aufs: writable branch 3/3, diropq

The functions to create/delete the opaque directory marker (called
'diropq') on the added writable branch.
For details, refer to previous commit.
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>

fs/aufs/whout.c

@@ -12,6 +12,13 @@
 
 #define WH_MASK			0444
 
+/*
+ * If a directory contains this file, then it is opaque.  We start with the
+ * .wh. flag so that it is blocked by lookup.
+ */
+static struct qstr diropq_name = QSTR_INIT(AUFS_WH_DIROPQ,
+					   sizeof(AUFS_WH_DIROPQ) - 1);
+
 /*
  * generate whiteout name, which is NOT terminated by NULL.
  * @name: original d_name.name
@@ -83,6 +90,20 @@ out:
 	return err;
 }
 
+/*
+ * test if the @h_dentry sets opaque or not.
+ */
+int au_diropq_test(struct dentry *h_dentry)
+{
+	int err;
+	struct inode *h_dir;
+
+	h_dir = d_inode(h_dentry);
+	err = au_wh_test(h_dentry, &diropq_name,
+			 au_test_h_perm_sio(h_dir, MAY_EXEC));
+	return err;
+}
+
 /* ---------------------------------------------------------------------- */
 /*
  * functions for removing a whiteout
@@ -545,6 +566,86 @@ out:
 
 /* ---------------------------------------------------------------------- */
 
+/*
+ * create or remove the diropq.
+ */
+static struct dentry *do_diropq(struct dentry *dentry, aufs_bindex_t bindex,
+				unsigned int flags)
+{
+	struct dentry *opq_dentry, *h_dentry;
+	struct super_block *sb;
+	struct au_branch *br;
+	int err;
+
+	sb = dentry->d_sb;
+	br = au_sbr(sb, bindex);
+	h_dentry = au_h_dptr(dentry, bindex);
+	opq_dentry = vfsub_lkup_one(&diropq_name, h_dentry);
+	if (IS_ERR(opq_dentry))
+		goto out;
+
+	if (au_ftest_diropq(flags, CREATE)) {
+		err = link_or_create_wh(sb, bindex, opq_dentry);
+		if (!err) {
+			au_set_dbdiropq(dentry, bindex);
+			goto out; /* success */
+		}
+	} else {
+		struct path tmp = {
+			.dentry = opq_dentry,
+			.mnt	= au_br_mnt(br)
+		};
+		err = do_unlink_wh(au_h_iptr(d_inode(dentry), bindex), &tmp);
+		if (!err)
+			au_set_dbdiropq(dentry, -1);
+	}
+	dput(opq_dentry);
+	opq_dentry = ERR_PTR(err);
+
+out:
+	return opq_dentry;
+}
+
+struct do_diropq_args {
+	struct dentry **errp;
+	struct dentry *dentry;
+	aufs_bindex_t bindex;
+	unsigned int flags;
+};
+
+static void call_do_diropq(void *args)
+{
+	struct do_diropq_args *a = args;
+	*a->errp = do_diropq(a->dentry, a->bindex, a->flags);
+}
+
+struct dentry *au_diropq_sio(struct dentry *dentry, aufs_bindex_t bindex,
+			     unsigned int flags)
+{
+	struct dentry *diropq, *h_dentry;
+
+	h_dentry = au_h_dptr(dentry, bindex);
+	if (!au_test_h_perm_sio(d_inode(h_dentry), MAY_EXEC | MAY_WRITE))
+		diropq = do_diropq(dentry, bindex, flags);
+	else {
+		int wkq_err;
+		struct do_diropq_args args = {
+			.errp		= &diropq,
+			.dentry		= dentry,
+			.bindex		= bindex,
+			.flags		= flags
+		};
+
+		wkq_err = au_wkq_wait(call_do_diropq, &args);
+		if (unlikely(wkq_err))
+			diropq = ERR_PTR(wkq_err);
+	}
+
+	return diropq;
+}
+
+/* ---------------------------------------------------------------------- */
+
 /*
  * lookup whiteout dentry.
  * @h_parent: lower parent dentry which must exist and be locked

fs/aufs/whout.h

@@ -17,6 +17,7 @@ struct qstr;
 int au_wh_name_alloc(struct qstr *wh, const struct qstr *name);
 struct dentry;
 int au_wh_test(struct dentry *h_parent, struct qstr *wh_name, int try_sio);
+int au_diropq_test(struct dentry *h_dentry);
 struct inode;
 struct path;
 int au_wh_unlink_dentry(struct inode *h_dir, struct path *h_path,
@@ -25,10 +26,33 @@ struct au_branch;
 struct super_block;
 int au_wh_init(struct au_branch *br, struct super_block *sb);
 
+/* diropq flags */
+#define AuDiropq_CREATE	1
+#define au_ftest_diropq(flags, name)	((flags) & AuDiropq_##name)
+#define au_fset_diropq(flags, name) \
+	do { (flags) |= AuDiropq_##name; } while (0)
+#define au_fclr_diropq(flags, name) \
+	do { (flags) &= ~AuDiropq_##name; } while (0)
+
+struct dentry *au_diropq_sio(struct dentry *dentry, aufs_bindex_t bindex,
+			     unsigned int flags);
 struct dentry *au_wh_lkup(struct dentry *h_parent, struct qstr *base_name,
 			  struct au_branch *br);
 struct dentry *au_wh_create(struct dentry *dentry, aufs_bindex_t bindex,
 			    struct dentry *h_parent);
 
+/* ---------------------------------------------------------------------- */
+
+static inline struct dentry *au_diropq_create(struct dentry *dentry,
+					      aufs_bindex_t bindex)
+{
+	return au_diropq_sio(dentry, bindex, AuDiropq_CREATE);
+}
+
+static inline int au_diropq_remove(struct dentry *dentry, aufs_bindex_t bindex)
+{
+	return PTR_ERR(au_diropq_sio(dentry, bindex, !AuDiropq_CREATE));
+}
+
 #endif /* __KERNEL__ */
 #endif /* __AUFS_WHOUT_H__ */

include/uapi/linux/aufs_type.h

@@ -81,6 +81,9 @@ typedef int16_t aufs_bindex_t;
 #define AUFS_PLINK_MAINT_DIR	"fs/" AUFS_NAME
 #define AUFS_PLINK_MAINT_PATH	AUFS_PLINK_MAINT_DIR "/" AUFS_PLINK_MAINT_NAME
 
+#define AUFS_DIROPQ_NAME	AUFS_WH_PFX ".opq" /* whiteouted doubly */
+#define AUFS_WH_DIROPQ		AUFS_WH_PFX AUFS_DIROPQ_NAME
+
 #define AUFS_BASE_NAME		AUFS_WH_PFX AUFS_NAME
 #define AUFS_PLINKDIR_NAME	AUFS_WH_PFX "plnk"
 #define AUFS_ORPHDIR_NAME	AUFS_WH_PFX "orph"