Re: Regression after commit 19809c2da28a ("mm, vmalloc: use __GFP_HIGHMEM implicitly")

[Matthew Wilcox]

On Thu, Feb 08, 2018 at 03:20:04PM -0800, Matthew Wilcox wrote:
> So ... we could enable ZONE_DMA32 on 32-bit architectures.  I don't know
> what side-effects that might have; it's clearly only been tested on 64-bit
> architectures so far.
> 
> It might be best to just revert 19809c2da28a and the follow-on 704b862f9efd.

Alternatively, try this.  It passes in GFP_DMA32 from vmalloc_32,
regardless of whether ZONE_DMA32 exists or not.  If ZONE_DMA32 doesn't
exist, then we clear it in __vmalloc_area_node(), after using it to
determine that we shouldn't set __GFP_HIGHMEM.

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 673942094328..91e8a95123c4 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1669,10 +1669,11 @@ static void *__vmalloc_area_node(struct vm_struct 
*area, gfp_t gfp_mask,
        struct page **pages;
        unsigned int nr_pages, array_size, i;
        const gfp_t nested_gfp = (gfp_mask & GFP_RECLAIM_MASK) | __GFP_ZERO;
-       const gfp_t alloc_mask = gfp_mask | __GFP_NOWARN;
-       const gfp_t highmem_mask = (gfp_mask & (GFP_DMA | GFP_DMA32)) ?
-                                       0 :
-                                       __GFP_HIGHMEM;
+       gfp_t alloc_mask = gfp_mask | __GFP_NOWARN;
+       if (!(alloc_mask & GFP_ZONEMASK))
+               alloc_mask |= __GFP_HIGHMEM;
+       if (!IS_ENABLED(CONFIG_ZONE_DMA32) && (alloc_mask & __GFP_DMA32))
+               alloc_mask &= ~__GFP_DMA32;
 
        nr_pages = get_vm_area_size(area) >> PAGE_SHIFT;
        array_size = (nr_pages * sizeof(struct page *));
@@ -1680,7 +1681,7 @@ static void *__vmalloc_area_node(struct vm_struct *area, 
gfp_t gfp_mask,
        area->nr_pages = nr_pages;
        /* Please note that the recursion is strictly bounded. */
        if (array_size > PAGE_SIZE) {
-               pages = __vmalloc_node(array_size, 1, nested_gfp|highmem_mask,
+               pages = __vmalloc_node(array_size, 1, nested_gfp|__GFP_HIGHMEM,
                                PAGE_KERNEL, node, area->caller);
        } else {
                pages = kmalloc_node(array_size, nested_gfp, node);
@@ -1696,9 +1697,9 @@ static void *__vmalloc_area_node(struct vm_struct *area, 
gfp_t gfp_mask,
                struct page *page;
 
                if (node == NUMA_NO_NODE)
-                       page = alloc_page(alloc_mask|highmem_mask);
+                       page = alloc_page(alloc_mask);
                else
-                       page = alloc_pages_node(node, alloc_mask|highmem_mask, 
0);
+                       page = alloc_pages_node(node, alloc_mask, 0);
 
                if (unlikely(!page)) {
                        /* Successfully allocated i pages, free them in 
__vunmap() */
@@ -1706,7 +1707,7 @@ static void *__vmalloc_area_node(struct vm_struct *area, 
gfp_t gfp_mask,
                        goto fail;
                }
                area->pages[i] = page;
-               if (gfpflags_allow_blocking(gfp_mask|highmem_mask))
+               if (gfpflags_allow_blocking(gfp_mask))
                        cond_resched();
        }
 
@@ -1942,12 +1943,10 @@ void *vmalloc_exec(unsigned long size)
                              NUMA_NO_NODE, __builtin_return_address(0));
 }
 
-#if defined(CONFIG_64BIT) && defined(CONFIG_ZONE_DMA32)
-#define GFP_VMALLOC32 GFP_DMA32 | GFP_KERNEL
-#elif defined(CONFIG_64BIT) && defined(CONFIG_ZONE_DMA)
+#if defined(CONFIG_64BIT) && !defined(CONFIG_ZONE_DMA32)
 #define GFP_VMALLOC32 GFP_DMA | GFP_KERNEL
 #else
-#define GFP_VMALLOC32 GFP_KERNEL
+#define GFP_VMALLOC32 GFP_DMA32 | GFP_KERNEL
 #endif
 
 /**