mm: fix cache mode of dax pmd mappings

track_pfn_insert() in vmf_insert_pfn_pmd() is marking dax mappings as
uncacheable rendering them impractical for application usage.  DAX-pte
mappings are cached and the goal of establishing DAX-pmd mappings is to
attain more performance, not dramatically less (3 orders of magnitude).

track_pfn_insert() relies on a previous call to reserve_memtype() to
establish the expected page_cache_mode for the range.  While memremap()
arranges for reserve_memtype() to be called, devm_memremap_pages() does
not.  So, teach track_pfn_insert() and untrack_pfn() how to handle
tracking without a vma, and arrange for devm_memremap_pages() to
establish the write-back-cache reservation in the memtype tree.

Cc: <stable@vger.kernel.org>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Nilesh Choudhury <nilesh.choudhury@oracle.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reported-by: Toshi Kani <toshi.kani@hpe.com>
Reported-by: Kai Zhang <kai.ka.zhang@oracle.com>
Acked-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index ecb1b69c1651323ea412914c1701712ea77d41ca..170cc4ff057b398382bef3dd635d6a9115460d88 100644 (file)
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -927,9 +927,10 @@ int track_pfn_copy(struct vm_area_struct *vma)
 }
 
 /*
- * prot is passed in as a parameter for the new mapping. If the vma has a
- * linear pfn mapping for the entire range reserve the entire vma range with
- * single reserve_pfn_range call.
+ * prot is passed in as a parameter for the new mapping. If the vma has
+ * a linear pfn mapping for the entire range, or no vma is provided,
+ * reserve the entire pfn + size range with single reserve_pfn_range
+ * call.
  */
 int track_pfn_remap(struct vm_area_struct *vma, pgprot_t *prot,
                    unsigned long pfn, unsigned long addr, unsigned long size)
@@ -938,11 +939,12 @@ int track_pfn_remap(struct vm_area_struct *vma, pgprot_t *prot,
        enum page_cache_mode pcm;
 
        /* reserve the whole chunk starting from paddr */
-       if (addr == vma->vm_start && size == (vma->vm_end - vma->vm_start)) {
+       if (!vma || (addr == vma->vm_start
+                               && size == (vma->vm_end - vma->vm_start))) {
                int ret;
 
                ret = reserve_pfn_range(paddr, size, prot, 0);
-               if (!ret)
+               if (ret == 0 && vma)
                        vma->vm_flags |= VM_PAT;
                return ret;
        }
@@ -997,7 +999,7 @@ void untrack_pfn(struct vm_area_struct *vma, unsigned long pfn,
        resource_size_t paddr;
        unsigned long prot;
 
-       if (!(vma->vm_flags & VM_PAT))
+       if (vma && !(vma->vm_flags & VM_PAT))
                return;
 
        /* free the chunk starting from pfn or the whole chunk */
@@ -1011,7 +1013,8 @@ void untrack_pfn(struct vm_area_struct *vma, unsigned long pfn,
                size = vma->vm_end - vma->vm_start;
        }
        free_pfn_range(paddr, size);
-       vma->vm_flags &= ~VM_PAT;
+       if (vma)
+               vma->vm_flags &= ~VM_PAT;
 }
 
 /*

diff --git a/kernel/memremap.c b/kernel/memremap.c
index 251d16b4cb41e67111ff2f1f783bf39cdea13822..b501e390bb34403c11d6ae09c31ea9fcb769ea8e 100644 (file)
--- a/kernel/memremap.c
+++ b/kernel/memremap.c
@@ -247,6 +247,7 @@ static void devm_memremap_pages_release(struct device *dev, void *data)
        align_start = res->start & ~(SECTION_SIZE - 1);
        align_size = ALIGN(resource_size(res), SECTION_SIZE);
        arch_remove_memory(align_start, align_size);
+       untrack_pfn(NULL, PHYS_PFN(align_start), align_size);
        pgmap_radix_release(res);
        dev_WARN_ONCE(dev, pgmap->altmap && pgmap->altmap->alloc,
                        "%s: failed to free all reserved pages\n", __func__);
@@ -282,6 +283,7 @@ void *devm_memremap_pages(struct device *dev, struct resource *res,
                struct percpu_ref *ref, struct vmem_altmap *altmap)
 {
        resource_size_t key, align_start, align_size, align_end;
+       pgprot_t pgprot = PAGE_KERNEL;
        struct dev_pagemap *pgmap;
        struct page_map *page_map;
        int error, nid, is_ram;
@@ -351,6 +353,11 @@ void *devm_memremap_pages(struct device *dev, struct resource *res,
        if (nid < 0)
                nid = numa_mem_id();
 
+       error = track_pfn_remap(NULL, &pgprot, PHYS_PFN(align_start), 0,
+                       align_size);
+       if (error)
+               goto err_pfn_remap;
+
        error = arch_add_memory(nid, align_start, align_size, true);
        if (error)
                goto err_add_memory;
@@ -371,6 +378,8 @@ void *devm_memremap_pages(struct device *dev, struct resource *res,
        return __va(res->start);
 
  err_add_memory:
+       untrack_pfn(NULL, PHYS_PFN(align_start), align_size);
+ err_pfn_remap:
  err_radix:
        pgmap_radix_release(res);
        devres_free(page_map);