btrfs: zoned: use regular writes for relocation

Now that we have a dedicated block group for relocation, we can use
REQ_OP_WRITE instead of  REQ_OP_ZONE_APPEND for writing out the data on
relocation.
Reviewed-by: NNaohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: NJohannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

fs/btrfs/zoned.c

@@ -1490,6 +1490,17 @@ bool btrfs_use_zone_append(struct btrfs_inode *inode, u64 start)
 	if (!is_data_inode(&inode->vfs_inode))
 		return false;
 
+	/*
+	 * Using REQ_OP_ZONE_APPNED for relocation can break assumptions on the
+	 * extent layout the relocation code has.
+	 * Furthermore we have set aside own block-group from which only the
+	 * relocation "process" can allocate and make sure only one process at a
+	 * time can add pages to an extent that gets relocated, so it's safe to
+	 * use regular REQ_OP_WRITE for this special case.
+	 */
+	if (btrfs_is_data_reloc_root(inode->root))
+		return false;
+
 	cache = btrfs_lookup_block_group(fs_info, start);
 	ASSERT(cache);
 	if (!cache)