because it will lead to debug assertion failure when buf_fix_count == 0.
This bug was introduced in r912.

added in r928.  Do not call btr_cur_get_block() in the debug assertion,
because the debug assertion there would fail.

We cannot call buf_block_get_space() or buf_block_get_page_no(),
because the assertions there can fail.

while trying to fix r909: invoke mem_erase_buf() before freeing the
buffer, but after interpreting block->buf_block.

ibuf_page(), ibuf_page_low(), ibuf_free_excess_pages(), ibuf_insert(),
buf_read_page(), buf_read_ahead_linear(), buf_read_recv_pages():
Add parameter zip_size.

btr_search_build_page_hash_index(), fsp_parse_init_file_page(),
ibuf_parse_bitmap_init(): Replace page_t* with buf_block_t*.

buf_read_ibuf_merge_pages(): Add const qualifiers.  Retrieve zip_size.

ibuf_merge_or_delete_for_page(): Replace page_t* with buf_block_t*.
Add parameter zip_size.

dict_index_get_nth_col_pos(), dict_index_get_sys_col_pos(),
dict_index_get_n_fields(), fil_page_get_type():
Add const qualifier to parameter.

dict_index_get_nth_field(): Implement as a macro unless #ifdef UNIV_DEBUG.

accessors returning pointers with macros that preserve const qualifiers.
In UNIV_DEBUG builds, retain the accessors and cast away constness there.

dfield_get_type(), dfield_get_data(), dtuple_get_nth_field(),
dict_table_get_nth_col(), dict_table_get_sys_col(): Implement as macro
unless #ifdef UNIV_DEBUG.

rec_get_nth_field(): Replace with rec_get_nth_field_offs() that does not
do pointer arithmetics.  Implement rec_get_nth_field() as a macro.

passed as TRUE.

Enclose hash_table_t::adaptive and buf_block_t::n_pointers in
#ifdef UNIV_DEBUG.

btr_search_drop_page_hash_index(): Enclose the corruption check
(which depends on buf_block_t::n_pointers) in #ifdef UNIV_DEBUG.

calling buf_block_align() in btr_pcur_move_backward_from_page().
Also, enclose some assertions about page_is_comp() in #ifdef UNIV_BTR_DEBUG.

Replace page_t* or page_zip_des_t* parameters in some functions with
buf_block_t*.

buf_frame_get_page_zip(): Disable unless #ifdef UNIV_DEBUG || UNIV_ZIP_DEBUG.

btr_cur_t: Add buf_block_t* page_block.

btr_pcur_get_block(), btr_cur_get_block(), btr_cur_get_page_zip():
New functions.

btr_cur_position(): Add the parameter block.

and modify some functions to return const pointers.  Add const qualifiers
to local variable declarations or casts to remove the const qualifier
in those places where write access is needed.

the symbol UNIV_DEBUG_PRINT, which was introduced in r729.

buf_LRU_print(), buf_print(): Replace #ifdef UNIV_DEBUG_PRINT
with #if defined UNIV_DEBUG || defined UNIV_DEBUG_PRINT.

of rec accessor functions.

Trim the fetched prefix with dtype_get_at_most_n_mbchars().

and remove the buf_block_align() call.

Replace buf_frame_modify_clock_inc() with buf_block_modify_clock_inc().
Replace buf_frame_get_lock_hash_val() with buf_block_get_lock_hash_val().
Replace buf_frame_get_lock_mutex() with buf_block_get_lock_mutex().

page_create_zip(), page_create(), page_create_low(), btr_page_free(),
btr_page_free_low(): Replace page_t with buf_block_t.

invoke mem_erase_buf() only after interpreting block->buf_block.

ibuf_update_free_bits_low(), ibuf_update_free_bits_for_two_pages_low(),
ibuf_set_free_bits_low(): Replace page_t with buf_block_t.

ibuf_reset_free_bits(): Remove, as there already is a similar function
ibuf_reset_free_bits_with_type().

ibuf_reset_free_bits_with_type(), ibuf_set_free_bits(),
ibuf_update_free_bits_if_full(), btr_leaf_page_release(),
buf_page_make_young(): Replace page_t with buf_block_t.

btr_compress(): Replace btr_page_get() with btr_block_get().

mlog_write_initial_log_record_fast(): Remove the buf_block_align() call
unless #ifdef UNIV_DEBUG.

btr_cur_update_in_place(): Replace buf_frame_get_page_zip() with
buf_block_get_page_zip().

btr_page_create(), btr_page_empty(): Replace the parameter page with block.

btr_attach_half_pages(): Use btr_block_get() instead of btr_page_get().
Remove buf_block_align() calls.

btr_cur_latch_leaves(): Remove duplicated code.  Use btr_block_get()
instead of btr_page_get().  Remove buf_block_align() calls.

When allocating a block from heap->free_block, set buf_block.

with buf_block_alloc() and buf_block_free(), in order to
avoid buf_block_align() calls.

btr_block_get(): New function to return buf_block_t.

btr_page_alloc(), buf_page_get_release_on_io(), buf_page_get_gen(),
buf_page_create(), fseg_create(), fseg_create_general(): Return buf_block_t.

buf_page_get_known_nowait(): Expect buf_block_t instead of buf_frame_t.

buf_frame_get_newest_modification(): Replace with
buf_block_get_newest_modification().

buf_page_dbg_add_level(): Replace with buf_block_dbg_add_level().

buf_block_get_zip_size(): New function.

buf_block_get_page_zip(): Reintroduce.

recv_recover_page(): Replace page, space, page_no with block.

ibuf_bitmap_page_init(): Replace page, zip_size with block.

ibuf_parse_bitmap_init(): Remove the parameter zip_size.

btr_search_drop_page_hash_index(): Replace page with block.

with page_get_page_no() and page_get_space_id().  We want to avoid
buf_block_align() calls, and the page_no and space_id are now stamped
on the pages early on.

dict_table_add_system_columns() to dict_table_add_to_cache().

buf_flush_init_for_writing(): Remove parameters space, page_no.

fsp_init_file_page_low(): Wriet space_id and page_no to the page.

fil_create_new_single_table_tablespace(): Write space_id to the page.

This error was introduced in r867.

Replace ut_ad(mtr_memo_contains(mtr, buf_block_align(ptr), ...))
with ut_ad(mtr_memo_contains_page(mtr, ptr, ...)) in order to reduce the
number of buf_block_align() calls.

ut_align_down(), or ut_align_offset().

dict_load_foreigns(): Enclose in #ifndef UNIV_HOTBACKUP.

fil_extend_tablespaces_to_stored_len(): Pass zip_size to fil_read().

buf_page_init_for_backup_restore(): Add parameter zip_size.
Enclose the declaration in buf0buf.h in #ifdef UNIV_HOTBACKUP.

recv_apply_log_recs_for_backup(): Replace the local variable "page"
with the local variable "block".  Add local variable zip_size.

TODO: test this with InnoDB Hot Backup 3.0

of tests are failing with trunk -r869, with this revision using uncompressed
storage, and with this revision hard-wired to use 1-kilobyte compressed pages
and innodb_file_per_table.

btr_push_update_extern_fields(): Do not call ut_ulint_sort() if n_pushed == 0.

btr_copy_externally_stored_field_prefix_low(): Replace ut_max() with ut_min().

os_aio_simulated_handle() before and after initiating a write.  We
cannot easily pass the compressed page sizes to this function.  The
check could only be performed on uncompressed pages.