[PATCH 05/12] quota: Use optional inode field for i_dquot pointers

[Jan Kara <jack@suse.cz>]

i_dquot is a first candidate for using optional inode fields since it is
used by relatively few filesystems (ext?, ocfs2, jfs, reiserfs). We
cannot just pass quota pointers from filesystems to quota functions
because during quotaon and quotaoff we have to traverse list of all
inodes and manipulate i_dquot pointers for each inode.

Firstly, we setup optional inode field so that it points at i_dquot
array in struct inode and convert quota code to use the accessor
function.

Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/quota/dquot.c   | 51 ++++++++++++++++++++++++++++-----------------------
 fs/super.c         |  3 +++
 include/linux/fs.h |  1 +
 3 files changed, 32 insertions(+), 23 deletions(-)

diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index f2d0eee9d1f1..ecb8732fe299 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -893,6 +893,11 @@ out:
 }
 EXPORT_SYMBOL(dqget);
 
+static inline struct dquot **i_dquot(const struct inode *inode)
+{
+	return ((struct dquot **)inode_field(inode, IF_DQUOTS));
+}
+
 static int dqinit_needed(struct inode *inode, int type)
 {
 	int cnt;
@@ -900,9 +905,9 @@ static int dqinit_needed(struct inode *inode, int type)
 	if (IS_NOQUOTA(inode))
 		return 0;
 	if (type != -1)
-		return !inode->i_dquot[type];
+		return !i_dquot(inode)[type];
 	for (cnt = 0; cnt < MAXQUOTAS; cnt++)
-		if (!inode->i_dquot[cnt])
+		if (!i_dquot(inode)[cnt])
 			return 1;
 	return 0;
 }
@@ -965,9 +970,9 @@ static void add_dquot_ref(struct super_block *sb, int type)
 static void remove_inode_dquot_ref(struct inode *inode, int type,
 				   struct list_head *tofree_head)
 {
-	struct dquot *dquot = inode->i_dquot[type];
+	struct dquot *dquot = i_dquot(inode)[type];
 
-	inode->i_dquot[type] = NULL;
+	i_dquot(inode)[type] = NULL;
 	if (!dquot)
 		return;
 
@@ -1402,7 +1407,7 @@ static void __dquot_initialize(struct inode *inode, int type)
 		 * we check it without locking here to avoid unnecessary
 		 * dqget()/dqput() calls.
 		 */
-		if (inode->i_dquot[cnt])
+		if (i_dquot(inode)[cnt])
 			continue;
 		init_needed = 1;
 
@@ -1433,8 +1438,8 @@ static void __dquot_initialize(struct inode *inode, int type)
 		/* We could race with quotaon or dqget() could have failed */
 		if (!got[cnt])
 			continue;
-		if (!inode->i_dquot[cnt]) {
-			inode->i_dquot[cnt] = got[cnt];
+		if (!i_dquot(inode)[cnt]) {
+			i_dquot(inode)[cnt] = got[cnt];
 			got[cnt] = NULL;
 			/*
 			 * Make quota reservation system happy if someone
@@ -1442,7 +1447,7 @@ static void __dquot_initialize(struct inode *inode, int type)
 			 */
 			rsv = inode_get_rsv_space(inode);
 			if (unlikely(rsv))
-				dquot_resv_space(inode->i_dquot[cnt], rsv);
+				dquot_resv_space(i_dquot(inode)[cnt], rsv);
 		}
 	}
 out_err:
@@ -1472,8 +1477,8 @@ static void __dquot_drop(struct inode *inode)
 
 	spin_lock(&dq_data_lock);
 	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
-		put[cnt] = inode->i_dquot[cnt];
-		inode->i_dquot[cnt] = NULL;
+		put[cnt] = i_dquot(inode)[cnt];
+		i_dquot(inode)[cnt] = NULL;
 	}
 	spin_unlock(&dq_data_lock);
 	dqput_all(put);
@@ -1494,7 +1499,7 @@ void dquot_drop(struct inode *inode)
 	 * add quota pointers back anyway.
 	 */
 	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
-		if (inode->i_dquot[cnt])
+		if (i_dquot(inode)[cnt])
 			break;
 	}
 
@@ -1595,7 +1600,7 @@ int __dquot_alloc_space(struct inode *inode, qsize_t number, int flags)
 {
 	int cnt, ret = 0, index;
 	struct dquot_warn warn[MAXQUOTAS];
-	struct dquot **dquots = inode->i_dquot;
+	struct dquot **dquots = i_dquot(inode);
 	int reserve = flags & DQUOT_SPACE_RESERVE;
 
 	if (!dquot_active(inode)) {
@@ -1647,7 +1652,7 @@ int dquot_alloc_inode(const struct inode *inode)
 {
 	int cnt, ret = 0, index;
 	struct dquot_warn warn[MAXQUOTAS];
-	struct dquot * const *dquots = inode->i_dquot;
+	struct dquot * const *dquots = i_dquot(inode);
 
 	if (!dquot_active(inode))
 		return 0;
@@ -1696,14 +1701,14 @@ int dquot_claim_space_nodirty(struct inode *inode, qsize_t number)
 	spin_lock(&dq_data_lock);
 	/* Claim reserved quotas to allocated quotas */
 	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
-		if (inode->i_dquot[cnt])
-			dquot_claim_reserved_space(inode->i_dquot[cnt],
+		if (i_dquot(inode)[cnt])
+			dquot_claim_reserved_space(i_dquot(inode)[cnt],
 							number);
 	}
 	/* Update inode bytes */
 	inode_claim_rsv_space(inode, number);
 	spin_unlock(&dq_data_lock);
-	mark_all_dquot_dirty(inode->i_dquot);
+	mark_all_dquot_dirty(i_dquot(inode));
 	srcu_read_unlock(&dquot_srcu, index);
 	return 0;
 }
@@ -1725,14 +1730,14 @@ void dquot_reclaim_space_nodirty(struct inode *inode, qsize_t number)
 	spin_lock(&dq_data_lock);
 	/* Claim reserved quotas to allocated quotas */
 	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
-		if (inode->i_dquot[cnt])
-			dquot_reclaim_reserved_space(inode->i_dquot[cnt],
+		if (i_dquot(inode)[cnt])
+			dquot_reclaim_reserved_space(i_dquot(inode)[cnt],
 						     number);
 	}
 	/* Update inode bytes */
 	inode_reclaim_rsv_space(inode, number);
 	spin_unlock(&dq_data_lock);
-	mark_all_dquot_dirty(inode->i_dquot);
+	mark_all_dquot_dirty(i_dquot(inode));
 	srcu_read_unlock(&dquot_srcu, index);
 	return;
 }
@@ -1745,7 +1750,7 @@ void __dquot_free_space(struct inode *inode, qsize_t number, int flags)
 {
 	unsigned int cnt;
 	struct dquot_warn warn[MAXQUOTAS];
-	struct dquot **dquots = inode->i_dquot;
+	struct dquot **dquots = i_dquot(inode);
 	int reserve = flags & DQUOT_SPACE_RESERVE, index;
 
 	if (!dquot_active(inode)) {
@@ -1788,7 +1793,7 @@ void dquot_free_inode(const struct inode *inode)
 {
 	unsigned int cnt;
 	struct dquot_warn warn[MAXQUOTAS];
-	struct dquot * const *dquots = inode->i_dquot;
+	struct dquot * const *dquots = i_dquot(inode);
 	int index;
 
 	if (!dquot_active(inode))
@@ -1865,7 +1870,7 @@ 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] = inode->i_dquot[cnt];
+		transfer_from[cnt] = i_dquot(inode)[cnt];
 		ret = check_idq(transfer_to[cnt], 1, &warn_to[cnt]);
 		if (ret)
 			goto over_quota;
@@ -1901,7 +1906,7 @@ int __dquot_transfer(struct inode *inode, struct dquot **transfer_to)
 		dquot_incr_space(transfer_to[cnt], cur_space);
 		dquot_resv_space(transfer_to[cnt], rsv_space);
 
-		inode->i_dquot[cnt] = transfer_to[cnt];
+		i_dquot(inode)[cnt] = transfer_to[cnt];
 	}
 	spin_unlock(&dq_data_lock);
 
diff --git a/fs/super.c b/fs/super.c
index c6c9b2de9e31..9ae340f857ee 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -228,6 +228,9 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags)
 	s->s_op = &default_op;
 	s->s_time_gran = 1000000000;
 	s->cleancache_poolid = -1;
+#ifdef CONFIG_QUOTA
+	s->s_inode_fields[IF_DQUOTS] = offsetof(struct inode, i_dquot);
+#endif
 
 	s->s_shrink.seeks = DEFAULT_SEEKS;
 	s->s_shrink.scan_objects = super_cache_scan;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index f2468786a36b..4b7b62543786 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -617,6 +617,7 @@ struct inode {
 
 /* Optional inode fields (stored in filesystems inode if the fs needs them) */
 enum inode_fields {
+	IF_DQUOTS,	/* Quota pointers: struct dquot *foo[MAXQUOTAS] */
 	IF_FIELD_NR	/* Number of optional inode fields */
 };
 
-- 
1.8.1.4