quota: Add support for ->get_nextdqblk() for VFS quota

Add infrastructure for supporting get_nextdqblk() callback for VFS
quotas. Translate the operation into a callback to appropriate
filesystem and consequently to quota format callback.
Signed-off-by: Jan Kara <jack@suse.cz>

fs/ext4/super.c

@@ -1132,6 +1132,7 @@ static const struct dquot_operations ext4_quota_operations = {
 	.alloc_dquot	= dquot_alloc,
 	.destroy_dquot	= dquot_destroy,
 	.get_projid	= ext4_get_projid,
+	.get_next_id	= dquot_get_next_id,
 };
 
 static const struct quotactl_ops ext4_qctl_operations = {

fs/quota/dquot.c

@@ -2031,6 +2031,21 @@ int dquot_commit_info(struct super_block *sb, int type)
 }
 EXPORT_SYMBOL(dquot_commit_info);
 
+int dquot_get_next_id(struct super_block *sb, struct kqid *qid)
+{
+	struct quota_info *dqopt = sb_dqopt(sb);
+	int err;
+
+	if (!dqopt->ops[qid->type]->get_next_id)
+		return -ENOSYS;
+	mutex_lock(&dqopt->dqio_mutex);
+	err = dqopt->ops[qid->type]->get_next_id(sb, qid);
+	mutex_unlock(&dqopt->dqio_mutex);
+
+	return err;
+}
+EXPORT_SYMBOL(dquot_get_next_id);
+
 /*
  * Definitions of diskquota operations.
  */
@@ -2042,6 +2057,7 @@ const struct dquot_operations dquot_operations = {
 	.write_info	= dquot_commit_info,
 	.alloc_dquot	= dquot_alloc,
 	.destroy_dquot	= dquot_destroy,
+	.get_next_id	= dquot_get_next_id,
 };
 EXPORT_SYMBOL(dquot_operations);
 
@@ -2565,6 +2581,27 @@ int dquot_get_dqblk(struct super_block *sb, struct kqid qid,
 }
 EXPORT_SYMBOL(dquot_get_dqblk);
 
+int dquot_get_next_dqblk(struct super_block *sb, struct kqid *qid,
+			 struct qc_dqblk *di)
+{
+	struct dquot *dquot;
+	int err;
+
+	if (!sb->dq_op->get_next_id)
+		return -ENOSYS;
+	err = sb->dq_op->get_next_id(sb, qid);
+	if (err < 0)
+		return err;
+	dquot = dqget(sb, *qid);
+	if (IS_ERR(dquot))
+		return PTR_ERR(dquot);
+	do_get_dqblk(dquot, di);
+	dqput(dquot);
+
+	return 0;
+}
+EXPORT_SYMBOL(dquot_get_next_dqblk);
+
 #define VFS_QC_MASK \
 	(QC_SPACE | QC_SPC_SOFT | QC_SPC_HARD | \
 	 QC_INO_COUNT | QC_INO_SOFT | QC_INO_HARD | \
@@ -2765,6 +2802,7 @@ const struct quotactl_ops dquot_quotactl_ops = {
 	.get_state	= dquot_get_state,
 	.set_info	= dquot_set_dqinfo,
 	.get_dqblk	= dquot_get_dqblk,
+	.get_nextdqblk	= dquot_get_next_dqblk,
 	.set_dqblk	= dquot_set_dqblk
 };
 EXPORT_SYMBOL(dquot_quotactl_ops);
@@ -2776,6 +2814,7 @@ const struct quotactl_ops dquot_quotactl_sysfile_ops = {
 	.get_state	= dquot_get_state,
 	.set_info	= dquot_set_dqinfo,
 	.get_dqblk	= dquot_get_dqblk,
+	.get_nextdqblk	= dquot_get_next_dqblk,
 	.set_dqblk	= dquot_set_dqblk
 };
 EXPORT_SYMBOL(dquot_quotactl_sysfile_ops);

fs/reiserfs/super.c

@@ -802,6 +802,7 @@ static const struct dquot_operations reiserfs_quota_operations = {
 	.write_info = reiserfs_write_info,
 	.alloc_dquot	= dquot_alloc,
 	.destroy_dquot	= dquot_destroy,
+	.get_next_id	= dquot_get_next_id,
 };
 
 static const struct quotactl_ops reiserfs_qctl_operations = {

include/linux/quota.h

@@ -306,6 +306,7 @@ struct quota_format_ops {
 	int (*read_dqblk)(struct dquot *dquot);		/* Read structure for one user */
 	int (*commit_dqblk)(struct dquot *dquot);	/* Write structure for one user */
 	int (*release_dqblk)(struct dquot *dquot);	/* Called when last reference to dquot is being dropped */
+	int (*get_next_id)(struct super_block *sb, struct kqid *qid);	/* Get next ID with existing structure in the quota file */
 };
 
 /* Operations working with dquots */
@@ -321,6 +322,8 @@ struct dquot_operations {
 	 * quota code only */
 	qsize_t *(*get_reserved_space) (struct inode *);
 	int (*get_projid) (struct inode *, kprojid_t *);/* Get project ID */
+	/* Get next ID with active quota structure */
+	int (*get_next_id) (struct super_block *sb, struct kqid *qid);
 };
 
 struct path;

include/linux/quotaops.h

@@ -82,6 +82,7 @@ int dquot_commit(struct dquot *dquot);
 int dquot_acquire(struct dquot *dquot);
 int dquot_release(struct dquot *dquot);
 int dquot_commit_info(struct super_block *sb, int type);
+int dquot_get_next_id(struct super_block *sb, struct kqid *qid);
 int dquot_mark_dquot_dirty(struct dquot *dquot);
 
 int dquot_file_open(struct inode *inode, struct file *file);
@@ -99,6 +100,8 @@ int dquot_get_state(struct super_block *sb, struct qc_state *state);
 int dquot_set_dqinfo(struct super_block *sb, int type, struct qc_info *ii);
 int dquot_get_dqblk(struct super_block *sb, struct kqid id,
 		struct qc_dqblk *di);
+int dquot_get_next_dqblk(struct super_block *sb, struct kqid *id,
+		struct qc_dqblk *di);
 int dquot_set_dqblk(struct super_block *sb, struct kqid id,
 		struct qc_dqblk *di);