Do that before new dentry is visible anywhere. It does create a new possible state for dentries present in ->d_children/->d_sib - DCACHE_PAR_LOOKUP present, negative, unhashed, not in in-lookup hash chains, refcount positive. Those are going to be skipped by all tree-walkers (both d_walk() callbacks in fs/dcache.c and explicit loops over children/sibling lists elsewhere) and dput() is fine with those. NOTE: dropping the final reference to a "normal" in-lookup dentry (in in-lookup hash) is a bug - somebody must've forgotten to call d_lookup_done() on it and bad things will happen. With those it's OK; if/when we get around to making __dentry_kill() complain about such breakage, remember that predicate to check should *not* be just d_in_lookup(victim) but rather a combination of that with hlist_bl_unhashed(&victim->d_u.d_in_lookup_hash). Might be worth to consider later... Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx> --- fs/dcache.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/fs/dcache.c b/fs/dcache.c index 29db27228d97..9ad7cbb5a6b0 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -2518,13 +2518,19 @@ struct dentry *d_alloc_parallel(struct dentry *parent, unsigned int hash = name->hash; struct hlist_bl_head *b = in_lookup_hash(parent, hash); struct hlist_bl_node *node; - struct dentry *new = d_alloc(parent, name); + struct dentry *new = __d_alloc(parent->d_sb, name); struct dentry *dentry; unsigned seq, r_seq, d_seq; if (unlikely(!new)) return ERR_PTR(-ENOMEM); + new->d_flags |= DCACHE_PAR_LOOKUP; + spin_lock(&parent->d_lock); + new->d_parent = dget_dlock(parent); + hlist_add_head(&new->d_sib, &parent->d_children); + spin_unlock(&parent->d_lock); + retry: rcu_read_lock(); seq = smp_load_acquire(&parent->d_inode->i_dir_seq); @@ -2608,8 +2614,6 @@ struct dentry *d_alloc_parallel(struct dentry *parent, return dentry; } rcu_read_unlock(); - /* we can't take ->d_lock here; it's OK, though. */ - new->d_flags |= DCACHE_PAR_LOOKUP; new->d_wait = wq; hlist_bl_add_head(&new->d_u.d_in_lookup_hash, b); hlist_bl_unlock(b); -- 2.39.5
