quota: Fix race between dqput() and dquot_scan_active()

[~andy/linux] / fs / quota / dquot.c

diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index 831d49a4111f8405716d96ff6a451fc9ebd59e91..cfc8dcc160437c0daacd234f43d29faeb9b2fd33 100644 (file)
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -581,9 +581,17 @@ int dquot_scan_active(struct super_block *sb,
                dqstats_inc(DQST_LOOKUPS);
                dqput(old_dquot);
                old_dquot = dquot;
-               ret = fn(dquot, priv);
-               if (ret < 0)
-                       goto out;
+               /*
+                * ->release_dquot() can be racing with us. Our reference
+                * protects us from new calls to it so just wait for any
+                * outstanding call and recheck the DQ_ACTIVE_B after that.
+                */
+               wait_on_dquot(dquot);
+               if (test_bit(DQ_ACTIVE_B, &dquot->dq_flags)) {
+                       ret = fn(dquot, priv);
+                       if (ret < 0)
+                               goto out;
+               }
                spin_lock(&dq_list_lock);
                /* We are safe to continue now because our dquot could not
                 * be moved out of the inuse list while we hold the reference */