mm: add support for a filesystem to activate swap files and use direct_IO for writing...

[linux-2.6-block.git] / Documentation / filesystems / Locking

diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking
index e0cce2a5f820a6327f9ea1558717434c490e8aae..2db1900d7538eb5f8c02acc15391556f29357ab2 100644 (file)
--- 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 *);