Merge branch 'v4l_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab...

[pandora-kernel.git] / Documentation / filesystems / vfs.txt

diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt
index ed7e5ef..20899e0 100644 (file)
--- a/Documentation/filesystems/vfs.txt
+++ b/Documentation/filesystems/vfs.txt
@@ -534,6 +534,7 @@ struct address_space_operations {
        sector_t (*bmap)(struct address_space *, sector_t);
        int (*invalidatepage) (struct page *, unsigned long);
        int (*releasepage) (struct page *, int);
        sector_t (*bmap)(struct address_space *, sector_t);
        int (*invalidatepage) (struct page *, unsigned long);
        int (*releasepage) (struct page *, int);

+       void (*freepage)(struct page *);

        ssize_t (*direct_IO)(int, struct kiocb *, const struct iovec *iov,
                        loff_t offset, unsigned long nr_segs);
        struct page* (*get_xip_page)(struct address_space *, sector_t,
        ssize_t (*direct_IO)(int, struct kiocb *, const struct iovec *iov,
                        loff_t offset, unsigned long nr_segs);
        struct page* (*get_xip_page)(struct address_space *, sector_t,


@@ -660,11 +661,10 @@ struct address_space_operations {
   releasepage: releasepage is called on PagePrivate pages to indicate
         that the page should be freed if possible.  ->releasepage
         should remove any private data from the page and clear the
   releasepage: releasepage is called on PagePrivate pages to indicate
         that the page should be freed if possible.  ->releasepage
         should remove any private data from the page and clear the

-        PagePrivate flag.  It may also remove the page from the
-        address_space.  If this fails for some reason, it may indicate
-        failure with a 0 return value.
-       This is used in two distinct though related cases.  The first
-        is when the VM finds a clean page with no active users and
+        PagePrivate flag. If releasepage() fails for some reason, it must
+       indicate failure with a 0 return value.
+       releasepage() is used in two distinct though related cases.  The
+       first is when the VM finds a clean page with no active users and

         wants to make it a free page.  If ->releasepage succeeds, the
         page will be removed from the address_space and become free.
 
         wants to make it a free page.  If ->releasepage succeeds, the
         page will be removed from the address_space and become free.
 


@@ -679,6 +679,12 @@ struct address_space_operations {
         need to ensure this.  Possibly it can clear the PageUptodate
         bit if it cannot free private data yet.
 
         need to ensure this.  Possibly it can clear the PageUptodate
         bit if it cannot free private data yet.
 

+  freepage: freepage is called once the page is no longer visible in
+        the page cache in order to allow the cleanup of any private
+       data. Since it may be called by the memory reclaimer, it
+       should not assume that the original address_space mapping still
+       exists, and it should not block.
+

   direct_IO: called by the generic read/write routines to perform
         direct_IO - that is IO requests which bypass the page cache
         and transfer data directly between the storage and the
   direct_IO: called by the generic read/write routines to perform
         direct_IO - that is IO requests which bypass the page cache
         and transfer data directly between the storage and the