aufs: dentry op

Implement d_op->d_revalidate().
This is another core part of UDBA (cf. lookup.txt in another commit).
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>

fs/aufs/dentry.c

@@ -735,6 +735,154 @@ out:
 	return err;
 }
 
+static int au_do_h_d_reval(struct dentry *h_dentry, unsigned int flags,
+			   struct dentry *dentry, aufs_bindex_t bindex)
+{
+	int err, valid;
+
+	err = 0;
+	if (!(h_dentry->d_flags & DCACHE_OP_REVALIDATE))
+		goto out;
+
+	AuDbg("b%d\n", bindex);
+	/*
+	 * gave up supporting LOOKUP_CREATE/OPEN for lower fs,
+	 * due to whiteout and branch permission.
+	 */
+	flags &= ~(/*LOOKUP_PARENT |*/ LOOKUP_OPEN | LOOKUP_CREATE
+		   | LOOKUP_FOLLOW | LOOKUP_EXCL);
+	/* it may return tri-state */
+	valid = h_dentry->d_op->d_revalidate(h_dentry, flags);
+
+	if (unlikely(valid < 0))
+		err = valid;
+	else if (!valid)
+		err = -EINVAL;
+
+out:
+	AuTraceErr(err);
+	return err;
+}
+
+/* todo: remove this */
+static int h_d_revalidate(struct dentry *dentry, struct inode *inode,
+			  unsigned int flags, int do_udba)
+{
+	int err;
+	umode_t mode, h_mode;
+	aufs_bindex_t bindex, btail, btop, ibs, ibe;
+	unsigned char plus, unhashed, is_root, h_plus, h_nfs;
+	struct inode *h_inode, *h_cached_inode;
+	struct dentry *h_dentry;
+	struct qstr *name, *h_name;
+
+	err = 0;
+	plus = 0;
+	mode = 0;
+	ibs = -1;
+	ibe = -1;
+	unhashed = !!d_unhashed(dentry);
+	is_root = !!IS_ROOT(dentry);
+	name = &dentry->d_name;
+
+	/*
+	 * Theoretically, REVAL test should be unnecessary in case of
+	 * {FS,I}NOTIFY.
+	 * But {fs,i}notify doesn't fire some necessary events,
+	 *	IN_ATTRIB for atime/nlink/pageio
+	 * Let's do REVAL test too.
+	 */
+	if (do_udba && inode) {
+		mode = (inode->i_mode & S_IFMT);
+		plus = (inode->i_nlink > 0);
+		ibs = au_ibtop(inode);
+		ibe = au_ibbot(inode);
+	}
+
+	btop = au_dbtop(dentry);
+	btail = btop;
+	if (inode && S_ISDIR(inode->i_mode))
+		btail = au_dbtaildir(dentry);
+	for (bindex = btop; bindex <= btail; bindex++) {
+		h_dentry = au_h_dptr(dentry, bindex);
+		if (!h_dentry)
+			continue;
+
+		AuDbg("b%d, %pd\n", bindex, h_dentry);
+		h_nfs = !!au_test_nfs(h_dentry->d_sb);
+		spin_lock(&h_dentry->d_lock);
+		h_name = &h_dentry->d_name;
+		if (unlikely(do_udba
+			     && !is_root
+			     && ((!h_nfs
+				  && (unhashed != !!d_unhashed(h_dentry)
+				      || !au_qstreq(name, h_name)
+					  ))
+				 || (h_nfs
+				     && !(flags & LOOKUP_OPEN)
+				     && (h_dentry->d_flags
+					 & DCACHE_NFSFS_RENAMED)))
+			    )) {
+			int h_unhashed;
+
+			h_unhashed = d_unhashed(h_dentry);
+			spin_unlock(&h_dentry->d_lock);
+			AuDbg("unhash 0x%x 0x%x, %pd %pd\n",
+			      unhashed, h_unhashed, dentry, h_dentry);
+			goto err;
+		}
+		spin_unlock(&h_dentry->d_lock);
+
+		err = au_do_h_d_reval(h_dentry, flags, dentry, bindex);
+		if (unlikely(err))
+			/* do not goto err, to keep the errno */
+			break;
+
+		/* todo: plink too? */
+		if (!do_udba)
+			continue;
+
+		/* UDBA tests */
+		if (unlikely(!!inode != d_is_positive(h_dentry)))
+			goto err;
+
+		h_inode = NULL;
+		if (d_is_positive(h_dentry))
+			h_inode = d_inode(h_dentry);
+		h_plus = plus;
+		h_mode = mode;
+		h_cached_inode = h_inode;
+		if (h_inode) {
+			h_mode = (h_inode->i_mode & S_IFMT);
+			h_plus = (h_inode->i_nlink > 0);
+		}
+		if (inode && ibs <= bindex && bindex <= ibe)
+			h_cached_inode = au_h_iptr(inode, bindex);
+
+		if (!h_nfs) {
+			if (unlikely(plus != h_plus))
+				goto err;
+		} else {
+			if (unlikely(!(h_dentry->d_flags & DCACHE_NFSFS_RENAMED)
+				     && !is_root
+				     && !IS_ROOT(h_dentry)
+				     && unhashed != d_unhashed(h_dentry)))
+				goto err;
+		}
+		if (unlikely(mode != h_mode
+			     || h_cached_inode != h_inode))
+			goto err;
+		continue;
+
+err:
+		err = -EINVAL;
+		break;
+	}
+
+	AuTraceErr(err);
+	return err;
+}
+
 /* todo: consolidate with do_refresh() and au_reval_for_attr() */
 static int simple_reval_dpath(struct dentry *dentry, unsigned int sigen)
 {
@@ -800,3 +948,119 @@ int au_reval_dpath(struct dentry *dentry, unsigned int sigen)
 
 	return err;
 }
+
+/*
+ * if valid returns 1, otherwise 0.
+ */
+static int aufs_d_revalidate(struct dentry *dentry, unsigned int flags)
+{
+	int valid, err;
+	unsigned int sigen;
+	unsigned char do_udba;
+	struct super_block *sb;
+	struct inode *inode;
+
+	/* todo: support rcu-walk? */
+	if (flags & LOOKUP_RCU)
+		return -ECHILD;
+
+	valid = 0;
+	if (unlikely(!au_di(dentry)))
+		goto out;
+
+	valid = 1;
+	sb = dentry->d_sb;
+	/*
+	 * todo: very ugly
+	 * i_mutex of parent dir may be held,
+	 * but we should not return 'invalid' due to busy.
+	 */
+	err = aufs_read_lock(dentry, AuLock_FLUSH | AuLock_DW | AuLock_NOPLM);
+	if (unlikely(err)) {
+		valid = err;
+		AuTraceErr(err);
+		goto out;
+	}
+	inode = NULL;
+	if (d_really_is_positive(dentry))
+		inode = d_inode(dentry);
+	if (unlikely(inode && au_is_bad_inode(inode))) {
+		err = -EINVAL;
+		AuTraceErr(err);
+		goto out_dgrade;
+	}
+	if (unlikely(au_dbrange_test(dentry))) {
+		err = -EINVAL;
+		AuTraceErr(err);
+		goto out_dgrade;
+	}
+
+	sigen = au_sigen(sb);
+	if (au_digen_test(dentry, sigen)) {
+		AuDebugOn(IS_ROOT(dentry));
+		err = au_reval_dpath(dentry, sigen);
+		if (unlikely(err)) {
+			AuTraceErr(err);
+			goto out_dgrade;
+		}
+	}
+	di_downgrade_lock(dentry, AuLock_IR);
+
+	err = -EINVAL;
+	if (!(flags & (LOOKUP_OPEN | LOOKUP_EMPTY))
+	    && inode
+	    && !(inode->i_state && I_LINKABLE)
+	    && (IS_DEADDIR(inode) || !inode->i_nlink)) {
+		AuTraceErr(err);
+		goto out_inval;
+	}
+
+	do_udba = !au_opt_test(au_mntflags(sb), UDBA_NONE);
+	if (do_udba && inode) {
+		aufs_bindex_t btop = au_ibtop(inode);
+		struct inode *h_inode;
+
+		if (btop >= 0) {
+			h_inode = au_h_iptr(inode, btop);
+			if (h_inode && au_test_higen(inode, h_inode)) {
+				AuTraceErr(err);
+				goto out_inval;
+			}
+		}
+	}
+
+	err = h_d_revalidate(dentry, inode, flags, do_udba);
+	if (unlikely(!err && do_udba && au_dbtop(dentry) < 0)) {
+		err = -EIO;
+		AuDbg("both of real entry and whiteout found, %p, err %d\n",
+		      dentry, err);
+	}
+	goto out_inval;
+
+out_dgrade:
+	di_downgrade_lock(dentry, AuLock_IR);
+out_inval:
+	aufs_read_unlock(dentry, AuLock_IR);
+	AuTraceErr(err);
+	valid = !err;
+out:
+	if (!valid) {
+		AuDbg("%pd invalid, %d\n", dentry, valid);
+		d_drop(dentry);
+	}
+	return valid;
+}
+
+static void aufs_d_release(struct dentry *dentry)
+{
+	if (au_di(dentry)) {
+		au_di_fin(dentry);
+		au_hn_di_reinit(dentry);
+	}
+}
+
+const struct dentry_operations aufs_dop = {
+	.d_revalidate		= aufs_d_revalidate,
+	.d_weak_revalidate	= aufs_d_revalidate,
+	.d_release		= aufs_d_release
+};

fs/aufs/dentry.h

@@ -49,6 +49,7 @@ struct au_do_lookup_args {
 /* ---------------------------------------------------------------------- */
 
 /* dentry.c */
+extern const struct dentry_operations aufs_dop;
 struct au_branch;
 struct dentry *au_sio_lkup_one(struct qstr *name, struct dentry *parent);
 int au_h_verify(struct dentry *h_dentry, unsigned int udba, struct inode *h_dir,

fs/aufs/super.c

@@ -772,7 +772,7 @@ static int aufs_fill_super(struct super_block *sb, void *raw_data,
 	sb->s_flags |= SB_NOATIME | SB_NODIRATIME;
 	sb->s_flags |= SB_I_VERSION; /* do we really need this? */
 	sb->s_op = &aufs_sop;
-	sb->s_d_op = &simple_dentry_operations;  /* replace later */
+	sb->s_d_op = &aufs_dop;
 	sb->s_magic = AUFS_SUPER_MAGIC;
 	sb->s_maxbytes = 0;
 	sb->s_stack_depth = 1;