[PATCH] mm: memory: Introduce new vmf_insert_mixed_mkwrite

[Souptick Joarder <jrdr.linux@gmail.com>]

vm_insert_mixed_mkwrite() has inefficiency when it
returns err, driver has to convert err to vm_fault_t
type. With new vmf_insert_mixed_mkwrite we can handle
this limitation.

As of now vm_insert_mixed_mkwrite() is only getting
invoked from fs/dax.c, so this change has to go first
in linus tree before changes in dax.

Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
---
 include/linux/mm.h |  4 ++--
 mm/memory.c        | 15 +++++++++++----
 2 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 1ac1f06..9fe441c 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2423,8 +2423,8 @@ int vm_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
 			unsigned long pfn, pgprot_t pgprot);
 int vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
 			pfn_t pfn);
-int vm_insert_mixed_mkwrite(struct vm_area_struct *vma, unsigned long addr,
-			pfn_t pfn);
+vm_fault_t vmf_insert_mixed_mkwrite(struct vm_area_struct *vma,
+		unsigned long addr, pfn_t pfn);
 int vm_iomap_memory(struct vm_area_struct *vma, phys_addr_t start, unsigned long len);
 
 static inline vm_fault_t vmf_insert_page(struct vm_area_struct *vma,
diff --git a/mm/memory.c b/mm/memory.c
index 01f5464..721cfd5 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1955,12 +1955,19 @@ int vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
 }
 EXPORT_SYMBOL(vm_insert_mixed);
 
-int vm_insert_mixed_mkwrite(struct vm_area_struct *vma, unsigned long addr,
-			pfn_t pfn)
+vm_fault_t vmf_insert_mixed_mkwrite(struct vm_area_struct *vma,
+		unsigned long addr, pfn_t pfn)
 {
-	return __vm_insert_mixed(vma, addr, pfn, true);
+	int err;
+
+	err =  __vm_insert_mixed(vma, addr, pfn, true);
+	if (err == -ENOMEM)
+		return VM_FAULT_OOM;
+	if (err < 0 && err != -EBUSY)
+		return VM_FAULT_SIGBUS;
+	return VM_FAULT_NOPAGE;
 }
-EXPORT_SYMBOL(vm_insert_mixed_mkwrite);
+EXPORT_SYMBOL(vmf_insert_mixed_mkwrite);
 
 /*
  * maps a range of physical memory into the requested pages. the old
-- 
1.9.1