kill DCACHE_MAY_FREE

With the new ordering in __dentry_kill() it has become redundant -
it's set if and only if both DCACHE_DENTRY_KILLED and DCACHE_SHRINK_LIST
are set.

We set it in __dentry_kill(), after having set DCACHE_DENTRY_KILLED
with the only condition being that DCACHE_SHRINK_LIST is there;
all of that is done without dropping ->d_lock and the only place
that checks that flag (shrink_dentry_list()) does so under ->d_lock,
after having found the victim on its shrink list.  Since DCACHE_SHRINK_LIST
is set only when placing dentry into shrink list and removed only by
shrink_dentry_list() itself, a check for DCACHE_DENTRY_KILLED in
there would be equivalent to check for DCACHE_MAY_FREE.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Author: Al Viro

fs/dcache.c

@@ -614,10 +614,8 @@ static struct dentry *__dentry_kill(struct dentry *dentry)
 	}
 	spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
 	dentry_unlist(dentry);
-	if (dentry->d_flags & DCACHE_SHRINK_LIST) {
-		dentry->d_flags |= DCACHE_MAY_FREE;
+	if (dentry->d_flags & DCACHE_SHRINK_LIST)
 		can_free = false;
-	}
 	spin_unlock(&dentry->d_lock);
 	if (likely(can_free))
 		dentry_free(dentry);
@@ -1072,7 +1070,7 @@ void shrink_dentry_list(struct list_head *list)
 			bool can_free;
 			rcu_read_unlock();
 			d_shrink_del(dentry);
-			can_free = dentry->d_flags & DCACHE_MAY_FREE;
+			can_free = dentry->d_flags & DCACHE_DENTRY_KILLED;
 			spin_unlock(&dentry->d_lock);
 			if (can_free)
 				dentry_free(dentry);

include/linux/dcache.h

@@ -202,7 +202,6 @@ struct dentry_operations {
 #define DCACHE_SPECIAL_TYPE		(5 << 20) /* Other file type */
 #define DCACHE_SYMLINK_TYPE		(6 << 20) /* Symlink */
 
-#define DCACHE_MAY_FREE			BIT(23)
 #define DCACHE_NOKEY_NAME		BIT(25) /* Encrypted name encoded without key */
 #define DCACHE_OP_REAL			BIT(26)