powerpc/mm/dax: Fix the condition when checking if altmap vmemap can cross-boundary

Without this fix, the last subsection vmemmap can end up in memory even if
the namespace is created with -M mem and has sufficient space in the altmap
area.

Fixes: cf387d9644d8 ("libnvdimm/altmap: Track namespace boundaries in altmap")
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Tested-by: Sachin Sant <sachinp@linux.ibm.com <mailto:sachinp@linux.ibm.com>>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230616110826.344417-6-aneesh.kumar@linux.ibm.com

diff --git a/arch/powerpc/mm/init_64.c b/arch/powerpc/mm/init_64.c
index 05b0d58..fe1b830 100644 (file)
--- a/arch/powerpc/mm/init_64.c
+++ b/arch/powerpc/mm/init_64.c
@@ -189,7 +189,7 @@ static bool altmap_cross_boundary(struct vmem_altmap *altmap, unsigned long star
        unsigned long nr_pfn = page_size / sizeof(struct page);
        unsigned long start_pfn = page_to_pfn((struct page *)start);
 
-       if ((start_pfn + nr_pfn) > altmap->end_pfn)
+       if ((start_pfn + nr_pfn - 1) > altmap->end_pfn)
                return true;
 
        if (start_pfn < altmap->base_pfn)