xfs: don't lose solo dquot update transactions

Quota counter updates are tracked via incore objects which hang off the
xfs_trans object.  These changes are then turned into dirty log items in
xfs_trans_apply_dquot_deltas just prior to commiting the log items to
the CIL.

However, updating the incore deltas do not cause XFS_TRANS_DIRTY to be
set on the transaction.  In other words, a pure quota counter update
will be silently discarded if there are no other dirty log items
attached to the transaction.

This is currently not the case anywhere in the filesystem because quota
updates always dirty at least one other metadata item, but a subsequent
bug fix will add dquot log item precommits, so we actually need a dirty
dquot log item prior to xfs_trans_run_precommits.  Also let's not leave
a logic bomb.

Cc: <stable@vger.kernel.org> # v2.6.35
Fixes: 0924378 ("xfs: split out iclog writing from xfs_trans_commit()")
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

Author: Darrick J. Wong

fs/xfs/xfs_quota.h

@@ -101,7 +101,8 @@ extern void xfs_trans_free_dqinfo(struct xfs_trans *);
 extern void xfs_trans_mod_dquot_byino(struct xfs_trans *, struct xfs_inode *,
 		uint, int64_t);
 extern void xfs_trans_apply_dquot_deltas(struct xfs_trans *);
-extern void xfs_trans_unreserve_and_mod_dquots(struct xfs_trans *);
+void xfs_trans_unreserve_and_mod_dquots(struct xfs_trans *tp,
+		bool already_locked);
 int xfs_trans_reserve_quota_nblks(struct xfs_trans *tp, struct xfs_inode *ip,
 		int64_t dblocks, int64_t rblocks, bool force);
 extern int xfs_trans_reserve_quota_bydquots(struct xfs_trans *,
@@ -173,7 +174,7 @@ static inline void xfs_trans_mod_dquot_byino(struct xfs_trans *tp,
 {
 }
 #define xfs_trans_apply_dquot_deltas(tp)
-#define xfs_trans_unreserve_and_mod_dquots(tp)
+#define xfs_trans_unreserve_and_mod_dquots(tp, a)
 static inline int xfs_trans_reserve_quota_nblks(struct xfs_trans *tp,
 		struct xfs_inode *ip, int64_t dblocks, int64_t rblocks,
 		bool force)

fs/xfs/xfs_trans.c

@@ -866,6 +866,7 @@ __xfs_trans_commit(
 	 */
 	if (tp->t_flags & XFS_TRANS_SB_DIRTY)
 		xfs_trans_apply_sb_deltas(tp);
+	xfs_trans_apply_dquot_deltas(tp);
 
 	error = xfs_trans_run_precommits(tp);
 	if (error)
@@ -894,11 +895,6 @@ __xfs_trans_commit(
 
 	ASSERT(tp->t_ticket != NULL);
 
-	/*
-	 * If we need to update the superblock, then do it now.
-	 */
-	xfs_trans_apply_dquot_deltas(tp);
-
 	xlog_cil_commit(log, tp, &commit_seq, regrant);
 
 	xfs_trans_free(tp);
@@ -924,7 +920,7 @@ __xfs_trans_commit(
 	 * the dqinfo portion to be.  All that means is that we have some
 	 * (non-persistent) quota reservations that need to be unreserved.
 	 */
-	xfs_trans_unreserve_and_mod_dquots(tp);
+	xfs_trans_unreserve_and_mod_dquots(tp, true);
 	if (tp->t_ticket) {
 		if (regrant && !xlog_is_shutdown(log))
 			xfs_log_ticket_regrant(log, tp->t_ticket);
@@ -1018,7 +1014,7 @@ xfs_trans_cancel(
 	}
 #endif
 	xfs_trans_unreserve_and_mod_sb(tp);
-	xfs_trans_unreserve_and_mod_dquots(tp);
+	xfs_trans_unreserve_and_mod_dquots(tp, false);
 
 	if (tp->t_ticket) {
 		xfs_log_ticket_ungrant(log, tp->t_ticket);

fs/xfs/xfs_trans_dquot.c

@@ -606,6 +606,24 @@ xfs_trans_apply_dquot_deltas(
 			ASSERT(dqp->q_blk.reserved >= dqp->q_blk.count);
 			ASSERT(dqp->q_ino.reserved >= dqp->q_ino.count);
 			ASSERT(dqp->q_rtb.reserved >= dqp->q_rtb.count);
+
+			/*
+			 * We've applied the count changes and given back
+			 * whatever reservation we didn't use.  Zero out the
+			 * dqtrx fields.
+			 */
+			qtrx->qt_blk_res = 0;
+			qtrx->qt_bcount_delta = 0;
+			qtrx->qt_delbcnt_delta = 0;
+
+			qtrx->qt_rtblk_res = 0;
+			qtrx->qt_rtblk_res_used = 0;
+			qtrx->qt_rtbcount_delta = 0;
+			qtrx->qt_delrtb_delta = 0;
+
+			qtrx->qt_ino_res = 0;
+			qtrx->qt_ino_res_used = 0;
+			qtrx->qt_icount_delta = 0;
 		}
 	}
 }
@@ -642,7 +660,8 @@ xfs_trans_unreserve_and_mod_dquots_hook(
  */
 void
 xfs_trans_unreserve_and_mod_dquots(
-	struct xfs_trans	*tp)
+	struct xfs_trans	*tp,
+	bool			already_locked)
 {
 	int			i, j;
 	struct xfs_dquot	*dqp;
@@ -671,10 +690,12 @@ xfs_trans_unreserve_and_mod_dquots(
 			 * about the number of blocks used field, or deltas.
 			 * Also we don't bother to zero the fields.
 			 */
-			locked = false;
+			locked = already_locked;
 			if (qtrx->qt_blk_res) {
-				xfs_dqlock(dqp);
-				locked = true;
+				if (!locked) {
+					xfs_dqlock(dqp);
+					locked = true;
+				}
 				dqp->q_blk.reserved -=
 					(xfs_qcnt_t)qtrx->qt_blk_res;
 			}
@@ -695,7 +716,7 @@ xfs_trans_unreserve_and_mod_dquots(
 				dqp->q_rtb.reserved -=
 					(xfs_qcnt_t)qtrx->qt_rtblk_res;
 			}
-			if (locked)
+			if (locked && !already_locked)
 				xfs_dqunlock(dqp);
 
 		}