btrfs: remove on-stack paddrs[] array usage

btrfs: remove on-stack paddrs[] array usage

Since the bs > ps support, we have to handle cases where a data block is
inside several discontiguous pages.

Thus we need a local paddrs[] array to assemble a data block for bs > ps
cases.

However to handle all possible bs/ps combinations, we have to declare
such array using the max block size vs page size, no matter the current
block size and page size.

This adds 128 bytes on-stack memory usage for several call sites, and
also introduced several duplicated helpers to calculate checksum for a
data block:

- btrfs_calculate_block_csum_folio()
- btrfs_calculate_block_csum_pages()
- btrfs_check_block_csum()

The differences are mostly in how the data is passed.
The first one accepts a contiguous paddr range.
The second one accepts an array of paddrs[].
The last one is just a simple wrapper of the first one.

However the most common interface to iterate a data block is through
bio, and we have already converted most callers to use the bio based
interface, e.g. btrfs_bio_data_csum_ok() and btrfs_csum_one_bio_block().

Convert the remaining two call sites to address the remaining paddrs[]
usage:

- btrfs_calculate_block_csum_pages() inside verify_bio_data_sectors()
  This can be switched to btrfs_csum_one_bio_block().

  This removes the 128 bytes on-stack memory usage.

- btrfs_calculate_block_csum_pages() inside verify_one_sector()
  This call site doesn't use on-stack memory for paddrs[], but reuses
  the existing btrfs_raid_bio::bio_paddrs[] or
  btrfs_raid_bio::stripe_paddrs[].

  So implement a local version called calculate_block_csum_paddrs().

Now there is no fixed on-stack paddrs[] usage anymore.

Reviewed-by: Boris Burkov <boris@bur.io>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>