1 files changed, 322 insertions, 241 deletions

diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index dc5f8654b277..a7ddb874912d 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -223,18 +223,26 @@ static void put_quota_format(struct quota_format_type *fmt)
 
 /*
  * Dquot List Management:
- * The quota code uses four lists for dquot management: the inuse_list,
- * free_dquots, dqi_dirty_list, and dquot_hash[] array. A single dquot
- * structure may be on some of those lists, depending on its current state.
+ * The quota code uses five lists for dquot management: the inuse_list,
+ * releasing_dquots, free_dquots, dqi_dirty_list, and dquot_hash[] array.
+ * A single dquot structure may be on some of those lists, depending on
+ * its current state.
  *
  * All dquots are placed to the end of inuse_list when first created, and this
  * list is used for invalidate operation, which must look at every dquot.
  *
- * Unused dquots (dq_count == 0) are added to the free_dquots list when freed,
- * and this list is searched whenever we need an available dquot.  Dquots are
- * removed from the list as soon as they are used again, and
- * dqstats.free_dquots gives the number of dquots on the list. When
- * dquot is invalidated it's completely released from memory.
+ * When the last reference of a dquot is dropped, the dquot is added to
+ * releasing_dquots. We'll then queue work item which will call
+ * synchronize_srcu() and after that perform the final cleanup of all the
+ * dquots on the list. Each cleaned up dquot is moved to free_dquots list.
+ * Both releasing_dquots and free_dquots use the dq_free list_head in the dquot
+ * struct.
+ *
+ * Unused and cleaned up dquots are in the free_dquots list and this list is
+ * searched whenever we need an available dquot. Dquots are removed from the
+ * list as soon as they are used again and dqstats.free_dquots gives the number
+ * of dquots on the list. When dquot is invalidated it's completely released
+ * from memory.
  *
  * Dirty dquots are added to the dqi_dirty_list of quota_info when mark
  * dirtied, and this list is searched when writing dirty dquots back to
@@ -248,6 +256,7 @@ static void put_quota_format(struct quota_format_type *fmt)
 
 static LIST_HEAD(inuse_list);
 static LIST_HEAD(free_dquots);
+static LIST_HEAD(releasing_dquots);
 static unsigned int dq_hash_bits, dq_hash_mask;
 static struct hlist_head *dquot_hash;
 
@@ -258,6 +267,9 @@ static qsize_t inode_get_rsv_space(struct inode *inode);
 static qsize_t __inode_get_rsv_space(struct inode *inode);
 static int __dquot_initialize(struct inode *inode, int type);
 
+static void quota_release_workfn(struct work_struct *work);
+static DECLARE_DELAYED_WORK(quota_release_work, quota_release_workfn);
+
 static inline unsigned int
 hashfn(const struct super_block *sb, struct kqid qid)
 {
@@ -305,12 +317,21 @@ static inline void put_dquot_last(struct dquot *dquot)
 	dqstats_inc(DQST_FREE_DQUOTS);
 }
 
+static inline void put_releasing_dquots(struct dquot *dquot)
+{
+	list_add_tail(&dquot->dq_free, &releasing_dquots);
+	set_bit(DQ_RELEASING_B, &dquot->dq_flags);
+}
+
 static inline void remove_free_dquot(struct dquot *dquot)
 {
 	if (list_empty(&dquot->dq_free))
 		return;
 	list_del_init(&dquot->dq_free);
-	dqstats_dec(DQST_FREE_DQUOTS);
+	if (!test_bit(DQ_RELEASING_B, &dquot->dq_flags))
+		dqstats_dec(DQST_FREE_DQUOTS);
+	else
+		clear_bit(DQ_RELEASING_B, &dquot->dq_flags);
 }
 
 static inline void put_inuse(struct dquot *dquot)
@@ -336,6 +357,11 @@ static void wait_on_dquot(struct dquot *dquot)
 	mutex_unlock(&dquot->dq_lock);
 }
 
+static inline int dquot_active(struct dquot *dquot)
+{
+	return test_bit(DQ_ACTIVE_B, &dquot->dq_flags);
+}
+
 static inline int dquot_dirty(struct dquot *dquot)
 {
 	return test_bit(DQ_MOD_B, &dquot->dq_flags);
@@ -351,14 +377,14 @@ int dquot_mark_dquot_dirty(struct dquot *dquot)
 {
 	int ret = 1;
 
-	if (!test_bit(DQ_ACTIVE_B, &dquot->dq_flags))
+	if (!dquot_active(dquot))
 		return 0;
 
 	if (sb_dqopt(dquot->dq_sb)->flags & DQUOT_NOLIST_DIRTY)
 		return test_and_set_bit(DQ_MOD_B, &dquot->dq_flags);
 
 	/* If quota is dirty already, we don't have to acquire dq_list_lock */
-	if (test_bit(DQ_MOD_B, &dquot->dq_flags))
+	if (dquot_dirty(dquot))
 		return 1;
 
 	spin_lock(&dq_list_lock);
@@ -373,15 +399,17 @@ 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 *dquot)
+static inline int mark_all_dquot_dirty(struct dquot __rcu * const *dquots)
 {
 	int ret, err, cnt;
+	struct dquot *dquot;
 
 	ret = err = 0;
 	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
-		if (dquot[cnt])
+		dquot = srcu_dereference(dquots[cnt], &dquot_srcu);
+		if (dquot)
 			/* Even in case of error we have to continue */
-			ret = mark_dquot_dirty(dquot[cnt]);
+			ret = mark_dquot_dirty(dquot);
 		if (!err)
 			err = ret;
 	}
@@ -438,7 +466,7 @@ int dquot_acquire(struct dquot *dquot)
 	smp_mb__before_atomic();
 	set_bit(DQ_READ_B, &dquot->dq_flags);
 	/* Instantiate dquot if needed */
-	if (!test_bit(DQ_ACTIVE_B, &dquot->dq_flags) && !dquot->dq_off) {
+	if (!dquot_active(dquot) && !dquot->dq_off) {
 		ret = dqopt->ops[dquot->dq_id.type]->commit_dqblk(dquot);
 		/* Write the info if needed */
 		if (info_dirty(&dqopt->info[dquot->dq_id.type])) {
@@ -477,7 +505,7 @@ int dquot_commit(struct dquot *dquot)
 		goto out_lock;
 	/* Inactive dquot can be only if there was error during read/init
 	 * => we have better not writing it */
-	if (test_bit(DQ_ACTIVE_B, &dquot->dq_flags))
+	if (dquot_active(dquot))
 		ret = dqopt->ops[dquot->dq_id.type]->commit_dqblk(dquot);
 	else
 		ret = -EIO;
@@ -538,6 +566,8 @@ static void invalidate_dquots(struct super_block *sb, int type)
 	struct dquot *dquot, *tmp;
 
 restart:
+	flush_delayed_work(&quota_release_work);
+
 	spin_lock(&dq_list_lock);
 	list_for_each_entry_safe(dquot, tmp, &inuse_list, dq_inuse) {
 		if (dquot->dq_sb != sb)
@@ -546,7 +576,7 @@ restart:
 			continue;
 		/* Wait for dquot users */
 		if (atomic_read(&dquot->dq_count)) {
-			dqgrab(dquot);
+			atomic_inc(&dquot->dq_count);
 			spin_unlock(&dq_list_lock);
 			/*
 			 * Once dqput() wakes us up, we know it's time to free
@@ -565,6 +595,15 @@ restart:
 			goto restart;
 		}
 		/*
+		 * The last user already dropped its reference but dquot didn't
+		 * get fully cleaned up yet. Restart the scan which flushes the
+		 * work cleaning up released dquots.
+		 */
+		if (test_bit(DQ_RELEASING_B, &dquot->dq_flags)) {
+			spin_unlock(&dq_list_lock);
+			goto restart;
+		}
+		/*
 		 * Quota now has no users and it has been written on last
 		 * dqput()
 		 */
@@ -588,14 +627,13 @@ int dquot_scan_active(struct super_block *sb,
 
 	spin_lock(&dq_list_lock);
 	list_for_each_entry(dquot, &inuse_list, dq_inuse) {
-		if (!test_bit(DQ_ACTIVE_B, &dquot->dq_flags))
+		if (!dquot_active(dquot))
 			continue;
 		if (dquot->dq_sb != sb)
 			continue;
 		/* Now we have active dquot so we can just increase use count */
 		atomic_inc(&dquot->dq_count);
 		spin_unlock(&dq_list_lock);
-		dqstats_inc(DQST_LOOKUPS);
 		dqput(old_dquot);
 		old_dquot = dquot;
 		/*
@@ -604,7 +642,7 @@ int dquot_scan_active(struct super_block *sb,
 		 * outstanding call and recheck the DQ_ACTIVE_B after that.
 		 */
 		wait_on_dquot(dquot);
-		if (test_bit(DQ_ACTIVE_B, &dquot->dq_flags)) {
+		if (dquot_active(dquot)) {
 			ret = fn(dquot, priv);
 			if (ret < 0)
 				goto out;
@@ -620,6 +658,18 @@ out:
 }
 EXPORT_SYMBOL(dquot_scan_active);
 
+static inline int dquot_write_dquot(struct dquot *dquot)
+{
+	int ret = dquot->dq_sb->dq_op->write_dquot(dquot);
+	if (ret < 0) {
+		quota_error(dquot->dq_sb, "Can't write quota structure "
+			    "(error %d). Quota may get out of sync!", ret);
+		/* Clear dirty bit anyway to avoid infinite loop. */
+		clear_dquot_dirty(dquot);
+	}
+	return ret;
+}
+
 /* Write all dquot structures to quota files */
 int dquot_writeback_dquots(struct super_block *sb, int type)
 {
@@ -643,24 +693,23 @@ int dquot_writeback_dquots(struct super_block *sb, int type)
 			dquot = list_first_entry(&dirty, struct dquot,
 						 dq_dirty);
 
-			WARN_ON(!test_bit(DQ_ACTIVE_B, &dquot->dq_flags));
+			WARN_ON(!dquot_active(dquot));
+			/* If the dquot is releasing we should not touch it */
+			if (test_bit(DQ_RELEASING_B, &dquot->dq_flags)) {
+				spin_unlock(&dq_list_lock);
+				flush_delayed_work(&quota_release_work);
+				spin_lock(&dq_list_lock);
+				continue;
+			}
 
 			/* Now we have active dquot from which someone is
  			 * holding reference so we can safely just increase
 			 * use count */
 			dqgrab(dquot);
 			spin_unlock(&dq_list_lock);
-			dqstats_inc(DQST_LOOKUPS);
-			err = sb->dq_op->write_dquot(dquot);
-			if (err) {
-				/*
-				 * Clear dirty bit anyway to avoid infinite
-				 * loop here.
-				 */
-				clear_dquot_dirty(dquot);
-				if (!ret)
-					ret = err;
-			}
+			err = dquot_write_dquot(dquot);
+			if (err && !ret)
+				ret = err;
 			dqput(dquot);
 			spin_lock(&dq_list_lock);
 		}
@@ -754,12 +803,52 @@ static struct shrinker dqcache_shrinker = {
 };
 
 /*
+ * Safely release dquot and put reference to dquot.
+ */
+static void quota_release_workfn(struct work_struct *work)
+{
+	struct dquot *dquot;
+	struct list_head rls_head;
+
+	spin_lock(&dq_list_lock);
+	/* Exchange the list head to avoid livelock. */
+	list_replace_init(&releasing_dquots, &rls_head);
+	spin_unlock(&dq_list_lock);
+	synchronize_srcu(&dquot_srcu);
+
+restart:
+	spin_lock(&dq_list_lock);
+	while (!list_empty(&rls_head)) {
+		dquot = list_first_entry(&rls_head, struct dquot, dq_free);
+		WARN_ON_ONCE(atomic_read(&dquot->dq_count));
+		/*
+		 * Note that DQ_RELEASING_B protects us from racing with
+		 * invalidate_dquots() calls so we are safe to work with the
+		 * dquot even after we drop dq_list_lock.
+		 */
+		if (dquot_dirty(dquot)) {
+			spin_unlock(&dq_list_lock);
+			/* Commit dquot before releasing */
+			dquot_write_dquot(dquot);
+			goto restart;
+		}
+		if (dquot_active(dquot)) {
+			spin_unlock(&dq_list_lock);
+			dquot->dq_sb->dq_op->release_dquot(dquot);
+			goto restart;
+		}
+		/* Dquot is inactive and clean, now move it to free list */
+		remove_free_dquot(dquot);
+		put_dquot_last(dquot);
+	}
+	spin_unlock(&dq_list_lock);
+}
+
+/*
  * Put reference to dquot
  */
 void dqput(struct dquot *dquot)
 {
-	int ret;
-
 	if (!dquot)
 		return;
 #ifdef CONFIG_QUOTA_DEBUG
@@ -771,7 +860,7 @@ void dqput(struct dquot *dquot)
 	}
 #endif
 	dqstats_inc(DQST_DROPS);
-we_slept:
+
 	spin_lock(&dq_list_lock);
 	if (atomic_read(&dquot->dq_count) > 1) {
 		/* We have more than one user... nothing to do */
@@ -783,35 +872,16 @@ we_slept:
 		spin_unlock(&dq_list_lock);
 		return;
 	}
+
 	/* Need to release dquot? */
-	if (dquot_dirty(dquot)) {
-		spin_unlock(&dq_list_lock);
-		/* Commit dquot before releasing */
-		ret = dquot->dq_sb->dq_op->write_dquot(dquot);
-		if (ret < 0) {
-			quota_error(dquot->dq_sb, "Can't write quota structure"
-				    " (error %d). Quota may get out of sync!",
-				    ret);
-			/*
-			 * We clear dirty bit anyway, so that we avoid
-			 * infinite loop here
-			 */
-			clear_dquot_dirty(dquot);
-		}
-		goto we_slept;
-	}
-	if (test_bit(DQ_ACTIVE_B, &dquot->dq_flags)) {
-		spin_unlock(&dq_list_lock);
-		dquot->dq_sb->dq_op->release_dquot(dquot);
-		goto we_slept;
-	}
-	atomic_dec(&dquot->dq_count);
 #ifdef CONFIG_QUOTA_DEBUG
 	/* sanity check */
 	BUG_ON(!list_empty(&dquot->dq_free));
 #endif
-	put_dquot_last(dquot);
+	put_releasing_dquots(dquot);
+	atomic_dec(&dquot->dq_count);
 	spin_unlock(&dq_list_lock);
+	queue_delayed_work(system_unbound_wq, &quota_release_work, 1);
 }
 EXPORT_SYMBOL(dqput);
 
@@ -898,10 +968,10 @@ we_slept:
 		dqstats_inc(DQST_LOOKUPS);
 	}
 	/* Wait for dq_lock - after this we know that either dquot_release() is
-	 * already finished or it will be canceled due to dq_count > 1 test */
+	 * already finished or it will be canceled due to dq_count > 0 test */
 	wait_on_dquot(dquot);
 	/* Read the dquot / allocate space in quota file */
-	if (!test_bit(DQ_ACTIVE_B, &dquot->dq_flags)) {
+	if (!dquot_active(dquot)) {
 		int err;
 
 		err = sb->dq_op->acquire_dquot(dquot);
@@ -927,14 +997,15 @@ 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))
@@ -1007,59 +1078,7 @@ out:
 	return err;
 }
 
-/*
- * Remove references to dquots from inode and add dquot to list for freeing
- * if we have the last reference to dquot
- */
-static void remove_inode_dquot_ref(struct inode *inode, int type,
-				   struct list_head *tofree_head)
-{
-	struct dquot **dquots = i_dquot(inode);
-	struct dquot *dquot = dquots[type];
-
-	if (!dquot)
-		return;
-
-	dquots[type] = NULL;
-	if (list_empty(&dquot->dq_free)) {
-		/*
-		 * The inode still has reference to dquot so it can't be in the
-		 * free list
-		 */
-		spin_lock(&dq_list_lock);
-		list_add(&dquot->dq_free, tofree_head);
-		spin_unlock(&dq_list_lock);
-	} else {
-		/*
-		 * Dquot is already in a list to put so we won't drop the last
-		 * reference here.
-		 */
-		dqput(dquot);
-	}
-}
-
-/*
- * Free list of dquots
- * Dquots are removed from inodes and no new references can be got so we are
- * the only ones holding reference
- */
-static void put_dquot_list(struct list_head *tofree_head)
-{
-	struct list_head *act_head;
-	struct dquot *dquot;
-
-	act_head = tofree_head->next;
-	while (act_head != tofree_head) {
-		dquot = list_entry(act_head, struct dquot, dq_free);
-		act_head = act_head->next;
-		/* Remove dquot from the list so we won't have problems... */
-		list_del_init(&dquot->dq_free);
-		dqput(dquot);
-	}
-}
-
-static void remove_dquot_ref(struct super_block *sb, int type,
-		struct list_head *tofree_head)
+static void remove_dquot_ref(struct super_block *sb, int type)
 {
 	struct inode *inode;
 #ifdef CONFIG_QUOTA_DEBUG
@@ -1076,11 +1095,18 @@ static void remove_dquot_ref(struct super_block *sb, int type,
 		 */
 		spin_lock(&dq_data_lock);
 		if (!IS_NOQUOTA(inode)) {
+			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
-			remove_inode_dquot_ref(inode, type, tofree_head);
+			rcu_assign_pointer(dquots[type], NULL);
+			if (dquot)
+				dqput(dquot);
 		}
 		spin_unlock(&dq_data_lock);
 	}
@@ -1097,13 +1123,8 @@ static void remove_dquot_ref(struct super_block *sb, int type,
 /* Gather all references from inodes and drop them */
 static void drop_dquot_ref(struct super_block *sb, int type)
 {
-	LIST_HEAD(tofree_head);
-
-	if (sb->dq_op) {
-		remove_dquot_ref(sb, type, &tofree_head);
-		synchronize_srcu(&dquot_srcu);
-		put_dquot_list(&tofree_head);
-	}
+	if (sb->dq_op)
+		remove_dquot_ref(sb, type);
 }
 
 static inline
@@ -1418,7 +1439,7 @@ static int info_bdq_free(struct dquot *dquot, qsize_t space)
 	return QUOTA_NL_NOWARN;
 }
 
-static int dquot_active(const struct inode *inode)
+static int inode_quota_active(const struct inode *inode)
 {
 	struct super_block *sb = inode->i_sb;
 
@@ -1436,12 +1457,13 @@ static int dquot_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;
 
-	if (!dquot_active(inode))
+	if (!inode_quota_active(inode))
 		return 0;
 
 	dquots = i_dquot(inode);
@@ -1511,7 +1533,7 @@ 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
@@ -1519,12 +1541,16 @@ 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);
 			}
 		}
@@ -1546,10 +1572,10 @@ EXPORT_SYMBOL(dquot_initialize);
 
 bool dquot_initialize_needed(struct inode *inode)
 {
-	struct dquot **dquots;
+	struct dquot __rcu **dquots;
 	int i;
 
-	if (!dquot_active(inode))
+	if (!inode_quota_active(inode))
 		return false;
 
 	dquots = i_dquot(inode);
@@ -1571,13 +1597,14 @@ 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);
@@ -1585,7 +1612,7 @@ 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))
@@ -1658,9 +1685,10 @@ 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 (!dquot_active(inode)) {
+	if (!inode_quota_active(inode)) {
 		if (reserve) {
 			spin_lock(&inode->i_lock);
 			*inode_reserved_space(inode) += number;
@@ -1678,27 +1706,26 @@ int __dquot_alloc_space(struct inode *inode, qsize_t number, int flags)
 	index = srcu_read_lock(&dquot_srcu);
 	spin_lock(&inode->i_lock);
 	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
-		if (!dquots[cnt])
+		dquot = srcu_dereference(dquots[cnt], &dquot_srcu);
+		if (!dquot)
 			continue;
 		if (reserve) {
-			ret = dquot_add_space(dquots[cnt], 0, number, flags,
-					      &warn[cnt]);
+			ret = dquot_add_space(dquot, 0, number, flags, &warn[cnt]);
 		} else {
-			ret = dquot_add_space(dquots[cnt], number, 0, flags,
-					      &warn[cnt]);
+			ret = dquot_add_space(dquot, number, 0, flags, &warn[cnt]);
 		}
 		if (ret) {
 			/* Back out changes we already did */
 			for (cnt--; cnt >= 0; cnt--) {
-				if (!dquots[cnt])
+				dquot = srcu_dereference(dquots[cnt], &dquot_srcu);
+				if (!dquot)
 					continue;
-				spin_lock(&dquots[cnt]->dq_dqb_lock);
+				spin_lock(&dquot->dq_dqb_lock);
 				if (reserve)
-					dquot_free_reserved_space(dquots[cnt],
-								  number);
+					dquot_free_reserved_space(dquot, number);
 				else
-					dquot_decr_space(dquots[cnt], number);
-				spin_unlock(&dquots[cnt]->dq_dqb_lock);
+					dquot_decr_space(dquot, number);
+				spin_unlock(&dquot->dq_dqb_lock);
 			}
 			spin_unlock(&inode->i_lock);
 			goto out_flush_warn;
@@ -1728,9 +1755,10 @@ 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 (!dquot_active(inode))
+	if (!inode_quota_active(inode))
 		return 0;
 	for (cnt = 0; cnt < MAXQUOTAS; cnt++)
 		warn[cnt].w_type = QUOTA_NL_NOWARN;
@@ -1739,17 +1767,19 @@ int dquot_alloc_inode(struct inode *inode)
 	index = srcu_read_lock(&dquot_srcu);
 	spin_lock(&inode->i_lock);
 	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
-		if (!dquots[cnt])
+		dquot = srcu_dereference(dquots[cnt], &dquot_srcu);
+		if (!dquot)
 			continue;
-		ret = dquot_add_inodes(dquots[cnt], 1, &warn[cnt]);
+		ret = dquot_add_inodes(dquot, 1, &warn[cnt]);
 		if (ret) {
 			for (cnt--; cnt >= 0; cnt--) {
-				if (!dquots[cnt])
+				dquot = srcu_dereference(dquots[cnt], &dquot_srcu);
+				if (!dquot)
 					continue;
 				/* Back out changes we already did */
-				spin_lock(&dquots[cnt]->dq_dqb_lock);
-				dquot_decr_inodes(dquots[cnt], 1);
-				spin_unlock(&dquots[cnt]->dq_dqb_lock);
+				spin_lock(&dquot->dq_dqb_lock);
+				dquot_decr_inodes(dquot, 1);
+				spin_unlock(&dquot->dq_dqb_lock);
 			}
 			goto warn_put_all;
 		}
@@ -1770,10 +1800,11 @@ EXPORT_SYMBOL(dquot_alloc_inode);
  */
 int dquot_claim_space_nodirty(struct inode *inode, qsize_t number)
 {
-	struct dquot **dquots;
+	struct dquot __rcu **dquots;
+	struct dquot *dquot;
 	int cnt, index;
 
-	if (!dquot_active(inode)) {
+	if (!inode_quota_active(inode)) {
 		spin_lock(&inode->i_lock);
 		*inode_reserved_space(inode) -= number;
 		__inode_add_bytes(inode, number);
@@ -1786,9 +1817,8 @@ int dquot_claim_space_nodirty(struct inode *inode, qsize_t number)
 	spin_lock(&inode->i_lock);
 	/* Claim reserved quotas to allocated quotas */
 	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
-		if (dquots[cnt]) {
-			struct dquot *dquot = dquots[cnt];
-
+		dquot = srcu_dereference(dquots[cnt], &dquot_srcu);
+		if (dquot) {
 			spin_lock(&dquot->dq_dqb_lock);
 			if (WARN_ON_ONCE(dquot->dq_dqb.dqb_rsvspace < number))
 				number = dquot->dq_dqb.dqb_rsvspace;
@@ -1812,10 +1842,11 @@ 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;
 
-	if (!dquot_active(inode)) {
+	if (!inode_quota_active(inode)) {
 		spin_lock(&inode->i_lock);
 		*inode_reserved_space(inode) += number;
 		__inode_sub_bytes(inode, number);
@@ -1828,9 +1859,8 @@ void dquot_reclaim_space_nodirty(struct inode *inode, qsize_t number)
 	spin_lock(&inode->i_lock);
 	/* Claim reserved quotas to allocated quotas */
 	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
-		if (dquots[cnt]) {
-			struct dquot *dquot = dquots[cnt];
-
+		dquot = srcu_dereference(dquots[cnt], &dquot_srcu);
+		if (dquot) {
 			spin_lock(&dquot->dq_dqb_lock);
 			if (WARN_ON_ONCE(dquot->dq_dqb.dqb_curspace < number))
 				number = dquot->dq_dqb.dqb_curspace;
@@ -1856,10 +1886,11 @@ 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;
 
-	if (!dquot_active(inode)) {
+	if (!inode_quota_active(inode)) {
 		if (reserve) {
 			spin_lock(&inode->i_lock);
 			*inode_reserved_space(inode) -= number;
@@ -1877,17 +1908,18 @@ void __dquot_free_space(struct inode *inode, qsize_t number, int flags)
 		int wtype;
 
 		warn[cnt].w_type = QUOTA_NL_NOWARN;
-		if (!dquots[cnt])
+		dquot = srcu_dereference(dquots[cnt], &dquot_srcu);
+		if (!dquot)
 			continue;
-		spin_lock(&dquots[cnt]->dq_dqb_lock);
-		wtype = info_bdq_free(dquots[cnt], number);
+		spin_lock(&dquot->dq_dqb_lock);
+		wtype = info_bdq_free(dquot, number);
 		if (wtype != QUOTA_NL_NOWARN)
-			prepare_warning(&warn[cnt], dquots[cnt], wtype);
+			prepare_warning(&warn[cnt], dquot, wtype);
 		if (reserve)
-			dquot_free_reserved_space(dquots[cnt], number);
+			dquot_free_reserved_space(dquot, number);
 		else
-			dquot_decr_space(dquots[cnt], number);
-		spin_unlock(&dquots[cnt]->dq_dqb_lock);
+			dquot_decr_space(dquot, number);
+		spin_unlock(&dquot->dq_dqb_lock);
 	}
 	if (reserve)
 		*inode_reserved_space(inode) -= number;
@@ -1911,10 +1943,11 @@ 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;
 
-	if (!dquot_active(inode))
+	if (!inode_quota_active(inode))
 		return;
 
 	dquots = i_dquot(inode);
@@ -1922,16 +1955,16 @@ void dquot_free_inode(struct inode *inode)
 	spin_lock(&inode->i_lock);
 	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
 		int wtype;
-
 		warn[cnt].w_type = QUOTA_NL_NOWARN;
-		if (!dquots[cnt])
+		dquot = srcu_dereference(dquots[cnt], &dquot_srcu);
+		if (!dquot)
 			continue;
-		spin_lock(&dquots[cnt]->dq_dqb_lock);
-		wtype = info_idq_free(dquots[cnt], 1);
+		spin_lock(&dquot->dq_dqb_lock);
+		wtype = info_idq_free(dquot, 1);
 		if (wtype != QUOTA_NL_NOWARN)
-			prepare_warning(&warn[cnt], dquots[cnt], wtype);
-		dquot_decr_inodes(dquots[cnt], 1);
-		spin_unlock(&dquots[cnt]->dq_dqb_lock);
+			prepare_warning(&warn[cnt], dquot, wtype);
+		dquot_decr_inodes(dquot, 1);
+		spin_unlock(&dquot->dq_dqb_lock);
 	}
 	spin_unlock(&inode->i_lock);
 	mark_all_dquot_dirty(dquots);
@@ -1957,8 +1990,9 @@ 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, ret = 0;
+	int cnt, index, ret = 0;
 	char is_valid[MAXQUOTAS] = {};
 	struct dquot_warn warn_to[MAXQUOTAS];
 	struct dquot_warn warn_from_inodes[MAXQUOTAS];
@@ -1989,6 +2023,7 @@ 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.
@@ -2003,7 +2038,8 @@ 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)
@@ -2042,13 +2078,21 @@ 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);
 
-	mark_all_dquot_dirty(transfer_from);
-	mark_all_dquot_dirty(transfer_to);
+	/*
+	 * These arrays are local and we hold dquot references so we don't need
+	 * the srcu protection but still take dquot_srcu to avoid warning in
+	 * mark_all_dquot_dirty().
+	 */
+	index = srcu_read_lock(&dquot_srcu);
+	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);
 	flush_warnings(warn_from_inodes);
 	flush_warnings(warn_from_space);
@@ -2085,7 +2129,7 @@ int dquot_transfer(struct inode *inode, struct iattr *iattr)
 	struct super_block *sb = inode->i_sb;
 	int ret;
 
-	if (!dquot_active(inode))
+	if (!inode_quota_active(inode))
 		return 0;
 
 	if (iattr->ia_valid & ATTR_UID && !uid_eq(iattr->ia_uid, inode->i_uid)){
@@ -2306,28 +2350,76 @@ EXPORT_SYMBOL(dquot_quota_off);
  *	Turn quotas on on a device
  */
 
-/*
- * Helper function to turn quotas on when we already have the inode of
- * quota file and no quota information is loaded.
- */
-static int vfs_load_quota_inode(struct inode *inode, int type, int format_id,
+static int vfs_setup_quota_inode(struct inode *inode, int type)
+{
+	struct super_block *sb = inode->i_sb;
+	struct quota_info *dqopt = sb_dqopt(sb);
+
+	if (is_bad_inode(inode))
+		return -EUCLEAN;
+	if (!S_ISREG(inode->i_mode))
+		return -EACCES;
+	if (IS_RDONLY(inode))
+		return -EROFS;
+	if (sb_has_quota_loaded(sb, type))
+		return -EBUSY;
+
+	/*
+	 * Quota files should never be encrypted.  They should be thought of as
+	 * filesystem metadata, not user data.  New-style internal quota files
+	 * cannot be encrypted by users anyway, but old-style external quota
+	 * files could potentially be incorrectly created in an encrypted
+	 * directory, hence this explicit check.  Some reasons why encrypted
+	 * quota files don't work include: (1) some filesystems that support
+	 * encryption don't handle it in their quota_read and quota_write, and
+	 * (2) cleaning up encrypted quota files at unmount would need special
+	 * consideration, as quota files are cleaned up later than user files.
+	 */
+	if (IS_ENCRYPTED(inode))
+		return -EINVAL;
+
+	dqopt->files[type] = igrab(inode);
+	if (!dqopt->files[type])
+		return -EIO;
+	if (!(dqopt->flags & DQUOT_QUOTA_SYS_FILE)) {
+		/* We don't want quota and atime on quota files (deadlocks
+		 * possible) Also nobody should write to the file - we use
+		 * special IO operations which ignore the immutable bit. */
+		inode_lock(inode);
+		inode->i_flags |= S_NOQUOTA;
+		inode_unlock(inode);
+		/*
+		 * When S_NOQUOTA is set, remove dquot references as no more
+		 * references can be added
+		 */
+		__dquot_drop(inode);
+	}
+	return 0;
+}
+
+static void vfs_cleanup_quota_inode(struct super_block *sb, int type)
+{
+	struct quota_info *dqopt = sb_dqopt(sb);
+	struct inode *inode = dqopt->files[type];
+
+	if (!(dqopt->flags & DQUOT_QUOTA_SYS_FILE)) {
+		inode_lock(inode);
+		inode->i_flags &= ~S_NOQUOTA;
+		inode_unlock(inode);
+	}
+	dqopt->files[type] = NULL;
+	iput(inode);
+}
+
+int dquot_load_quota_sb(struct super_block *sb, int type, int format_id,
 	unsigned int flags)
 {
 	struct quota_format_type *fmt = find_quota_format(format_id);
-	struct super_block *sb = inode->i_sb;
 	struct quota_info *dqopt = sb_dqopt(sb);
 	int error;
 
 	if (!fmt)
 		return -ESRCH;
-	if (!S_ISREG(inode->i_mode)) {
-		error = -EACCES;
-		goto out_fmt;
-	}
-	if (IS_RDONLY(inode)) {
-		error = -EROFS;
-		goto out_fmt;
-	}
 	if (!sb->s_op->quota_write || !sb->s_op->quota_read ||
 	    (type == PRJQUOTA && sb->dq_op->get_projid == NULL)) {
 		error = -EINVAL;
@@ -2359,27 +2451,9 @@ static int vfs_load_quota_inode(struct inode *inode, int type, int format_id,
 		invalidate_bdev(sb->s_bdev);
 	}
 
-	if (!(dqopt->flags & DQUOT_QUOTA_SYS_FILE)) {
-		/* We don't want quota and atime on quota files (deadlocks
-		 * possible) Also nobody should write to the file - we use
-		 * special IO operations which ignore the immutable bit. */
-		inode_lock(inode);
-		inode->i_flags |= S_NOQUOTA;
-		inode_unlock(inode);
-		/*
-		 * When S_NOQUOTA is set, remove dquot references as no more
-		 * references can be added
-		 */
-		__dquot_drop(inode);
-	}
-
-	error = -EIO;
-	dqopt->files[type] = igrab(inode);
-	if (!dqopt->files[type])
-		goto out_file_flags;
 	error = -EINVAL;
 	if (!fmt->qf_ops->check_quota_file(sb, type))
-		goto out_file_init;
+		goto out_fmt;
 
 	dqopt->ops[type] = fmt->qf_ops;
 	dqopt->info[type].dqi_format = fmt;
@@ -2387,7 +2461,7 @@ static int vfs_load_quota_inode(struct inode *inode, int type, int format_id,
 	INIT_LIST_HEAD(&dqopt->info[type].dqi_dirty_list);
 	error = dqopt->ops[type]->read_file_info(sb, type);
 	if (error < 0)
-		goto out_file_init;
+		goto out_fmt;
 	if (dqopt->flags & DQUOT_QUOTA_SYS_FILE) {
 		spin_lock(&dq_data_lock);
 		dqopt->info[type].dqi_flags |= DQF_SYS_FILE;
@@ -2399,21 +2473,34 @@ static int vfs_load_quota_inode(struct inode *inode, int type, int format_id,
 
 	error = add_dquot_ref(sb, type);
 	if (error)
-		dquot_disable(sb, type, flags);
+		dquot_disable(sb, type,
+			      DQUOT_USAGE_ENABLED | DQUOT_LIMITS_ENABLED);
 
 	return error;
-out_file_init:
-	dqopt->files[type] = NULL;
-	iput(inode);
-out_file_flags:
-	inode_lock(inode);
-	inode->i_flags &= ~S_NOQUOTA;
-	inode_unlock(inode);
 out_fmt:
 	put_quota_format(fmt);
 
 	return error;
 }
+EXPORT_SYMBOL(dquot_load_quota_sb);
+
+/*
+ * Helper function to turn quotas on when we already have the inode of
+ * quota file and no quota information is loaded.
+ */
+static int vfs_load_quota_inode(struct inode *inode, int type, int format_id,
+	unsigned int flags)
+{
+	int err;
+
+	err = vfs_setup_quota_inode(inode, type);
+	if (err < 0)
+		return err;
+	err = dquot_load_quota_sb(inode->i_sb, type, format_id, flags);
+	if (err < 0)
+		vfs_cleanup_quota_inode(inode->i_sb, type);
+	return err;
+}
 
 /* Reenable quotas on remount RW */
 int dquot_resume(struct super_block *sb, int type)
@@ -2514,21 +2601,15 @@ int dquot_quota_on_mount(struct super_block *sb, char *qf_name,
 	struct dentry *dentry;
 	int error;
 
-	dentry = lookup_one_len_unlocked(qf_name, sb->s_root, strlen(qf_name));
+	dentry = lookup_positive_unlocked(qf_name, sb->s_root, strlen(qf_name));
 	if (IS_ERR(dentry))
 		return PTR_ERR(dentry);
 
-	if (d_really_is_negative(dentry)) {
-		error = -ENOENT;
-		goto out;
-	}
-
 	error = security_quota_on(dentry);
 	if (!error)
 		error = vfs_load_quota_inode(d_inode(dentry), type, format_id,
 				DQUOT_USAGE_ENABLED | DQUOT_LIMITS_ENABLED);
 
-out:
 	dput(dentry);
 	return error;
 }