btrfs-progs: zoned: check SB zone existence properly

Currently, write_dev_supers() compares the superblock location vs the size
of the device to check if it can write the superblock. This is not correct
for a zoned device, whose superblock location is different than a regular
device.

Introduce check_sb_location() to check if the superblock zone exists for
the zoned case.

Running btrfs check can fail on a certain zoned device setup (e.g,
zone size = 128MB, device size = 16GB).

From generic/330:

  yes | btrfs check --repair --force /dev/nullb1
  [1/7] checking root items
  Fixed 0 roots.
  [2/7] checking extents
  ERROR: zoned: failed to read zone info of 4096 and 4097: Invalid argument
  ERROR: failed to write super block for devid 1: write error: Input/output error
  failed to write new super block err -5
  failed to repair damaged filesystem, aborting

This happens because write_dev_supers() is comparing the original
superblock location vs the device size to check if it can write out a
superblock copy or not.

For the above example, since the first copy location (64MB) < device size
(16GB), it tries to write out the copy. But, the copy must be written into
zone 4096 (512G / zone size (128M) = 4096), which is out of the device.

Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>

kernel-shared/disk-io.c

@@ -1998,6 +1998,13 @@ int btrfs_read_dev_super(int fd, struct btrfs_super_block *sb, u64 sb_bytenr,
 	return transid > 0 ? 0 : -1;
 }
 
+static bool check_sb_location(struct btrfs_device *device, u64 bytenr)
+{
+	if (!device->zone_info)
+		return bytenr + BTRFS_SUPER_INFO_SIZE <= device->total_bytes;
+	return btrfs_sb_zone_exists(device, bytenr);
+}
+
 static int write_dev_supers(struct btrfs_fs_info *fs_info,
 			    struct btrfs_super_block *sb,
 			    struct btrfs_device *device)
@@ -2048,7 +2055,7 @@ static int write_dev_supers(struct btrfs_fs_info *fs_info,
 
 	for (i = 0; i < BTRFS_SUPER_MIRROR_MAX; i++) {
 		bytenr = btrfs_sb_offset(i);
-		if (bytenr + BTRFS_SUPER_INFO_SIZE > device->total_bytes)
+		if (!check_sb_location(device, bytenr))
 			break;
 
 		btrfs_set_super_bytenr(sb, bytenr);

kernel-shared/zoned.c

@@ -999,6 +999,14 @@ int btrfs_wipe_temporary_sb(struct btrfs_fs_devices *fs_devices)
 	return ret;
 }
 
+bool btrfs_sb_zone_exists(struct btrfs_device *device, u64 bytenr)
+{
+	u32 zone_num = sb_bytenr_to_sb_zone(bytenr,
+					    ilog2(device->zone_info->zone_size));
+
+	return zone_num + 1 <= device->zone_info->nr_zones - 1;
+}
+
 #endif
 
 int btrfs_get_dev_zone_info_all_devices(struct btrfs_fs_info *fs_info)

kernel-shared/zoned.h

@@ -153,6 +153,7 @@ int btrfs_reset_all_zones(int fd, struct btrfs_zoned_device_info *zinfo);
 int zero_zone_blocks(int fd, struct btrfs_zoned_device_info *zinfo, off_t start,
 		     size_t len);
 int btrfs_wipe_temporary_sb(struct btrfs_fs_devices *fs_devices);
+bool btrfs_sb_zone_exists(struct btrfs_device *device, u64 bytenr);
 
 #else
 
@@ -225,6 +226,11 @@ static inline bool zoned_profile_supported(u64 map_type, bool rst)
 	return false;
 }
 
+static inline bool btrfs_sb_zone_exists(struct btrfs_device *device, u64 bytenr)
+{
+	return true;
+}
+
 #endif /* BTRFS_ZONED */
 
 /*