + unsigned int large_page;
> > struct dma_pte *first_pte, *pte;
> >
> > BUG_ON(!domain_pfn_supported(domain, start_pfn));
> > @@ -1132,7 +1132,7 @@ static struct page *domain_unmap(struct dmar_domain *domain,
> > unsigned long start_pfn,
> > unsigned long last_pfn)
> > {
> > - struct page *freelist = NULL;
> > + struct page *freelist;
>
> I am afraid this change might cause problem. "freelist" might go through
> dma_pte_clear_level() without any touches.

Thanks for your review! Can you clarify your concern? "freelist"
isn't passed into dma_pte_clear_level(). Here's the existing code
(before this patch). I don't see a use of "freelist" before we assign
the result of dma_pte_clear_level() to it. But maybe I'm overlooking
something.

static struct page *domain_unmap(struct dmar_domain *domain,
unsigned long start_pfn,
unsigned long last_pfn)
{
struct page *freelist = NULL;

BUG_ON(!domain_pfn_supported(domain, start_pfn));
BUG_ON(!domain_pfn_supported(domain, last_pfn));
BUG_ON(start_pfn > last_pfn);

/* we don't need lock here; nobody else touches the iova range */
freelist = dma_pte_clear_level(domain, agaw_to_level(domain->agaw),
domain->pgd, 0, start_pfn,
last_pfn, NULL);

\
 
 \ /
  Last update: 2019-02-11 04:33    [W:0.046 / U:2.484 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site