btrfs: zero the buffer before marking it dirty in btrfs_redirty_list_add

btrfs_redirty_list_add zeroes the buffer data and sets the
EXTENT_BUFFER_NO_CHECK to make sure writeback is fine with a bogus
header.  But it does that after already marking the buffer dirty, which
means that writeback could already be looking at the buffer.

Switch the order of operations around so that the buffer is only marked
dirty when we're ready to write it.

Fixes: d3575156 ("btrfs: zoned: redirty released extent buffers")
CC: stable@vger.kernel.org # 5.15+
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

fs/btrfs/zoned.c

@@ -1609,11 +1609,11 @@ void btrfs_redirty_list_add(struct btrfs_transaction *trans,
 	    !list_empty(&eb->release_list))
 		return;
 
+	memzero_extent_buffer(eb, 0, eb->len);
+	set_bit(EXTENT_BUFFER_NO_CHECK, &eb->bflags);
 	set_extent_buffer_dirty(eb);
 	set_extent_bits_nowait(&trans->dirty_pages, eb->start,
 			       eb->start + eb->len - 1, EXTENT_DIRTY);
-	memzero_extent_buffer(eb, 0, eb->len);
-	set_bit(EXTENT_BUFFER_NO_CHECK, &eb->bflags);
 
 	spin_lock(&trans->releasing_ebs_lock);
 	list_add_tail(&eb->release_list, &trans->releasing_ebs);