fs/9p: Implement syncfs call back for 9Pfs

FIXME!! what about dotu ?

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>

fs/9p/v9fs.h

@@ -113,6 +113,7 @@ struct v9fs_session_info {
 	struct list_head slist; /* list of sessions registered with v9fs */
 	struct backing_dev_info bdi;
 	struct rw_semaphore rename_sem;
+	struct p9_fid *root_fid; /* Used for file system sync */
 };
 
 struct p9_fid *v9fs_session_init(struct v9fs_session_info *, const char *,

fs/9p/vfs_super.c

@@ -152,7 +152,6 @@ static struct dentry *v9fs_mount(struct file_system_type *fs_type, int flags,
 		retval = PTR_ERR(inode);
 		goto release_sb;
 	}
-
 	root = d_alloc_root(inode);
 	if (!root) {
 		iput(inode);
@@ -184,10 +183,21 @@ static struct dentry *v9fs_mount(struct file_system_type *fs_type, int flags,
 		p9stat_free(st);
 		kfree(st);
 	}
+	v9fs_fid_add(root, fid);
 	retval = v9fs_get_acl(inode, fid);
 	if (retval)
 		goto release_sb;
-	v9fs_fid_add(root, fid);
+	/*
+	 * Add the root fid to session info. This is used
+	 * for file system sync. We want a cloned fid here
+	 * so that we can do a sync_filesystem after a
+	 * shrink_dcache_for_umount
+	 */
+	v9ses->root_fid = v9fs_fid_clone(root);
+	if (IS_ERR(v9ses->root_fid)) {
+		retval = PTR_ERR(v9ses->root_fid);
+		goto release_sb;
+	}
 
 	P9_DPRINTK(P9_DEBUG_VFS, " simple set mount, return 0\n");
 	return dget(sb->s_root);
@@ -198,15 +208,11 @@ close_session:
 	v9fs_session_close(v9ses);
 	kfree(v9ses);
 	return ERR_PTR(retval);
-
 release_sb:
 	/*
-	 * we will do the session_close and root dentry release
-	 * in the below call. But we need to clunk fid, because we haven't
-	 * attached the fid to dentry so it won't get clunked
-	 * automatically.
+	 * we will do the session_close and root dentry
+	 * release in the below call.
 	 */
-	p9_client_clunk(fid);
 	deactivate_locked_super(sb);
 	return ERR_PTR(retval);
 }
@@ -224,7 +230,7 @@ static void v9fs_kill_super(struct super_block *s)
 	P9_DPRINTK(P9_DEBUG_VFS, " %p\n", s);
 
 	kill_anon_super(s);
-
+	p9_client_clunk(v9ses->root_fid);
 	v9fs_session_cancel(v9ses);
 	v9fs_session_close(v9ses);
 	kfree(v9ses);
@@ -277,6 +283,14 @@ done:
 	return res;
 }
 
+static int v9fs_sync_fs(struct super_block *sb, int wait)
+{
+	struct v9fs_session_info *v9ses = sb->s_fs_info;
+
+	P9_DPRINTK(P9_DEBUG_VFS, "v9fs_sync_fs: super_block %p\n", sb);
+	return p9_client_sync_fs(v9ses->root_fid);
+}
+
 static const struct super_operations v9fs_super_ops = {
 #ifdef CONFIG_9P_FSCACHE
 	.alloc_inode = v9fs_alloc_inode,
@@ -293,6 +307,7 @@ static const struct super_operations v9fs_super_ops_dotl = {
 	.alloc_inode = v9fs_alloc_inode,
 	.destroy_inode = v9fs_destroy_inode,
 #endif
+	.sync_fs = v9fs_sync_fs,
 	.statfs = v9fs_statfs,
 	.evict_inode = v9fs_evict_inode,
 	.show_options = generic_show_options,