FS-Cache: Make kAFS use FS-Cache

The attached patch makes the kAFS filesystem in fs/afs/ use FS-Cache, and
through it any attached caches.  The kAFS filesystem will use caching
automatically if it's available.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Steve Dickson <steved@redhat.com>
Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Tested-by: Daire Byrne <Daire.Byrne@framestore.com>

1 files changed, 21 insertions, 0 deletions

diff --git a/fs/afs/write.c b/fs/afs/write.c
index 3fb36d433621..c2e7a7ff0080 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -780,3 +780,24 @@ int afs_fsync(struct file *file, struct dentry *dentry, int datasync)
         _leave(" = %d", ret);
         return ret;
 }
+
+/*
+ * notification that a previously read-only page is about to become writable
+ * - if it returns an error, the caller will deliver a bus error signal
+ */
+int afs_page_mkwrite(struct vm_area_struct *vma, struct page *page)
+{
+        struct afs_vnode *vnode = AFS_FS_I(vma->vm_file->f_mapping->host);
+
+        _enter("{{%x:%u}},{%lx}",
+               vnode->fid.vid, vnode->fid.vnode, page->index);
+
+        /* wait for the page to be written to the cache before we allow it to
+         * be modified */
+#ifdef CONFIG_AFS_FSCACHE
+        fscache_wait_on_page_write(vnode->cache, page);
+#endif
+
+        _leave(" = 0");
+        return 0;
+}