Merge ../linux-2.6-watchdog-mm

[pandora-kernel.git] / Documentation / filesystems / Locking

diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking
index 790ef6f..28bfea7 100644 (file)
--- a/Documentation/filesystems/Locking
+++ b/Documentation/filesystems/Locking
@@ -171,6 +171,7 @@ prototypes:
        int (*releasepage) (struct page *, int);
        int (*direct_IO)(int, struct kiocb *, const struct iovec *iov,
                        loff_t offset, unsigned long nr_segs);
+       int (*launder_page) (struct page *);
 
 locking rules:
        All except set_page_dirty may block
@@ -188,6 +189,7 @@ bmap:                       yes
 invalidatepage:                no      yes
 releasepage:           no      yes
 direct_IO:             no
+launder_page:          no      yes
 
        ->prepare_write(), ->commit_write(), ->sync_page() and ->readpage()
 may be called from the request handler (/dev/loop).
@@ -281,6 +283,12 @@ buffers from the page in preparation for freeing it.  It returns zero to
 indicate that the buffers are (or may be) freeable.  If ->releasepage is zero,
 the kernel assumes that the fs has no private interest in the buffers.
 
+       ->launder_page() may be called prior to releasing a page if
+it is still found to be dirty. It returns zero if the page was successfully
+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.
+
        Note: currently almost all instances of address_space methods are
 using BKL for internal serialization and that's one of the worst sources
 of contention. Normally they are calling library functions (in fs/buffer.c)