dma-mapping: fix missing clear bdr in check_ram_in_range_map()

As discussed in [1], if 'bdr' is set once, it would never get
cleared, hence 0 is always returned.

Refactor the range check hunk into a new helper dma_find_range(),
which allows 'bdr' to be cleared in each iteration.

Link: https://lore.kernel.org/all/64931fac-085b-4ff3-9314-84bac2fa9bdb@quicinc.com/
Fixes: a409d9600959 ("dma-mapping: fix dma_addressing_limited() if dma_range_map can't cover all system RAM")
Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Baochen Qiang <quic_bqiang@quicinc.com>
Link: https://lore.kernel.org/r/20250307030350.69144-1-quic_bqiang@quicinc.com
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>

diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 5b4e6d3bf7bcca8930877ba078aed4ce26828f06..b8fe0b3d0ffb69a17a8860c6d92a8e0c15a727fb 100644 (file)
--- 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
@@ -593,20 +609,12 @@ 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;