[XFS] Add a mechanism for XFS to use the generic quota sync method.

This is now used to issue a delayed allocation flush before reporting
quota, which allows the used space quota report to match reality.
Signed-off-by: Nathan Scott <nathans@sgi.com>

fs/quota.c

@@ -118,6 +118,10 @@ static int xqm_quotactl_valid(struct super_block *sb, int type, int cmd, qid_t i
 			if (!sb->s_qcop->get_xquota)
 				return -ENOSYS;
 			break;
+		case Q_XQUOTASYNC:
+			if (!sb->s_qcop->quota_sync)
+				return -ENOSYS;
+			break;
 		default:
 			return -EINVAL;
 	}
@@ -128,7 +132,7 @@ static int xqm_quotactl_valid(struct super_block *sb, int type, int cmd, qid_t i
 		     (type == XQM_GRPQUOTA && !in_egroup_p(id))) &&
 		     !capable(CAP_SYS_ADMIN))
 			return -EPERM;
-	} else if (cmd != Q_XGETQSTAT) {
+	} else if (cmd != Q_XGETQSTAT && cmd != Q_XQUOTASYNC) {
 		if (!capable(CAP_SYS_ADMIN))
 			return -EPERM;
 	}
@@ -322,6 +326,8 @@ static int do_quotactl(struct super_block *sb, int type, int cmd, qid_t id, void
 				return -EFAULT;
 			return 0;
 		}
+		case Q_XQUOTASYNC:
+			return sb->s_qcop->quota_sync(sb, type);
 		/* We never reach here unless validity check is broken */
 		default:
 			BUG();

include/linux/dqblk_xfs.h

@@ -37,6 +37,7 @@
 #define Q_XSETQLIM	XQM_CMD(4)	/* set disk limits */
 #define Q_XGETQSTAT	XQM_CMD(5)	/* get quota subsystem status */
 #define Q_XQUOTARM	XQM_CMD(6)	/* free disk space used by dquots */
+#define Q_XQUOTASYNC	XQM_CMD(7)	/* delalloc flush, updates dquots */
 
 /*
  * fs_disk_quota structure: