[PATCH 23/29] vfs: make the string hashes salt the hash

[Sebastian Huber]

From: Linus Torvalds <torvalds at linux-foundation.org>

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

1	1	cpukit/libfs/src/jffs2/src/dir-rtems.c
2	1	cpukit/libfs/src/jffs2/src/os-rtems.h
1	1	cpukit/libfs/src/jffs2/src/readinode.c
1	1	cpukit/libfs/src/jffs2/src/scan.c
2	2	cpukit/libfs/src/jffs2/src/write.c

diff --git a/cpukit/libfs/src/jffs2/src/dir-rtems.c b/cpukit/libfs/src/jffs2/src/dir-rtems.c
index 8d3c3bdc2c..9fa70bcec4 100644
--- a/cpukit/libfs/src/jffs2/src/dir-rtems.c
+++ b/cpukit/libfs/src/jffs2/src/dir-rtems.c
@@ -30,7 +30,7 @@ struct _inode *jffs2_lookup(struct _inode *dir_i, const unsigned char *name, siz
 	struct jffs2_inode_info *dir_f;
 	struct jffs2_full_dirent *fd = NULL, *fd_list;
 	uint32_t ino = 0;
-	uint32_t hash = full_name_hash(name, namelen);
+	uint32_t hash = full_name_hash(NULL, name, namelen);
 	struct _inode *inode = NULL;
 
 	D1(printk("jffs2_lookup()\n"));
diff --git a/cpukit/libfs/src/jffs2/src/os-rtems.h b/cpukit/libfs/src/jffs2/src/os-rtems.h
index ab4f6d72bf..db1be61e67 100644
--- a/cpukit/libfs/src/jffs2/src/os-rtems.h
+++ b/cpukit/libfs/src/jffs2/src/os-rtems.h
@@ -41,9 +41,10 @@
 struct _inode;
 struct super_block;
 
-static inline unsigned int full_name_hash(const unsigned char * name, size_t len) {
+static inline unsigned int full_name_hash(const void *salt, const unsigned char * name, size_t len) {
 
 	uint32_t hash = 0;
+	(void)salt;
  	while (len--) {
 		hash = (hash << 4) | (hash >> 28);
 		hash ^= *(name++);
diff --git a/cpukit/libfs/src/jffs2/src/readinode.c b/cpukit/libfs/src/jffs2/src/readinode.c
index ba1ad6a22f..7a897b670d 100644
--- a/cpukit/libfs/src/jffs2/src/readinode.c
+++ b/cpukit/libfs/src/jffs2/src/readinode.c
@@ -683,7 +683,7 @@ static inline int read_direntry(struct jffs2_sb_info *c, struct jffs2_raw_node_r
 		}
 	}
 
-	fd->nhash = full_name_hash(fd->name, rd->nsize);
+	fd->nhash = full_name_hash(NULL, fd->name, rd->nsize);
 	fd->next = NULL;
 	fd->name[rd->nsize] = '\0';
 
diff --git a/cpukit/libfs/src/jffs2/src/scan.c b/cpukit/libfs/src/jffs2/src/scan.c
index 10bf007819..177a0cdd3f 100644
--- a/cpukit/libfs/src/jffs2/src/scan.c
+++ b/cpukit/libfs/src/jffs2/src/scan.c
@@ -1103,7 +1103,7 @@ static int jffs2_scan_dirent_node(struct jffs2_sb_info *c, struct jffs2_eraseblo
 	fd->next = NULL;
 	fd->version = je32_to_cpu(rd->version);
 	fd->ino = je32_to_cpu(rd->ino);
-	fd->nhash = full_name_hash(fd->name, checkedlen);
+	fd->nhash = full_name_hash(NULL, fd->name, checkedlen);
 	fd->type = rd->type;
 	jffs2_add_fd_to_list(c, fd, &ic->scan_dents);
 
diff --git a/cpukit/libfs/src/jffs2/src/write.c b/cpukit/libfs/src/jffs2/src/write.c
index ac3ec295d5..3d49ec05ca 100644
--- a/cpukit/libfs/src/jffs2/src/write.c
+++ b/cpukit/libfs/src/jffs2/src/write.c
@@ -247,7 +247,7 @@ struct jffs2_full_dirent *jffs2_write_dirent(struct jffs2_sb_info *c, struct jff
 
 	fd->version = je32_to_cpu(rd->version);
 	fd->ino = je32_to_cpu(rd->ino);
-	fd->nhash = full_name_hash(name, namelen);
+	fd->nhash = full_name_hash(NULL, name, namelen);
 	fd->type = rd->type;
 	memcpy(fd->name, name, namelen);
 	fd->name[namelen]=0;
@@ -600,7 +600,7 @@ int jffs2_do_unlink(struct jffs2_sb_info *c, struct jffs2_inode_info *dir_f,
 		jffs2_add_fd_to_list(c, fd, &dir_f->dents);
 		mutex_unlock(&dir_f->sem);
 	} else {
-		uint32_t nhash = full_name_hash(name, namelen);
+		uint32_t nhash = full_name_hash(NULL, name, namelen);
 
 		fd = dir_f->dents;
 		/* We don't actually want to reserve any space, but we do
-- 
2.13.7