[RFC PATCH 08/25] d_prune_aliases(): make sure to skip NORCU aliases

[Al Viro <viro@zeniv.linux.org.uk>]

Either they are busy (in which case they won't be moved to shrink
list anyway) or they have a zero refcount, in which case we really
shouldn't mess with them - whoever had dropped the refcount to
zero is on the way to evicting and freeing them.

That way we are guaranteed that only the thread that has dropped
refcount of NORCU dentry to zero might call lock_for_kill() and
__dentry_kill() for those.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 fs/dcache.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index 7d8c23a42409..34d57ed9d791 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1200,7 +1200,8 @@ void d_prune_aliases(struct inode *inode)
 	spin_lock(&inode->i_lock);
 	for_each_alias(dentry, inode) {
 		spin_lock(&dentry->d_lock);
-		__move_to_shrink_list(dentry, &dispose);
+		if (likely(!(dentry->d_flags & DCACHE_NORCU)))
+			__move_to_shrink_list(dentry, &dispose);
 		spin_unlock(&dentry->d_lock);
 	}
 	spin_unlock(&inode->i_lock);
-- 
2.47.3