d_prune_alias(): just lock the parent and call __dentry_kill()
The only reason for games with ->d_prune() was __d_drop(), which
was needed only to force dput() into killing the sucker off.
Note that lock_parent() can be called under ->i_lock and won't
drop it, so dentry is safe from somebody managing to kill it
under us - it won't happen while we are holding ->i_lock.
__dentry_kill() is called only with ->d_lockref.count being 0
(here and when picked from shrink list) or 1 (dput() and dropping
the ancestors in shrink_dentry_list()), so it will never be called
twice - the first thing it's doing is making ->d_lockref.count
negative and once that happens, nothing will increment it.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/dcache.c b/fs/dcache.c
index 70d102e..d8a77b1 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -770,20 +770,13 @@
hlist_for_each_entry(dentry, &inode->i_dentry, d_alias) {
spin_lock(&dentry->d_lock);
if (!dentry->d_lockref.count) {
- /*
- * inform the fs via d_prune that this dentry
- * is about to be unhashed and destroyed.
- */
- if ((dentry->d_flags & DCACHE_OP_PRUNE) &&
- !d_unhashed(dentry))
- dentry->d_op->d_prune(dentry);
-
- __dget_dlock(dentry);
- __d_drop(dentry);
- spin_unlock(&dentry->d_lock);
- spin_unlock(&inode->i_lock);
- dput(dentry);
- goto restart;
+ struct dentry *parent = lock_parent(dentry);
+ if (likely(!dentry->d_lockref.count)) {
+ __dentry_kill(dentry);
+ goto restart;
+ }
+ if (parent)
+ spin_unlock(&parent->d_lock);
}
spin_unlock(&dentry->d_lock);
}