Re: missing clear bdr in check_ram_in_range_map()?
From: Christoph Hellwig
Date: Thu Dec 12 2024 - 02:14:30 EST
On Mon, Dec 09, 2024 at 06:50:06PM +0800, Baochen Qiang wrote:
> Hi,
>
> while checking check_ram_in_range_map() I am confused by the condition set/check on bdr.
> If I am reading the code correctly, if bdr is set once, it would never get cleared, hence
> that function will always returns 0.
>
> should we clear bdr before each new iteration?
I think so. Even better refactor the code so that the non-NULL bdr
doesn't leak out:
diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 5b4e6d3bf7bc..181e244f410a 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -584,6 +584,22 @@ int dma_direct_supported(struct device *dev, u64 mask)
return mask >= phys_to_dma_unencrypted(dev, min_mask);
}
+static const struct bus_dma_region *dma_find_range(struct device *dev,
+ unsigned long start_pfn)
+{
+ const struct bus_dma_region *m;
+
+ for (m = dev->dma_range_map; PFN_DOWN(m->size); m++) {
+ unsigned long cpu_start_pfn = PFN_DOWN(m->cpu_start);
+
+ if (start_pfn >= cpu_start_pfn &&
+ start_pfn - cpu_start_pfn < PFN_DOWN(m->size))
+ return m;
+ }
+
+ return NULL;
+}
+
/*
* To check whether all ram resource ranges are covered by dma range map
* Returns 0 when further check is needed
@@ -593,23 +609,14 @@ static int check_ram_in_range_map(unsigned long start_pfn,
unsigned long nr_pages, void *data)
{
unsigned long end_pfn = start_pfn + nr_pages;
- const struct bus_dma_region *bdr = NULL;
- const struct bus_dma_region *m;
struct device *dev = data;
while (start_pfn < end_pfn) {
- for (m = dev->dma_range_map; PFN_DOWN(m->size); m++) {
- unsigned long cpu_start_pfn = PFN_DOWN(m->cpu_start);
+ const struct bus_dma_region *bdr;
- if (start_pfn >= cpu_start_pfn &&
- start_pfn - cpu_start_pfn < PFN_DOWN(m->size)) {
- bdr = m;
- break;
- }
- }
+ bdr = dma_find_range(dev, start_pfn);
if (!bdr)
return 1;
-
start_pfn = PFN_DOWN(bdr->cpu_start) + PFN_DOWN(bdr->size);
}