Merge branch 'salted-string-hash'

This changes the vfs dentry hashing to mix in the parent pointer at the
_beginning_ of the hash, rather than at the end.

That actually improves both the hash and the code generation, because we
can move more of the computation to the "static" part of the dcache
setup, and do less at lookup runtime.

It turns out that a lot of other hash users also really wanted to mix in
a base pointer as a 'salt' for the hash, and so the slightly extended
interface ends up working well for other cases too.

Users that want a string hash that is purely about the string pass in a
'salt' pointer of NULL.

* merge branch 'salted-string-hash':
  fs/dcache.c: Save one 32-bit multiply in dcache lookup
  vfs: make the string hashes salt the hash

2 files changed, 3 insertions, 3 deletions

diff --git a/fs/fat/namei_msdos.c b/fs/fat/namei_msdos.c
index b7e2b33aa793..1337c0c7527d 100644
--- a/fs/fat/namei_msdos.c
+++ b/fs/fat/namei_msdos.c
@@ -154,7 +154,7 @@ static int msdos_hash(const struct dentry *dentry, struct qstr *qstr)
 
 	error = msdos_format_name(qstr->name, qstr->len, msdos_name, options);
 	if (!error)
-		qstr->hash = full_name_hash(msdos_name, MSDOS_NAME);
+		qstr->hash = full_name_hash(dentry, msdos_name, MSDOS_NAME);
 	return 0;
 }
 
diff --git a/fs/fat/namei_vfat.c b/fs/fat/namei_vfat.c
index 7092584f424a..6ccdf3f34f90 100644
--- a/fs/fat/namei_vfat.c
+++ b/fs/fat/namei_vfat.c
@@ -107,7 +107,7 @@ static unsigned int vfat_striptail_len(const struct qstr *qstr)
  */
 static int vfat_hash(const struct dentry *dentry, struct qstr *qstr)
 {
-	qstr->hash = full_name_hash(qstr->name, vfat_striptail_len(qstr));
+	qstr->hash = full_name_hash(dentry, qstr->name, vfat_striptail_len(qstr));
 	return 0;
 }
 
@@ -127,7 +127,7 @@ static int vfat_hashi(const struct dentry *dentry, struct qstr *qstr)
 	name = qstr->name;
 	len = vfat_striptail_len(qstr);
 
-	hash = init_name_hash();
+	hash = init_name_hash(dentry);
 	while (len--)
 		hash = partial_name_hash(nls_tolower(t, *name++), hash);
 	qstr->hash = end_name_hash(hash);