btrfs: migrate various end io functions to folios

If we still go the old page based iterator functions, like
bio_for_each_segment_all(), we can hit middle pages of a folio (compound
page).

In that case if we set any page flag on those middle pages, we can
easily trigger VM_BUG_ON(), as for compound page flags, they should
follow their flag policies (normally only set on leading or tail pages).

To avoid such problem in the future full folio migration, here we do:

- Change from bio_for_each_segment_all() to bio_for_each_folio_all()
  This completely removes the ability to access the middle page.

- Add extra ASSERT()s for data read/write paths
  To ensure we only get single paged folio for data now.

- Rename those end io functions to follow a certain schema
  * end_bbio_compressed_read()
  * end_bbio_compressed_write()

    These two endio functions don't set any page flags, as they use pages
    not mapped to any address space.
    They can be very good candidates for higher order folio testing.

    And they are shared between compression and encoded IO.

  * end_bbio_data_read()
  * end_bbio_data_write()
  * end_bbio_meta_read()
  * end_bbio_meta_write()

  The old function names are not unified:
    - end_bio_extent_writepage()
    - end_bio_extent_readpage()
    - extent_buffer_write_end_io()
    - extent_buffer_read_end_io()

  They share no schema on where the "end_*io" string should be, nor can
  be confusing just using "extent_buffer" and "extent" to distinguish
  data and metadata paths.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/compression.c

@@ -264,7 +264,7 @@ void btrfs_free_compr_page(struct page *page)
 	put_page(page);
 }
 
-static void end_compressed_bio_read(struct btrfs_bio *bbio)
+static void end_bbio_comprssed_read(struct btrfs_bio *bbio)
 {
 	struct compressed_bio *cb = to_compressed_bio(bbio);
 	blk_status_t status = bbio->bio.bi_status;
@@ -337,7 +337,7 @@ static void btrfs_finish_compressed_write_work(struct work_struct *work)
  * This also calls the writeback end hooks for the file pages so that metadata
  * and checksums can be updated in the file.
  */
-static void end_compressed_bio_write(struct btrfs_bio *bbio)
+static void end_bbio_comprssed_write(struct btrfs_bio *bbio)
 {
 	struct compressed_bio *cb = to_compressed_bio(bbio);
 	struct btrfs_fs_info *fs_info = bbio->inode->root->fs_info;
@@ -384,7 +384,7 @@ void btrfs_submit_compressed_write(struct btrfs_ordered_extent *ordered,
 
 	cb = alloc_compressed_bio(inode, ordered->file_offset,
 				  REQ_OP_WRITE | write_flags,
-				  end_compressed_bio_write);
+				  end_bbio_comprssed_write);
 	cb->start = ordered->file_offset;
 	cb->len = ordered->num_bytes;
 	cb->compressed_pages = compressed_pages;
@@ -589,7 +589,7 @@ void btrfs_submit_compressed_read(struct btrfs_bio *bbio)
 	compressed_len = em->block_len;
 
 	cb = alloc_compressed_bio(inode, file_offset, REQ_OP_READ,
-				  end_compressed_bio_read);
+				  end_bbio_comprssed_read);
 
 	cb->start = em->orig_start;
 	em_len = em->len;