zonfs: Fix handling of read-only zones

The write pointer of zones in the read-only consition is defined as
invalid by the SCSI ZBC and ATA ZAC specifications. It is thus not
possible to determine the correct size of a read-only zone file on
mount. Fix this by handling read-only zones in the same manner as
offline zones by disabling all accesses to the zone (read and write)
and initializing the inode size of the read-only zone to 0).

For zones found to be in the read-only condition at runtime, only
disable write access to the zone and keep the size of the zone file to
its last updated value to allow the user to recover previously written
data.

Also fix zonefs documentation file to reflect this change.

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>

1 files changed, 21 insertions, 7 deletions

diff --git a/fs/zonefs/super.c b/fs/zonefs/super.c
index 69aee3dfb660..3ce9829a6936 100644
--- a/fs/zonefs/super.c
+++ b/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;