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/ceph/inode.c b/fs/ceph/inode.c
index f059b59..99bdef6 100644
--- a/fs/ceph/inode.c
+++ b/fs/ceph/inode.c
@@ -1164,7 +1164,7 @@ int ceph_fill_trace(struct super_block *sb, struct ceph_mds_request *req,
 
 			dname.name = rinfo->dname;
 			dname.len = rinfo->dname_len;
-			dname.hash = full_name_hash(dname.name, dname.len);
+			dname.hash = full_name_hash(parent, dname.name, dname.len);
 			vino.ino = le64_to_cpu(rinfo->targeti.in->ino);
 			vino.snap = le64_to_cpu(rinfo->targeti.in->snapid);
 retry_lookup:
@@ -1508,7 +1508,7 @@ int ceph_readdir_prepopulate(struct ceph_mds_request *req,
 
 		dname.name = rde->name;
 		dname.len = rde->name_len;
-		dname.hash = full_name_hash(dname.name, dname.len);
+		dname.hash = full_name_hash(parent, dname.name, dname.len);
 
 		vino.ino = le64_to_cpu(rde->inode.in->ino);
 		vino.snap = le64_to_cpu(rde->inode.in->snapid);
diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index 2103b82..4e8678a 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -3204,7 +3204,7 @@ static void handle_lease(struct ceph_mds_client *mdsc,
 		WARN_ON(1);
 		goto release;  /* hrm... */
 	}
-	dname.hash = full_name_hash(dname.name, dname.len);
+	dname.hash = full_name_hash(parent, dname.name, dname.len);
 	dentry = d_lookup(parent, &dname);
 	dput(parent);
 	if (!dentry)