Commit 29355c39 authored May 30, 2014 by Al Viro

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>

parent bbd51924

fs/dcache.c

+7 −14

Original line number	Diff line number	Diff line
		@@ -770,21 +770,14 @@ restart:
		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);
		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);
		}
		spin_unlock(&inode->i_lock);

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