Merge branch 'perf/urgent' into perf/core

Merge reason: We are going to queue up a dependent patch.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 28 insertions, 5 deletions

diff --git a/fs/dcache.c b/fs/dcache.c
index fe19ac13f75f..bcbdb33fcc20 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -104,7 +104,7 @@ static unsigned int d_hash_shift __read_mostly;
 
 static struct hlist_bl_head *dentry_hashtable __read_mostly;
 
-static inline struct hlist_bl_head *d_hash(struct dentry *parent,
+static inline struct hlist_bl_head *d_hash(const struct dentry *parent,
 					unsigned long hash)
 {
 	hash += ((unsigned long) parent ^ GOLDEN_RATIO_PRIME) / L1_CACHE_BYTES;
@@ -137,6 +137,26 @@ int proc_nr_dentry(ctl_table *table, int write, void __user *buffer,
 }
 #endif
 
+/*
+ * Compare 2 name strings, return 0 if they match, otherwise non-zero.
+ * The strings are both count bytes long, and count is non-zero.
+ */
+static inline int dentry_cmp(const unsigned char *cs, size_t scount,
+				const unsigned char *ct, size_t tcount)
+{
+	if (scount != tcount)
+		return 1;
+
+	do {
+		if (*cs != *ct)
+			return 1;
+		cs++;
+		ct++;
+		tcount--;
+	} while (tcount);
+	return 0;
+}
+
 static void __d_free(struct rcu_head *head)
 {
 	struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);
@@ -1717,8 +1737,9 @@ EXPORT_SYMBOL(d_add_ci);
  * child is looked up. Thus, an interlocking stepping of sequence lock checks
  * is formed, giving integrity down the path walk.
  */
-struct dentry *__d_lookup_rcu(struct dentry *parent, struct qstr *name,
-				unsigned *seq, struct inode **inode)
+struct dentry *__d_lookup_rcu(const struct dentry *parent,
+				const struct qstr *name,
+				unsigned *seqp, struct inode **inode)
 {
 	unsigned int len = name->len;
 	unsigned int hash = name->hash;
@@ -1748,6 +1769,7 @@ struct dentry *__d_lookup_rcu(struct dentry *parent, struct qstr *name,
 	 * See Documentation/filesystems/path-lookup.txt for more details.
 	 */
 	hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
+		unsigned seq;
 		struct inode *i;
 		const char *tname;
 		int tlen;
@@ -1756,7 +1778,7 @@ struct dentry *__d_lookup_rcu(struct dentry *parent, struct qstr *name,
 			continue;
 
 seqretry:
-		*seq = read_seqcount_begin(&dentry->d_seq);
+		seq = read_seqcount_begin(&dentry->d_seq);
 		if (dentry->d_parent != parent)
 			continue;
 		if (d_unhashed(dentry))
@@ -1771,7 +1793,7 @@ seqretry:
 		 * edge of memory when walking. If we could load this
 		 * atomically some other way, we could drop this check.
 		 */
-		if (read_seqcount_retry(&dentry->d_seq, *seq))
+		if (read_seqcount_retry(&dentry->d_seq, seq))
 			goto seqretry;
 		if (unlikely(parent->d_flags & DCACHE_OP_COMPARE)) {
 			if (parent->d_op->d_compare(parent, *inode,
@@ -1788,6 +1810,7 @@ seqretry:
 		 * order to do anything useful with the returned dentry
 		 * anyway.
 		 */
+		*seqp = seq;
 		*inode = i;
 		return dentry;
 	}