@@ -61,6 +61,48 @@ static void ll_release(struct dentry *de)
call_rcu(&lld->lld_rcu_head, free_dentry_data);
}
+/* Compare if two dentries are the same. Don't match if the existing dentry
+ * is marked invalid. Returns 1 if different, 0 if the same.
+ *
+ * This avoids a race where ll_lookup_it() instantiates a dentry, but we get
+ * an AST before calling d_revalidate_it(). The dentry still exists (marked
+ * INVALID) so d_lookup() matches it, but we have no lock on it (so
+ * lock_match() fails) and we spin around real_lookup().
+ *
+ * This race doesn't apply to lookups in d_alloc_parallel(), and for
+ * those we want to ensure that only one dentry with a given name is
+ * in ll_lookup_nd() at a time. So allow invalid dentries to match
+ * while d_in_lookup(). We will be called again when the lookup
+ * completes, and can give a different answer then.
+ */
+static int ll_dcompare(const struct dentry *dentry,
+ unsigned int len, const char *str,
+ const struct qstr *name)
+{
+ if (len != name->len)
+ return 1;
+
+ if (memcmp(str, name->name, len))
+ return 1;
+
+ CDEBUG(D_DENTRY, "found name %.*s(%p) flags %#x refc %d\n",
+ name->len, name->name, dentry, dentry->d_flags,
+ d_count(dentry));
+
+ /* mountpoint is always valid */
+ if (d_mountpoint(dentry))
+ return 0;
+
+ /* ensure exclusion against parallel lookup of the same name */
+ if (d_in_lookup((struct dentry *)dentry))
+ return 0;
+
+ if (d_lustre_invalid(dentry))
+ return 1;
+
+ return 0;
+}
+
/**
* Called when last reference to a dentry is dropped and dcache wants to know
* whether or not it should cache it:
@@ -202,16 +244,6 @@ static int ll_revalidate_dentry(struct dentry *dentry,
{
struct inode *dir = d_inode(dentry->d_parent);
- CDEBUG(D_VFSTRACE, "VFS Op:name=%s, flags=%u\n",
- dentry->d_name.name, lookup_flags);
-
- /* mountpoint is always valid */
- if (d_mountpoint(dentry))
- return 1;
-
- if (d_lustre_invalid(dentry))
- return 0;
-
/* If this is intermediate component path lookup and we were able to get
* to this dentry, then its lock has not been revoked and the
* path component is valid.
@@ -258,4 +290,5 @@ static int ll_revalidate_nd(struct dentry *dentry, unsigned int flags)
.d_revalidate = ll_revalidate_nd,
.d_release = ll_release,
.d_delete = ll_ddelete,
+ .d_compare = ll_dcompare,
};