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Revert "fs: use RCU read side protection in d_validate" 

This reverts commit 3825bdb7ed.

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

Signed-off-by: Nick Piggin <npiggin@kernel.dk>
This commit is contained in:
Nick Piggin 2011-01-05 20:01:21 +11:00
parent 3c0eee3fe6
commit d3a23e1678
1 changed files with 19 additions and 12 deletions
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31
fs/dcache.c
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@ -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);