btrfs: migrate eb_bitmap_offset() to folio interfaces

[BUG]
Test case btrfs/002 would fail if larger folios are enabled for
metadata:

 assertion failed: folio, in fs/btrfs/extent_io.c:4358
 ------------[ cut here ]------------
 kernel BUG at fs/btrfs/extent_io.c:4358!
 invalid opcode: 0000 [#1] PREEMPT SMP NOPTI
 CPU: 1 PID: 30916 Comm: fsstress Tainted: G           OE      6.7.0-rc3-custom+ #128
 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS unknown 2/2/2022
 RIP: 0010:assert_eb_folio_uptodate+0x98/0xe0 [btrfs]
 Call Trace:
  <TASK>
  extent_buffer_test_bit+0x3c/0x70 [btrfs]
  free_space_test_bit+0xcd/0x140 [btrfs]
  modify_free_space_bitmap+0x27a/0x430 [btrfs]
  add_to_free_space_tree+0x8d/0x160 [btrfs]
  __btrfs_free_extent.isra.0+0xef1/0x13c0 [btrfs]
  __btrfs_run_delayed_refs+0x786/0x13c0 [btrfs]
  btrfs_run_delayed_refs+0x33/0x120 [btrfs]
  btrfs_commit_transaction+0xa2/0x1350 [btrfs]
  iterate_supers+0x77/0xe0
  ksys_sync+0x60/0xa0
  __do_sys_sync+0xa/0x20
  do_syscall_64+0x3f/0xf0
  entry_SYSCALL_64_after_hwframe+0x6e/0x76
  </TASK>

[CAUSE]
The function extent_buffer_test_bit() is not folio compatible.

It still assumes the old fixed page size, when an extent buffer with
large folio passed in, only eb->folios[0] is populated.

Then if the target bit range falls in the 2nd page of the folio, then we
would check eb->folios[1], and trigger the ASSERT().

[FIX]
Just migrate eb_bitmap_offset() to folio interfaces, using the
folio_size() to replace PAGE_SIZE.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/extent_io.c

@@ -4459,22 +4459,22 @@ void copy_extent_buffer(const struct extent_buffer *dst,
 }
 
 /*
- * Calculate the page and offset of the byte containing the given bit number.
+ * Calculate the folio and offset of the byte containing the given bit number.
  *
  * @eb:           the extent buffer
  * @start:        offset of the bitmap item in the extent buffer
  * @nr:           bit number
- * @page_index:   return index of the page in the extent buffer that contains
+ * @folio_index:  return index of the folio in the extent buffer that contains
  *                the given bit number
- * @page_offset:  return offset into the page given by page_index
+ * @folio_offset: return offset into the folio given by folio_index
  *
  * This helper hides the ugliness of finding the byte in an extent buffer which
  * contains a given bit.
  */
 static inline void eb_bitmap_offset(const struct extent_buffer *eb,
 				    unsigned long start, unsigned long nr,
-				    unsigned long *page_index,
-				    size_t *page_offset)
+				    unsigned long *folio_index,
+				    size_t *folio_offset)
 {
 	size_t byte_offset = BIT_BYTE(nr);
 	size_t offset;
@@ -4484,10 +4484,10 @@ static inline void eb_bitmap_offset(const struct extent_buffer *eb,
 	 * the bitmap item in the extent buffer + the offset of the byte in the
 	 * bitmap item.
 	 */
-	offset = start + offset_in_page(eb->start) + byte_offset;
+	offset = start + offset_in_folio(eb->folios[0], eb->start) + byte_offset;
 
-	*page_index = offset >> PAGE_SHIFT;
-	*page_offset = offset_in_page(offset);
+	*folio_index = offset >> folio_shift(eb->folios[0]);
+	*folio_offset = offset_in_folio(eb->folios[0], offset);
 }
 
 /*
@@ -4500,15 +4500,13 @@ static inline void eb_bitmap_offset(const struct extent_buffer *eb,
 int extent_buffer_test_bit(const struct extent_buffer *eb, unsigned long start,
 			   unsigned long nr)
 {
-	u8 *kaddr;
-	struct page *page;
 	unsigned long i;
 	size_t offset;
+	u8 *kaddr;
 
 	eb_bitmap_offset(eb, start, nr, &i, &offset);
-	page = folio_page(eb->folios[i], 0);
 	assert_eb_folio_uptodate(eb, i);
-	kaddr = page_address(page);
+	kaddr = folio_address(eb->folios[i]);
 	return 1U & (kaddr[offset] >> (nr & (BITS_PER_BYTE - 1)));
 }