btrfs: make btrfs_repair_io_failure() handle bs > ps cases without large folios

btrfs: make btrfs_repair_io_failure() handle bs > ps cases without large folios

Currently btrfs_repair_io_failure() only accept a single @paddr
parameter, and for bs > ps cases it's required that @paddr is backed by
a large folio.

That assumption has quite some limitations, preventing us from utilizing
true zero-copy direct-io and encoded read/writes.

To address the problem, enhance btrfs_repair_io_failure() by:

- Accept an array of paddrs, up to 64K / PAGE_SIZE entries
  This kind of acts like a bio_vec, but with very limited entries, as the
  function is only utilized to repair one fs data block, or a tree block.

  Both have an upper size limit (BTRFS_MAX_BLOCK_SIZE, i.e. 64K), so we
  don't need the full bio_vec thing to handle it.

- Allocate a bio with multiple slots
  Previously even for bs > ps cases, we only passed in a contiguous
  physical address range, thus a single slot will be enough.

  But not anymore, so we have to allocate a bio structure, other than
  using the on-stack one.

- Use on-stack memory to allocate @paddrs array
  It's at most 16 pages (4K page size, 64K block size), will take up at
  most 128 bytes.
  I think the on-stack cost is still acceptable.

- Add one extra check to make sure the repair bio is exactly one block

- Utilize btrfs_repair_io_failure() to submit a single bio for metadata
  This should improve the read-repair performance for metadata, as now
  we submit a node sized bio then wait, other than submit each block of
  the metadata and wait for each submitted block.

- Add one extra parameter indicating the step
  This is due to the fact that metadata step can be as large as
  nodesize, instead of sectorsize.
  So we need a way to distinguish metadata and data repair.

- Reduce the width of @length parameter of btrfs_repair_io_failure()
  Since we only call btrfs_repair_io_failure() on a single data or
  metadata block, u64 is overkilled.
  Use u32 instead and add one extra ASSERT()s to make sure the length
  never exceed BTRFS_MAX_BLOCK_SIZE.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>