quota: Pass information that quota is stored in system file to userspace

Quota tools need to know whether quota is stored in a system file or in
classical aquota.{user|group} files. So pass this information as a flag
in GETINFO quotactl.
Signed-off-by: Jan Kara <jack@suse.cz>

fs/quota/dquot.c

@@ -2125,6 +2125,8 @@ static int vfs_load_quota_inode(struct inode *inode, int type, int format_id,
 		mutex_unlock(&dqopt->dqio_mutex);
 		goto out_file_init;
 	}
+	if (dqopt->flags & DQUOT_QUOTA_SYS_FILE)
+		dqopt->info[type].dqi_flags |= DQF_SYS_FILE;
 	mutex_unlock(&dqopt->dqio_mutex);
 	spin_lock(&dq_state_lock);
 	dqopt->flags |= dquot_state_flag(flags, type);
@@ -2464,7 +2466,7 @@ int dquot_get_dqinfo(struct super_block *sb, int type, struct if_dqinfo *ii)
 	spin_lock(&dq_data_lock);
 	ii->dqi_bgrace = mi->dqi_bgrace;
 	ii->dqi_igrace = mi->dqi_igrace;
-	ii->dqi_flags = mi->dqi_flags & DQF_MASK;
+	ii->dqi_flags = mi->dqi_flags & DQF_GETINFO_MASK;
 	ii->dqi_valid = IIF_ALL;
 	spin_unlock(&dq_data_lock);
 	mutex_unlock(&sb_dqopt(sb)->dqonoff_mutex);
@@ -2490,8 +2492,8 @@ int dquot_set_dqinfo(struct super_block *sb, int type, struct if_dqinfo *ii)
 	if (ii->dqi_valid & IIF_IGRACE)
 		mi->dqi_igrace = ii->dqi_igrace;
 	if (ii->dqi_valid & IIF_FLAGS)
-		mi->dqi_flags = (mi->dqi_flags & ~DQF_MASK) |
-				(ii->dqi_flags & DQF_MASK);
+		mi->dqi_flags = (mi->dqi_flags & ~DQF_SETINFO_MASK) |
+				(ii->dqi_flags & DQF_SETINFO_MASK);
 	spin_unlock(&dq_data_lock);
 	mark_info_dirty(sb, type);
 	/* Force write to disk */

include/linux/quota.h

@@ -230,7 +230,11 @@ struct mem_dqinfo {
 struct super_block;
 
 #define DQF_MASK 0xffff		/* Mask for format specific flags */
-#define DQF_INFO_DIRTY_B 16
+#define DQF_GETINFO_MASK 0x1ffff	/* Mask for flags passed to userspace */
+#define DQF_SETINFO_MASK 0xffff		/* Mask for flags modifiable from userspace */
+#define DQF_SYS_FILE_B		16
+#define DQF_SYS_FILE (1 << DQF_SYS_FILE_B)	/* Quota file stored as system file */
+#define DQF_INFO_DIRTY_B	31
 #define DQF_INFO_DIRTY (1 << DQF_INFO_DIRTY_B)	/* Is info dirty? */
 
 extern void mark_info_dirty(struct super_block *sb, int type);