Merge tag 'zonefs-5.6-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/dlemoal/zonefs

Pull zonefs fix from Damien Le Moal:
 "A single fix from me to correctly handle the size of read-only zone
  files"

* tag 'zonefs-5.6-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/dlemoal/zonefs:
  zonfs: Fix handling of read-only zones

Documentation/filesystems/zonefs.txt

@@ -258,11 +258,11 @@ conditions.
     |    option    | condition | size     read    write    read    write |
     +--------------+-----------+-----------------------------------------+
     |              | good      | fixed    yes     no       yes     yes   |
-    | remount-ro   | read-only | fixed    yes     no       yes     no    |
+    | remount-ro   | read-only | as is    yes     no       yes     no    |
     | (default)    | offline   |   0      no      no       no      no    |
     +--------------+-----------+-----------------------------------------+
     |              | good      | fixed    yes     no       yes     yes   |
-    | zone-ro      | read-only | fixed    yes     no       yes     no    |
+    | zone-ro      | read-only | as is    yes     no       yes     no    |
     |              | offline   |   0      no      no       no      no    |
     +--------------+-----------+-----------------------------------------+
     |              | good      |   0      no      no       yes     yes   |
@@ -270,7 +270,7 @@ conditions.
     |              | offline   |   0      no      no       no      no    |
     +--------------+-----------+-----------------------------------------+
     |              | good      | fixed    yes     yes      yes     yes   |
-    | repair       | read-only | fixed    yes     no       yes     no    |
+    | repair       | read-only | as is    yes     no       yes     no    |
     |              | offline   |   0      no      no       no      no    |
     +--------------+-----------+-----------------------------------------+
 
@@ -307,8 +307,16 @@ condition changes. The defined behaviors are as follow:
 * zone-offline
 * repair
 
-The I/O error actions defined for each behavior are detailed in the previous
-section.
+The run-time I/O error actions defined for each behavior are detailed in the
+previous section. Mount time I/O errors will cause the mount operation to fail.
+The handling of read-only zones also differs between mount-time and run-time.
+If a read-only zone is found at mount time, the zone is always treated in the
+same manner as offline zones, that is, all accesses are disabled and the zone
+file size set to 0. This is necessary as the write pointer of read-only zones
+is defined as invalib by the ZBC and ZAC standards, making it impossible to
+discover the amount of data that has been written to the zone. In the case of a
+read-only zone discovered at run-time, as indicated in the previous section.
+the size of the zone file is left unchanged from its last updated value.
 
 Zonefs User Space Tools
 =======================

fs/zonefs/super.c

@@ -178,7 +178,8 @@ static void zonefs_update_stats(struct inode *inode, loff_t new_isize)
  * amount of readable data in the zone.
  */
 static loff_t zonefs_check_zone_condition(struct inode *inode,
-					  struct blk_zone *zone, bool warn)
+					  struct blk_zone *zone, bool warn,
+					  bool mount)
 {
 	struct zonefs_inode_info *zi = ZONEFS_I(inode);
 
@@ -196,13 +197,26 @@ static loff_t zonefs_check_zone_condition(struct inode *inode,
 		zone->wp = zone->start;
 		return 0;
 	case BLK_ZONE_COND_READONLY:
-		/* Do not allow writes in read-only zones */
+		/*
+		 * The write pointer of read-only zones is invalid. If such a
+		 * zone is found during mount, the file size cannot be retrieved
+		 * so we treat the zone as offline (mount == true case).
+		 * Otherwise, keep the file size as it was when last updated
+		 * so that the user can recover data. In both cases, writes are
+		 * always disabled for the zone.
+		 */
 		if (warn)
 			zonefs_warn(inode->i_sb, "inode %lu: read-only zone\n",
 				    inode->i_ino);
 		inode->i_flags |= S_IMMUTABLE;
+		if (mount) {
+			zone->cond = BLK_ZONE_COND_OFFLINE;
+			inode->i_mode &= ~0777;
+			zone->wp = zone->start;
+			return 0;
+		}
 		inode->i_mode &= ~0222;
-		/* fallthrough */
+		return i_size_read(inode);
 	default:
 		if (zi->i_ztype == ZONEFS_ZTYPE_CNV)
 			return zi->i_max_size;
@@ -231,7 +245,7 @@ static int zonefs_io_error_cb(struct blk_zone *zone, unsigned int idx,
 	 * as there is no inconsistency between the inode size and the amount of
 	 * data writen in the zone (data_size).
 	 */
-	data_size = zonefs_check_zone_condition(inode, zone, true);
+	data_size = zonefs_check_zone_condition(inode, zone, true, false);
 	isize = i_size_read(inode);
 	if (zone->cond != BLK_ZONE_COND_OFFLINE &&
 	    zone->cond != BLK_ZONE_COND_READONLY &&
@@ -274,7 +288,7 @@ static int zonefs_io_error_cb(struct blk_zone *zone, unsigned int idx,
 		if (zone->cond != BLK_ZONE_COND_OFFLINE) {
 			zone->cond = BLK_ZONE_COND_OFFLINE;
 			data_size = zonefs_check_zone_condition(inode, zone,
-								false);
+								false, false);
 		}
 	} else if (zone->cond == BLK_ZONE_COND_READONLY ||
 		   sbi->s_mount_opts & ZONEFS_MNTOPT_ERRORS_ZRO) {
@@ -283,7 +297,7 @@ static int zonefs_io_error_cb(struct blk_zone *zone, unsigned int idx,
 		if (zone->cond != BLK_ZONE_COND_READONLY) {
 			zone->cond = BLK_ZONE_COND_READONLY;
 			data_size = zonefs_check_zone_condition(inode, zone,
-								false);
+								false, false);
 		}
 	}
 
@@ -975,7 +989,7 @@ static void zonefs_init_file_inode(struct inode *inode, struct blk_zone *zone,
 	zi->i_zsector = zone->start;
 	zi->i_max_size = min_t(loff_t, MAX_LFS_FILESIZE,
 			       zone->len << SECTOR_SHIFT);
-	zi->i_wpoffset = zonefs_check_zone_condition(inode, zone, true);
+	zi->i_wpoffset = zonefs_check_zone_condition(inode, zone, true, true);
 
 	inode->i_uid = sbi->s_uid;
 	inode->i_gid = sbi->s_gid;