vfs: make the string hashes salt the hash

We always mixed in the parent pointer into the dentry name hash, but we
did it late at lookup time.  It turns out that we can simplify that
lookup-time action by salting the hash with the parent pointer early
instead of late.

A few other users of our string hashes also wanted to mix in their own
pointers into the hash, and those are updated to use the same mechanism.

Hash users that don't have any particular initial salt can just use the
NULL pointer as a no-salt.

Cc: Vegard Nossum <vegard.nossum@oracle.com>
Cc: George Spelvin <linux@sciencehorizons.net>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 9 insertions, 12 deletions

diff --git a/fs/dcache.c b/fs/dcache.c
index 817c243..9522b8b 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -104,10 +104,8 @@ 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(const struct dentry *parent,
-					unsigned int hash)
+static inline struct hlist_bl_head *d_hash(unsigned int hash)
 {
-	hash += (unsigned long) parent / L1_CACHE_BYTES;
 	return dentry_hashtable + hash_32(hash, d_hash_shift);
 }
 
@@ -488,7 +486,7 @@ void __d_drop(struct dentry *dentry)
 		if (unlikely(IS_ROOT(dentry)))
 			b = &dentry->d_sb->s_anon;
 		else
-			b = d_hash(dentry->d_parent, dentry->d_name.hash);
+			b = d_hash(dentry->d_name.hash);
 
 		hlist_bl_lock(b);
 		__hlist_bl_del(&dentry->d_hash);
@@ -1670,7 +1668,7 @@ struct dentry *d_alloc_name(struct dentry *parent, const char *name)
 	struct qstr q;
 
 	q.name = name;
-	q.hash_len = hashlen_string(name);
+	q.hash_len = hashlen_string(parent, name);
 	return d_alloc(parent, &q);
 }
 EXPORT_SYMBOL(d_alloc_name);
@@ -2094,7 +2092,7 @@ struct dentry *__d_lookup_rcu(const struct dentry *parent,
 {
 	u64 hashlen = name->hash_len;
 	const unsigned char *str = name->name;
-	struct hlist_bl_head *b = d_hash(parent, hashlen_hash(hashlen));
+	struct hlist_bl_head *b = d_hash(hashlen_hash(hashlen));
 	struct hlist_bl_node *node;
 	struct dentry *dentry;
 
@@ -2211,7 +2209,7 @@ 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_head *b = d_hash(hash);
 	struct hlist_bl_node *node;
 	struct dentry *found = NULL;
 	struct dentry *dentry;
@@ -2291,7 +2289,7 @@ struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name)
 	 * calculate the standard hash first, as the d_op->d_hash()
 	 * routine may choose to leave the hash value unchanged.
 	 */
-	name->hash = full_name_hash(name->name, name->len);
+	name->hash = full_name_hash(dir, name->name, name->len);
 	if (dir->d_flags & DCACHE_OP_HASH) {
 		int err = dir->d_op->d_hash(dir, name);
 		if (unlikely(err < 0))
@@ -2364,7 +2362,7 @@ static void __d_rehash(struct dentry * entry, struct hlist_bl_head *b)
 
 static void _d_rehash(struct dentry * entry)
 {
-	__d_rehash(entry, d_hash(entry->d_parent, entry->d_name.hash));
+	__d_rehash(entry, d_hash(entry->d_name.hash));
 }
 
 /**
@@ -2821,7 +2819,7 @@ static void __d_move(struct dentry *dentry, struct dentry *target,
 	 * for the same hash queue because of how unlikely it is.
 	 */
 	__d_drop(dentry);
-	__d_rehash(dentry, d_hash(target->d_parent, target->d_name.hash));
+	__d_rehash(dentry, d_hash(target->d_name.hash));
 
 	/*
 	 * Unhash the target (d_delete() is not usable here).  If exchanging
@@ -2829,8 +2827,7 @@ static void __d_move(struct dentry *dentry, struct dentry *target,
 	 */
 	__d_drop(target);
 	if (exchange) {
-		__d_rehash(target,
-			   d_hash(dentry->d_parent, dentry->d_name.hash));
+		__d_rehash(target, d_hash(dentry->d_name.hash));
 	}
 
 	/* Switch the names.. */