Merge tag 'pull-dcache' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Pull dcache updates from Al Viro:

 - d_alloc_parallel() API change (Neil's with my changes)

 - NORCU fixes

 - Reorganization and simplification of dentry eviction logic

 - Simplifying rcu_read_lock() scopes in fs/dcache.c

 - Secondary roots work - getting rid of NFS fake root dentries and
   dealing with remaining shrink_dcache_for_umount() and
   shrink_dentry_list() races

 - making cursors NORCU (surprisingly easy)

* tag 'pull-dcache' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (22 commits)
  make cursors NORCU
  nfs: get rid of fake root dentries
  wind ->s_roots via ->d_sib instead of ->d_hash
  shrink_dentry_tree(): unify the calls of shrink_dentry_list()
  shrinking rcu_read_lock() scope in d_alloc_parallel()
  d_walk(): shrink rcu_read_lock() scope
  document dentry_kill()
  adjust calling conventions of lock_for_kill(), fold __dentry_kill() into dentry_kill()
  Document rcu_read_lock() use in select_collect2()
  Shift rcu_read_{,un}lock() inside fast_dput()
  simplify safety for lock_for_kill() slowpath
  fold lock_for_kill() and __dentry_kill() into common helper
  fold lock_for_kill() into shrink_kill()
  shrink_dentry_list(): start with removing from shrink list
  d_prune_aliases(): make sure to skip NORCU aliases
  kill d_dispose_if_unused()
  make to_shrink_list() return whether it has moved dentry to list
  select_collect(): ignore dentries on shrink lists if they have positive refcounts
  find_acceptable_alias(): skip NORCU aliases with zero refcount
  fix a race between d_find_any_alias() and final dput() of NORCU dentries
  ...

3 files changed, 26 insertions, 9 deletions

diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 2577c05f84ec..4b1ff99608e0 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -116,10 +116,7 @@ struct dentry {
 					 * possible!
 					 */
 
-	union {
-		struct list_head d_lru;		/* LRU list */
-		wait_queue_head_t *d_wait;	/* in-lookup ones only */
-	};
+	struct list_head d_lru;		/* LRU list */
 	struct hlist_node d_sib;	/* child of parent list */
 	struct hlist_head d_children;	/* our children */
 	/*
@@ -210,6 +207,9 @@ enum dentry_flags {
 	DCACHE_REFERENCED		= BIT(6),	/* Recently used, don't discard. */
 	DCACHE_DONTCACHE		= BIT(7),	/* Purge from memory on final dput() */
 	DCACHE_CANT_MOUNT		= BIT(8),
+	DCACHE_LOOKUP_WAITERS		= BIT(9),	/* A thread is waiting for
+							 * PAR_LOOKUP to clear
+							 */
 	DCACHE_SHRINK_LIST		= BIT(10),
 	DCACHE_OP_WEAK_REVALIDATE	= BIT(11),
 	/*
@@ -256,8 +256,7 @@ extern void d_delete(struct dentry *);
 /* allocate/de-allocate */
 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
 extern struct dentry * d_alloc_anon(struct super_block *);
-extern struct dentry * d_alloc_parallel(struct dentry *, const struct qstr *,
-					wait_queue_head_t *);
+extern struct dentry * d_alloc_parallel(struct dentry *, const struct qstr *);
 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
 /* weird procfs mess; *NOT* exported */
 extern struct dentry * d_splice_alias_ops(struct inode *, struct dentry *,
@@ -281,7 +280,7 @@ extern void d_tmpfile(struct file *, struct inode *);
 
 extern struct dentry *d_find_alias(struct inode *);
 extern void d_prune_aliases(struct inode *);
-extern void d_dispose_if_unused(struct dentry *, struct list_head *);
+extern bool __move_to_shrink_list(struct dentry *, struct list_head *);
 extern void shrink_dentry_list(struct list_head *);
 
 extern struct dentry *d_find_alias_rcu(struct inode *);
@@ -366,6 +365,24 @@ static inline struct dentry *dget(struct dentry *dentry)
 	return dentry;
 }
 
+/* dentry->d_inode->i_lock must be held by caller */
+static inline bool dget_alias_ilocked(struct dentry *dentry)
+{
+	if (likely(!(READ_ONCE(dentry->d_flags) & DCACHE_NORCU))) {
+		lockref_get(&dentry->d_lockref);
+		return true;
+	}
+	// NORCU dentries with zero refcount MUST NOT be grabbed
+	spin_lock(&dentry->d_lock);
+	if (dentry->d_lockref.count > 0) {
+		dget_dlock(dentry);
+		spin_unlock(&dentry->d_lock);
+		return true;
+	}
+	spin_unlock(&dentry->d_lock);
+	return false;
+}
+
 extern struct dentry *dget_parent(struct dentry *dentry);
 
 /**
diff --git a/include/linux/fs/super_types.h b/include/linux/fs/super_types.h
index aa86e4944dbf..ef7941e9dc79 100644
--- a/include/linux/fs/super_types.h
+++ b/include/linux/fs/super_types.h
@@ -162,7 +162,8 @@ struct super_block {
 	struct unicode_map			*s_encoding;
 	__u16					s_encoding_flags;
 #endif
-	struct hlist_bl_head			s_roots;	/* alternate root dentries for NFS */
+	struct hlist_head			s_roots;	/* alternate root dentries for NFS */
+	spinlock_t				s_roots_lock;
 	struct mount				*s_mounts;	/* list of mounts; _not_ for fs use */
 	struct block_device			*s_bdev;	/* can go away once we use an accessor for @s_bdev_file */
 	struct file				*s_bdev_file;
diff --git a/include/linux/nfs_xdr.h b/include/linux/nfs_xdr.h
index 83ee991cde2b..35ea18a40b66 100644
--- a/include/linux/nfs_xdr.h
+++ b/include/linux/nfs_xdr.h
@@ -1745,7 +1745,6 @@ struct nfs_unlinkdata {
 	struct nfs_removeargs args;
 	struct nfs_removeres res;
 	struct dentry *dentry;
-	wait_queue_head_t wq;
 	const struct cred *cred;
 	struct nfs_fattr dir_attr;
 	long timeout;