1 files changed, 43 insertions, 99 deletions

diff --git a/fs/dcache.c b/fs/dcache.c
index 5405b89fe8ec..484a52db99ba 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -226,10 +226,9 @@ static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char
 
 static inline int dentry_cmp(const struct dentry *dentry, const unsigned char *ct, unsigned tcount)
 {
-	const unsigned char *cs;
 	/*
 	 * Be careful about RCU walk racing with rename:
-	 * use ACCESS_ONCE to fetch the name pointer.
+	 * use 'lockless_dereference' to fetch the name pointer.
 	 *
 	 * NOTE! Even if a rename will mean that the length
 	 * was not loaded atomically, we don't care. The
@@ -243,8 +242,8 @@ static inline int dentry_cmp(const struct dentry *dentry, const unsigned char *c
 	 * early because the data cannot match (there can
 	 * be no NUL in the ct/tcount data)
 	 */
-	cs = ACCESS_ONCE(dentry->d_name.name);
-	smp_read_barrier_depends();
+	const unsigned char *cs = lockless_dereference(dentry->d_name.name);
+
 	return dentry_string_cmp(cs, ct, tcount);
 }
 
@@ -1812,7 +1811,7 @@ static void __d_instantiate(struct dentry *dentry, struct inode *inode)
 	raw_write_seqcount_begin(&dentry->d_seq);
 	__d_set_inode_and_type(dentry, inode, add_flags);
 	raw_write_seqcount_end(&dentry->d_seq);
-	__fsnotify_d_instantiate(dentry);
+	fsnotify_update_flags(dentry);
 	spin_unlock(&dentry->d_lock);
 }
 
@@ -2064,42 +2063,19 @@ struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
 }
 EXPORT_SYMBOL(d_add_ci);
 
-/*
- * Do the slow-case of the dentry name compare.
- *
- * Unlike the dentry_cmp() function, we need to atomically
- * load the name and length information, so that the
- * filesystem can rely on them, and can use the 'name' and
- * 'len' information without worrying about walking off the
- * end of memory etc.
- *
- * Thus the read_seqcount_retry() and the "duplicate" info
- * in arguments (the low-level filesystem should not look
- * at the dentry inode or name contents directly, since
- * rename can change them while we're in RCU mode).
- */
-enum slow_d_compare {
-	D_COMP_OK,
-	D_COMP_NOMATCH,
-	D_COMP_SEQRETRY,
-};
 
-static noinline enum slow_d_compare slow_dentry_cmp(
-		const struct dentry *parent,
-		struct dentry *dentry,
-		unsigned int seq,
-		const struct qstr *name)
+static inline bool d_same_name(const struct dentry *dentry,
+				const struct dentry *parent,
+				const struct qstr *name)
 {
-	int tlen = dentry->d_name.len;
-	const char *tname = dentry->d_name.name;
-
-	if (read_seqcount_retry(&dentry->d_seq, seq)) {
-		cpu_relax();
-		return D_COMP_SEQRETRY;
+	if (likely(!(parent->d_flags & DCACHE_OP_COMPARE))) {
+		if (dentry->d_name.len != name->len)
+			return false;
+		return dentry_cmp(dentry, name->name, name->len) == 0;
 	}
-	if (parent->d_op->d_compare(parent, dentry, tlen, tname, name))
-		return D_COMP_NOMATCH;
-	return D_COMP_OK;
+	return parent->d_op->d_compare(parent, dentry,
+				       dentry->d_name.len, dentry->d_name.name,
+				       name) == 0;
 }
 
 /**
@@ -2178,6 +2154,9 @@ seqretry:
 		 * dentry compare, we will do seqretries until it is stable,
 		 * and if we end up with a successful lookup, we actually
 		 * want to exit RCU lookup anyway.
+		 *
+		 * Note that raw_seqcount_begin still *does* smp_rmb(), so
+		 * we are still guaranteed NUL-termination of ->d_name.name.
 		 */
 		seq = raw_seqcount_begin(&dentry->d_seq);
 		if (dentry->d_parent != parent)
@@ -2186,24 +2165,28 @@ seqretry:
 			continue;
 
 		if (unlikely(parent->d_flags & DCACHE_OP_COMPARE)) {
+			int tlen;
+			const char *tname;
 			if (dentry->d_name.hash != hashlen_hash(hashlen))
 				continue;
-			*seqp = seq;
-			switch (slow_dentry_cmp(parent, dentry, seq, name)) {
-			case D_COMP_OK:
-				return dentry;
-			case D_COMP_NOMATCH:
-				continue;
-			default:
+			tlen = dentry->d_name.len;
+			tname = dentry->d_name.name;
+			/* we want a consistent (name,len) pair */
+			if (read_seqcount_retry(&dentry->d_seq, seq)) {
+				cpu_relax();
 				goto seqretry;
 			}
+			if (parent->d_op->d_compare(parent, dentry,
+						    tlen, tname, name) != 0)
+				continue;
+		} else {
+			if (dentry->d_name.hash_len != hashlen)
+				continue;
+			if (dentry_cmp(dentry, str, hashlen_len(hashlen)) != 0)
+				continue;
 		}
-
-		if (dentry->d_name.hash_len != hashlen)
-			continue;
 		*seqp = seq;
-		if (!dentry_cmp(dentry, str, hashlen_len(hashlen)))
-			return dentry;
+		return dentry;
 	}
 	return NULL;
 }
@@ -2251,9 +2234,7 @@ EXPORT_SYMBOL(d_lookup);
  */
 struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name)
 {
-	unsigned int len = name->len;
 	unsigned int hash = name->hash;
-	const unsigned char *str = name->name;
 	struct hlist_bl_head *b = d_hash(parent, hash);
 	struct hlist_bl_node *node;
 	struct dentry *found = NULL;
@@ -2292,21 +2273,8 @@ struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name)
 		if (d_unhashed(dentry))
 			goto next;
 
-		/*
-		 * It is safe to compare names since d_move() cannot
-		 * change the qstr (protected by d_lock).
-		 */
-		if (parent->d_flags & DCACHE_OP_COMPARE) {
-			int tlen = dentry->d_name.len;
-			const char *tname = dentry->d_name.name;
-			if (parent->d_op->d_compare(parent, dentry, tlen, tname, name))
-				goto next;
-		} else {
-			if (dentry->d_name.len != len)
-				goto next;
-			if (dentry_cmp(dentry, str, len))
-				goto next;
-		}
+		if (!d_same_name(dentry, parent, name))
+			goto next;
 
 		dentry->d_lockref.count++;
 		found = dentry;
@@ -2459,9 +2427,7 @@ struct dentry *d_alloc_parallel(struct dentry *parent,
 				const struct qstr *name,
 				wait_queue_head_t *wq)
 {
-	unsigned int len = name->len;
 	unsigned int hash = name->hash;
-	const unsigned char *str = name->name;
 	struct hlist_bl_head *b = in_lookup_hash(parent, hash);
 	struct hlist_bl_node *node;
 	struct dentry *new = d_alloc(parent, name);
@@ -2512,17 +2478,8 @@ retry:
 			continue;
 		if (dentry->d_parent != parent)
 			continue;
-		if (parent->d_flags & DCACHE_OP_COMPARE) {
-			int tlen = dentry->d_name.len;
-			const char *tname = dentry->d_name.name;
-			if (parent->d_op->d_compare(parent, dentry, tlen, tname, name))
-				continue;
-		} else {
-			if (dentry->d_name.len != len)
-				continue;
-			if (dentry_cmp(dentry, str, len))
-				continue;
-		}
+		if (!d_same_name(dentry, parent, name))
+			continue;
 		hlist_bl_unlock(b);
 		/* now we can try to grab a reference */
 		if (!lockref_get_not_dead(&dentry->d_lockref)) {
@@ -2549,17 +2506,8 @@ retry:
 			goto mismatch;
 		if (unlikely(d_unhashed(dentry)))
 			goto mismatch;
-		if (parent->d_flags & DCACHE_OP_COMPARE) {
-			int tlen = dentry->d_name.len;
-			const char *tname = dentry->d_name.name;
-			if (parent->d_op->d_compare(parent, dentry, tlen, tname, name))
-				goto mismatch;
-		} else {
-			if (unlikely(dentry->d_name.len != len))
-				goto mismatch;
-			if (unlikely(dentry_cmp(dentry, str, len)))
-				goto mismatch;
-		}
+		if (unlikely(!d_same_name(dentry, parent, name)))
+			goto mismatch;
 		/* OK, it *is* a hashed match; return it */
 		spin_unlock(&dentry->d_lock);
 		dput(new);
@@ -2612,7 +2560,7 @@ static inline void __d_add(struct dentry *dentry, struct inode *inode)
 		raw_write_seqcount_begin(&dentry->d_seq);
 		__d_set_inode_and_type(dentry, inode, add_flags);
 		raw_write_seqcount_end(&dentry->d_seq);
-		__fsnotify_d_instantiate(dentry);
+		fsnotify_update_flags(dentry);
 	}
 	_d_rehash(dentry);
 	if (dir)
@@ -2655,8 +2603,6 @@ EXPORT_SYMBOL(d_add);
 struct dentry *d_exact_alias(struct dentry *entry, struct inode *inode)
 {
 	struct dentry *alias;
-	int len = entry->d_name.len;
-	const char *name = entry->d_name.name;
 	unsigned int hash = entry->d_name.hash;
 
 	spin_lock(&inode->i_lock);
@@ -2670,9 +2616,7 @@ struct dentry *d_exact_alias(struct dentry *entry, struct inode *inode)
 			continue;
 		if (alias->d_parent != entry->d_parent)
 			continue;
-		if (alias->d_name.len != len)
-			continue;
-		if (dentry_cmp(alias, name, len))
+		if (!d_same_name(alias, entry->d_parent, &entry->d_name))
 			continue;
 		spin_lock(&alias->d_lock);
 		if (!d_unhashed(alias)) {
@@ -2903,8 +2847,8 @@ static void __d_move(struct dentry *dentry, struct dentry *target,
 		list_move(&target->d_child, &target->d_parent->d_subdirs);
 		list_move(&dentry->d_child, &dentry->d_parent->d_subdirs);
 		if (exchange)
-			fsnotify_d_move(target);
-		fsnotify_d_move(dentry);
+			fsnotify_update_flags(target);
+		fsnotify_update_flags(dentry);
 	}
 
 	write_seqcount_end(&target->d_seq);