[PATCH v3 08/12] book3s64/hash: Disable debug_pagealloc if it requires more memory

[Ritesh Harjani (IBM)]

Make size of the linear map to be allocated in RMA region to be of
ppc64_rma_size / 4. If debug_pagealloc requires more memory than that
then do not allocate any memory and disable debug_pagealloc.

Signed-off-by: Ritesh Harjani (IBM) <ritesh.l...@gmail.com>
---
 arch/powerpc/mm/book3s64/hash_utils.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/mm/book3s64/hash_utils.c 
b/arch/powerpc/mm/book3s64/hash_utils.c
index 11975a2f7403..f51f2cd9bf22 100644
--- a/arch/powerpc/mm/book3s64/hash_utils.c
+++ b/arch/powerpc/mm/book3s64/hash_utils.c
@@ -331,9 +331,19 @@ static unsigned long linear_map_hash_count;
 static DEFINE_RAW_SPINLOCK(linear_map_hash_lock);
 static inline void hash_debug_pagealloc_alloc_slots(void)
 {
+       unsigned long max_hash_count = ppc64_rma_size / 4;
+
        if (!debug_pagealloc_enabled())
                return;
        linear_map_hash_count = memblock_end_of_DRAM() >> PAGE_SHIFT;
+       if (unlikely(linear_map_hash_count > max_hash_count)) {
+               pr_info("linear map size (%llu) greater than 4 times RMA region 
(%llu). Disabling debug_pagealloc\n",
+                       ((u64)linear_map_hash_count << PAGE_SHIFT),
+                       ppc64_rma_size);
+               linear_map_hash_count = 0;
+               return;
+       }
+
        linear_map_hash_slots = memblock_alloc_try_nid(
                        linear_map_hash_count, 1, MEMBLOCK_LOW_LIMIT,
                        ppc64_rma_size, NUMA_NO_NODE);
@@ -344,7 +354,7 @@ static inline void hash_debug_pagealloc_alloc_slots(void)
 
 static inline void hash_debug_pagealloc_add_slot(phys_addr_t paddr, int slot)
 {
-       if (!debug_pagealloc_enabled())
+       if (!debug_pagealloc_enabled() || !linear_map_hash_count)
                return;
        if ((paddr >> PAGE_SHIFT) < linear_map_hash_count)
                linear_map_hash_slots[paddr >> PAGE_SHIFT] = slot | 0x80;
@@ -356,6 +366,9 @@ static int hash_debug_pagealloc_map_pages(struct page 
*page, int numpages,
        unsigned long flags, vaddr, lmi;
        int i;
 
+       if (!debug_pagealloc_enabled() || !linear_map_hash_count)
+               return 0;
+
        local_irq_save(flags);
        for (i = 0; i < numpages; i++, page++) {
                vaddr = (unsigned long)page_address(page);
-- 
2.46.0