2 files changed, 25 insertions, 0 deletions

diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking
index e0cce2a5f820..2db1900d7538 100644
--- a/Documentation/filesystems/Locking
+++ b/Documentation/filesystems/Locking
@@ -206,6 +206,8 @@ prototypes:
         int (*launder_page)(struct page *);
         int (*is_partially_uptodate)(struct page *, read_descriptor_t *, unsigned long);
         int (*error_remove_page)(struct address_space *, struct page *);
+        int (*swap_activate)(struct file *);
+        int (*swap_deactivate)(struct file *);
 
 locking rules:
         All except set_page_dirty and freepage may block
@@ -229,6 +231,8 @@ migratepage:		yes (both)
 launder_page:           yes
 is_partially_uptodate:  yes
 error_remove_page:      yes
+swap_activate:          no
+swap_deactivate:        no
 
         ->write_begin(), ->write_end(), ->sync_page() and ->readpage()
 may be called from the request handler (/dev/loop).
@@ -330,6 +334,15 @@ cleaned, or an error value if not. Note that in order to prevent the page
 getting mapped back in and redirtied, it needs to be kept locked
 across the entire operation.
 
+        ->swap_activate will be called with a non-zero argument on
+files backing (non block device backed) swapfiles. A return value
+of zero indicates success, in which case this file can be used for
+backing swapspace. The swapspace operations will be proxied to the
+address space operations.
+
+        ->swap_deactivate() will be called in the sys_swapoff()
+path after ->swap_activate() returned success.
+
 ----------------------- file_lock_operations ------------------------------
 prototypes:
         void (*fl_copy_lock)(struct file_lock *, struct file_lock *);
diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt
index aa754e01464e..065aa2dc0835 100644
--- a/Documentation/filesystems/vfs.txt
+++ b/Documentation/filesystems/vfs.txt
@@ -592,6 +592,8 @@ struct address_space_operations {
         int (*migratepage) (struct page *, struct page *);
         int (*launder_page) (struct page *);
         int (*error_remove_page) (struct mapping *mapping, struct page *page);
+        int (*swap_activate)(struct file *);
+        int (*swap_deactivate)(struct file *);
 };
 
   writepage: called by the VM to write a dirty page to backing store.
@@ -760,6 +762,16 @@ struct address_space_operations {
         Setting this implies you deal with pages going away under you,
         unless you have them locked or reference counts increased.
 
+  swap_activate: Called when swapon is used on a file to allocate
+        space if necessary and pin the block lookup information in
+        memory. A return value of zero indicates success,
+        in which case this file can be used to back swapspace. The
+        swapspace operations will be proxied to this address space's
+        ->swap_{out,in} methods.
+
+  swap_deactivate: Called during swapoff on files where swap_activate
+        was successful.
+
 
 The File Object
 ===============