1 files changed, 8 insertions, 0 deletions

diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking
index c3cd6279e92e..7c3f187d48bf 100644
--- a/Documentation/filesystems/Locking
+++ b/Documentation/filesystems/Locking
@@ -523,6 +523,7 @@ prototypes:
         void (*close)(struct vm_area_struct*);
         int (*fault)(struct vm_area_struct*, struct vm_fault *);
         int (*page_mkwrite)(struct vm_area_struct *, struct vm_fault *);
+        int (*pfn_mkwrite)(struct vm_area_struct *, struct vm_fault *);
         int (*access)(struct vm_area_struct *, unsigned long, void*, int, int);
 
 locking rules:
@@ -532,6 +533,7 @@ close:		yes
 fault:          yes             can return with page locked
 map_pages:      yes
 page_mkwrite:   yes             can return with page locked
+pfn_mkwrite:    yes
 access:         yes
 
         ->fault() is called when a previously not present pte is about
@@ -558,6 +560,12 @@ the page has been truncated, the filesystem should not look up a new page
 like the ->fault() handler, but simply return with VM_FAULT_NOPAGE, which
 will cause the VM to retry the fault.
 
+        ->pfn_mkwrite() is the same as page_mkwrite but when the pte is
+VM_PFNMAP or VM_MIXEDMAP with a page-less entry. Expected return is
+VM_FAULT_NOPAGE. Or one of the VM_FAULT_ERROR types. The default behavior
+after this call is to make the pte read-write, unless pfn_mkwrite returns
+an error.
+
         ->access() is called when get_user_pages() fails in
 access_process_vm(), typically used to debug a process through
 /proc/pid/mem or ptrace.  This function is needed only for