quota: Fix rcu annotations of inode dquot pointers

Dquot pointers in i_dquot array in the inode are protected by
dquot_srcu. Annotate the array pointers with __rcu, perform the locked
dereferences with srcu_dereference_check() instead of plain reads, and
set the array elements with rcu_assign_pointer().

Fixes: b9ba6f94b238 ("quota: remove dqptr_sem")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202402061900.rTuYDlo6-lkp@intel.com/
Signed-off-by: Jan Kara <jack@suse.cz>

1 files changed, 39 insertions, 27 deletions

diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index 106800ce1252..22754460fb6f 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -399,7 +399,7 @@ int dquot_mark_dquot_dirty(struct dquot *dquot)
 EXPORT_SYMBOL(dquot_mark_dquot_dirty);
 
 /* Dirtify all the dquots - this can block when journalling */
-static inline int mark_all_dquot_dirty(struct dquot * const *dquots)
+static inline int mark_all_dquot_dirty(struct dquot __rcu * const *dquots)
 {
 	int ret, err, cnt;
 	struct dquot *dquot;
@@ -996,14 +996,15 @@ out:
 }
 EXPORT_SYMBOL(dqget);
 
-static inline struct dquot **i_dquot(struct inode *inode)
+static inline struct dquot __rcu **i_dquot(struct inode *inode)
 {
-	return inode->i_sb->s_op->get_dquots(inode);
+	/* Force __rcu for now until filesystems are fixed */
+	return (struct dquot __rcu **)inode->i_sb->s_op->get_dquots(inode);
 }
 
 static int dqinit_needed(struct inode *inode, int type)
 {
-	struct dquot * const *dquots;
+	struct dquot __rcu * const *dquots;
 	int cnt;
 
 	if (IS_NOQUOTA(inode))
@@ -1093,14 +1094,16 @@ static void remove_dquot_ref(struct super_block *sb, int type)
 		 */
 		spin_lock(&dq_data_lock);
 		if (!IS_NOQUOTA(inode)) {
-			struct dquot **dquots = i_dquot(inode);
-			struct dquot *dquot = dquots[type];
+			struct dquot __rcu **dquots = i_dquot(inode);
+			struct dquot *dquot = srcu_dereference_check(
+				dquots[type], &dquot_srcu,
+				lockdep_is_held(&dq_data_lock));
 
 #ifdef CONFIG_QUOTA_DEBUG
 			if (unlikely(inode_get_rsv_space(inode) > 0))
 				reserved = 1;
 #endif
-			dquots[type] = NULL;
+			rcu_assign_pointer(dquots[type], NULL);
 			if (dquot)
 				dqput(dquot);
 		}
@@ -1453,7 +1456,8 @@ static int inode_quota_active(const struct inode *inode)
 static int __dquot_initialize(struct inode *inode, int type)
 {
 	int cnt, init_needed = 0;
-	struct dquot **dquots, *got[MAXQUOTAS] = {};
+	struct dquot __rcu **dquots;
+	struct dquot *got[MAXQUOTAS] = {};
 	struct super_block *sb = inode->i_sb;
 	qsize_t rsv;
 	int ret = 0;
@@ -1528,7 +1532,7 @@ static int __dquot_initialize(struct inode *inode, int type)
 		if (!got[cnt])
 			continue;
 		if (!dquots[cnt]) {
-			dquots[cnt] = got[cnt];
+			rcu_assign_pointer(dquots[cnt], got[cnt]);
 			got[cnt] = NULL;
 			/*
 			 * Make quota reservation system happy if someone
@@ -1536,12 +1540,16 @@ static int __dquot_initialize(struct inode *inode, int type)
 			 */
 			rsv = inode_get_rsv_space(inode);
 			if (unlikely(rsv)) {
+				struct dquot *dquot = srcu_dereference_check(
+					dquots[cnt], &dquot_srcu,
+					lockdep_is_held(&dq_data_lock));
+
 				spin_lock(&inode->i_lock);
 				/* Get reservation again under proper lock */
 				rsv = __inode_get_rsv_space(inode);
-				spin_lock(&dquots[cnt]->dq_dqb_lock);
-				dquots[cnt]->dq_dqb.dqb_rsvspace += rsv;
-				spin_unlock(&dquots[cnt]->dq_dqb_lock);
+				spin_lock(&dquot->dq_dqb_lock);
+				dquot->dq_dqb.dqb_rsvspace += rsv;
+				spin_unlock(&dquot->dq_dqb_lock);
 				spin_unlock(&inode->i_lock);
 			}
 		}
@@ -1563,7 +1571,7 @@ EXPORT_SYMBOL(dquot_initialize);
 
 bool dquot_initialize_needed(struct inode *inode)
 {
-	struct dquot **dquots;
+	struct dquot __rcu **dquots;
 	int i;
 
 	if (!inode_quota_active(inode))
@@ -1588,13 +1596,14 @@ EXPORT_SYMBOL(dquot_initialize_needed);
 static void __dquot_drop(struct inode *inode)
 {
 	int cnt;
-	struct dquot **dquots = i_dquot(inode);
+	struct dquot __rcu **dquots = i_dquot(inode);
 	struct dquot *put[MAXQUOTAS];
 
 	spin_lock(&dq_data_lock);
 	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
-		put[cnt] = dquots[cnt];
-		dquots[cnt] = NULL;
+		put[cnt] = srcu_dereference_check(dquots[cnt], &dquot_srcu,
+					lockdep_is_held(&dq_data_lock));
+		rcu_assign_pointer(dquots[cnt], NULL);
 	}
 	spin_unlock(&dq_data_lock);
 	dqput_all(put);
@@ -1602,7 +1611,7 @@ static void __dquot_drop(struct inode *inode)
 
 void dquot_drop(struct inode *inode)
 {
-	struct dquot * const *dquots;
+	struct dquot __rcu * const *dquots;
 	int cnt;
 
 	if (IS_NOQUOTA(inode))
@@ -1675,7 +1684,7 @@ int __dquot_alloc_space(struct inode *inode, qsize_t number, int flags)
 	int cnt, ret = 0, index;
 	struct dquot_warn warn[MAXQUOTAS];
 	int reserve = flags & DQUOT_SPACE_RESERVE;
-	struct dquot **dquots;
+	struct dquot __rcu **dquots;
 	struct dquot *dquot;
 
 	if (!inode_quota_active(inode)) {
@@ -1745,7 +1754,7 @@ int dquot_alloc_inode(struct inode *inode)
 {
 	int cnt, ret = 0, index;
 	struct dquot_warn warn[MAXQUOTAS];
-	struct dquot * const *dquots;
+	struct dquot __rcu * const *dquots;
 	struct dquot *dquot;
 
 	if (!inode_quota_active(inode))
@@ -1790,7 +1799,7 @@ EXPORT_SYMBOL(dquot_alloc_inode);
  */
 void dquot_claim_space_nodirty(struct inode *inode, qsize_t number)
 {
-	struct dquot **dquots;
+	struct dquot __rcu **dquots;
 	struct dquot *dquot;
 	int cnt, index;
 
@@ -1832,7 +1841,7 @@ EXPORT_SYMBOL(dquot_claim_space_nodirty);
  */
 void dquot_reclaim_space_nodirty(struct inode *inode, qsize_t number)
 {
-	struct dquot **dquots;
+	struct dquot __rcu **dquots;
 	struct dquot *dquot;
 	int cnt, index;
 
@@ -1876,7 +1885,7 @@ void __dquot_free_space(struct inode *inode, qsize_t number, int flags)
 {
 	unsigned int cnt;
 	struct dquot_warn warn[MAXQUOTAS];
-	struct dquot **dquots;
+	struct dquot __rcu **dquots;
 	struct dquot *dquot;
 	int reserve = flags & DQUOT_SPACE_RESERVE, index;
 
@@ -1933,7 +1942,7 @@ void dquot_free_inode(struct inode *inode)
 {
 	unsigned int cnt;
 	struct dquot_warn warn[MAXQUOTAS];
-	struct dquot * const *dquots;
+	struct dquot __rcu * const *dquots;
 	struct dquot *dquot;
 	int index;
 
@@ -1980,6 +1989,7 @@ int __dquot_transfer(struct inode *inode, struct dquot **transfer_to)
 	qsize_t cur_space;
 	qsize_t rsv_space = 0;
 	qsize_t inode_usage = 1;
+	struct dquot __rcu **dquots;
 	struct dquot *transfer_from[MAXQUOTAS] = {};
 	int cnt, index, ret = 0;
 	char is_valid[MAXQUOTAS] = {};
@@ -2012,6 +2022,7 @@ int __dquot_transfer(struct inode *inode, struct dquot **transfer_to)
 	}
 	cur_space = __inode_get_bytes(inode);
 	rsv_space = __inode_get_rsv_space(inode);
+	dquots = i_dquot(inode);
 	/*
 	 * Build the transfer_from list, check limits, and update usage in
 	 * the target structures.
@@ -2026,7 +2037,8 @@ int __dquot_transfer(struct inode *inode, struct dquot **transfer_to)
 		if (!sb_has_quota_active(inode->i_sb, cnt))
 			continue;
 		is_valid[cnt] = 1;
-		transfer_from[cnt] = i_dquot(inode)[cnt];
+		transfer_from[cnt] = srcu_dereference_check(dquots[cnt],
+				&dquot_srcu, lockdep_is_held(&dq_data_lock));
 		ret = dquot_add_inodes(transfer_to[cnt], inode_usage,
 				       &warn_to[cnt]);
 		if (ret)
@@ -2065,7 +2077,7 @@ int __dquot_transfer(struct inode *inode, struct dquot **transfer_to)
 						  rsv_space);
 			spin_unlock(&transfer_from[cnt]->dq_dqb_lock);
 		}
-		i_dquot(inode)[cnt] = transfer_to[cnt];
+		rcu_assign_pointer(dquots[cnt], transfer_to[cnt]);
 	}
 	spin_unlock(&inode->i_lock);
 	spin_unlock(&dq_data_lock);
@@ -2076,8 +2088,8 @@ int __dquot_transfer(struct inode *inode, struct dquot **transfer_to)
 	 * mark_all_dquot_dirty().
 	 */
 	index = srcu_read_lock(&dquot_srcu);
-	mark_all_dquot_dirty(transfer_from);
-	mark_all_dquot_dirty(transfer_to);
+	mark_all_dquot_dirty((struct dquot __rcu **)transfer_from);
+	mark_all_dquot_dirty((struct dquot __rcu **)transfer_to);
 	srcu_read_unlock(&dquot_srcu, index);
 
 	flush_warnings(warn_to);