fs: dcache per-bucket dcache hash locking

We can turn the dcache hash locking from a global dcache_hash_lock into
per-bucket locking.
Signed-off-by: Nick Piggin <npiggin@kernel.dk>

fs/super.c

@@ -30,6 +30,7 @@
 #include <linux/idr.h>
 #include <linux/mutex.h>
 #include <linux/backing-dev.h>
+#include <linux/rculist_bl.h>
 #include "internal.h"
 
 
@@ -71,7 +72,7 @@ static struct super_block *alloc_super(struct file_system_type *type)
 		INIT_LIST_HEAD(&s->s_files);
 #endif
 		INIT_LIST_HEAD(&s->s_instances);
-		INIT_HLIST_HEAD(&s->s_anon);
+		INIT_HLIST_BL_HEAD(&s->s_anon);
 		INIT_LIST_HEAD(&s->s_inodes);
 		INIT_LIST_HEAD(&s->s_dentry_lru);
 		init_rwsem(&s->s_umount);

include/linux/dcache.h

@@ -4,6 +4,7 @@
 #include <asm/atomic.h>
 #include <linux/list.h>
 #include <linux/rculist.h>
+#include <linux/rculist_bl.h>
 #include <linux/spinlock.h>
 #include <linux/seqlock.h>
 #include <linux/cache.h>
@@ -95,7 +96,7 @@ struct dentry {
 	/* RCU lookup touched fields */
 	unsigned int d_flags;		/* protected by d_lock */
 	seqcount_t d_seq;		/* per dentry seqlock */
-	struct hlist_node d_hash;	/* lookup hash list */
+	struct hlist_bl_node d_hash;	/* lookup hash list */
 	struct dentry *d_parent;	/* parent directory */
 	struct qstr d_name;
 	struct inode *d_inode;		/* Where the name belongs to - NULL is

include/linux/fs.h

@@ -392,6 +392,7 @@ struct inodes_stat_t {
 #include <linux/capability.h>
 #include <linux/semaphore.h>
 #include <linux/fiemap.h>
+#include <linux/rculist_bl.h>
 
 #include <asm/atomic.h>
 #include <asm/byteorder.h>
@@ -1377,7 +1378,7 @@ struct super_block {
 	const struct xattr_handler **s_xattr;
 
 	struct list_head	s_inodes;	/* all inodes */
-	struct hlist_head	s_anon;		/* anonymous dentries for (nfs) exporting */
+	struct hlist_bl_head	s_anon;		/* anonymous dentries for (nfs) exporting */
 #ifdef CONFIG_SMP
 	struct list_head __percpu *s_files;
 #else