[PATCH 56/67] aufs 'robr', aufs as readonly branch of another aufs

[hooanon05@yahoo.co.jp]

From: Junjiro Okajima <hooanon05@yahoo.co.jp>

	initial commit
	aufs 'robr', aufs as readonly branch of another aufs

Signed-off-by: Junjiro Okajima <hooanon05@yahoo.co.jp>
---
 fs/aufs/robr.c |  111 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 111 insertions(+), 0 deletions(-)

diff --git a/fs/aufs/robr.c b/fs/aufs/robr.c
new file mode 100644
index 0000000..0e508bc
--- /dev/null
+++ b/fs/aufs/robr.c
@@ -0,0 +1,111 @@
+/*
+ * Copyright (C) 2008 Junjiro Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+/*
+ * 'robr', aufs as readonly branch of another aufs
+ *
+ * $Id: robr.c,v 1.2 2008/05/12 00:26:53 sfjro Exp $
+ */
+
+#include "aufs.h"
+
+/* ---------------------------------------------------------------------- */
+
+int au_test_robr_wh(struct qstr *name, struct dentry *h_parent,
+		    struct qstr *wh_name, int try_sio, struct au_ndx *ndx)
+{
+	if (strncmp(name->name, AUFS_WH_PFX, AUFS_WH_PFX_LEN))
+		return au_wh_test(h_parent, wh_name, try_sio, ndx);
+	return -EPERM;
+}
+
+int au_test_robr_shwh(struct super_block *sb, const struct qstr *name)
+{
+	return 0;
+}
+
+/* ---------------------------------------------------------------------- */
+
+struct au_robr_lvma {
+	struct list_head list;
+	struct vm_area_struct *vma;
+};
+
+struct file *au_robr_safe_file(struct vm_area_struct *vma)
+{
+	struct file *file = vma->vm_file;
+	struct super_block *sb = file->f_dentry->d_sb;
+	struct au_robr_lvma *lvma, *entry;
+	struct au_sbinfo *sbinfo;
+	int found, warn;
+
+	AuTraceEnter();
+	AuDebugOn(!au_test_aufs(sb));
+
+	warn = 0;
+	found = 0;
+	sbinfo = au_sbi(sb);
+	spin_lock(&sbinfo->si_lvma_lock);
+	list_for_each_entry(entry, &sbinfo->si_lvma, list) {
+		found = (entry->vma == vma);
+		if (unlikely(found))
+			break;
+	}
+	if (!found) {
+		lvma = kmalloc(sizeof(*lvma), GFP_ATOMIC);
+		if (lvma) {
+			lvma->vma = vma;
+			list_add(&lvma->list, &sbinfo->si_lvma);
+		} else {
+			warn = 1;
+			file = NULL;
+		}
+	} else
+		file = NULL;
+	spin_unlock(&sbinfo->si_lvma_lock);
+
+	if (unlikely(warn))
+		AuWarn1("no memory for lvma\n");
+	return file;
+}
+
+void au_robr_reset_file(struct vm_area_struct *vma, struct file *file)
+{
+	struct super_block *sb = file->f_dentry->d_sb;
+	struct au_robr_lvma *entry, *found;
+	struct au_sbinfo *sbinfo;
+
+	AuTraceEnter();
+	AuDebugOn(!au_test_aufs(sb));
+
+	vma->vm_file = file;
+	//smp_mb(); /* flush vm_file */
+
+	found = NULL;
+	sbinfo = au_sbi(sb);
+	spin_lock(&sbinfo->si_lvma_lock);
+	list_for_each_entry(entry, &sbinfo->si_lvma, list)
+		if (entry->vma == vma) {
+			found = entry;
+			break;
+		}
+	AuDebugOn(!found);
+	list_del(&found->list);
+	spin_unlock(&sbinfo->si_lvma_lock);
+	kfree(found);
+}
-- 
1.4.4.4