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Commit d3a23e16 authored by Nick Piggin's avatar Nick Piggin
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Revert "fs: use RCU read side protection in d_validate" 



This reverts commit 3825bdb7.

You cannot dget() a dentry without having a reference, or holding
a lock that guarantees it remains valid.

Signed-off-by: default avatarNick Piggin <npiggin@kernel.dk>
parent 3c0eee3f

fs/dcache.c

+19 −12
Original line number Diff line number Diff line
@@ -1491,26 +1491,33 @@ struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name) 
 * This is used by ncpfs in its readdir implementation.

 * Zero is returned in the dentry is invalid.

 */

int d_validate(struct dentry *dentry, struct dentry *parent)

 

int d_validate(struct dentry *dentry, struct dentry *dparent)

{

	struct hlist_head *head = d_hash(parent, dentry->d_name.hash);

	struct hlist_node *node;

	struct dentry *d;

	struct hlist_head *base;

	struct hlist_node *lhp;



	/* Check whether the ptr might be valid at all.. */

	if (!kmem_ptr_validate(dentry_cache, dentry))

		return 0;

	if (dentry->d_parent != parent)

		return 0;

		goto out;



	rcu_read_lock();

	hlist_for_each_entry_rcu(d, node, head, d_hash) {

		if (d == dentry) {

			dget(dentry);

	if (dentry->d_parent != dparent)

		goto out;



	spin_lock(&dcache_lock);

	base = d_hash(dparent, dentry->d_name.hash);

	hlist_for_each(lhp,base) { 

		/* hlist_for_each_entry_rcu() not required for d_hash list

		 * as it is parsed under dcache_lock

		 */

		if (dentry == hlist_entry(lhp, struct dentry, d_hash)) {

			__dget_locked(dentry);

			spin_unlock(&dcache_lock);

			return 1;

		}

	}

	rcu_read_unlock();

	spin_unlock(&dcache_lock);

out:

	return 0;

}

EXPORT_SYMBOL(d_validate);