btrfs: subpage: add bitmap for PageChecked flag

Although in btrfs we have very limited usage of PageChecked flag, it's
still some page flag not yet subpage compatible.

Fix it by introducing btrfs_subpage::checked_offset to do the convert.

For most call sites, especially for free-space cache, COW fixup and
btrfs_invalidatepage(), they all work in full page mode anyway.

For other call sites, they work as subpage compatible mode.

Some call sites need extra modification:

- btrfs_drop_pages()
  Needs extra parameter to get the real range we need to clear checked
  flag.

  Also since btrfs_drop_pages() will accept pages beyond the dirtied
  range, update btrfs_subpage_clamp_range() to handle such case
  by setting @len to 0 if the page is beyond target range.

- btrfs_invalidatepage()
  We need to call subpage helper before calling __btrfs_releasepage(),
  or it will trigger ASSERT() as page->private will be cleared.

- btrfs_verify_data_csum()
  In theory we don't need the io_bio->csum check anymore, but it's
  won't hurt.  Just change the comment.

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

1 files changed, 5 insertions, 1 deletions

diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 0d26819b1cf6..f3fee88c8ee0 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -22,6 +22,7 @@
 #include "delalloc-space.h"
 #include "block-group.h"
 #include "discard.h"
+#include "subpage.h"
 
 #define BITS_PER_BITMAP		(PAGE_SIZE * 8UL)
 #define MAX_CACHE_BYTES_PER_GIG	SZ_64K
@@ -411,7 +412,10 @@ static void io_ctl_drop_pages(struct btrfs_io_ctl *io_ctl)
 
 	for (i = 0; i < io_ctl->num_pages; i++) {
 		if (io_ctl->pages[i]) {
-			ClearPageChecked(io_ctl->pages[i]);
+			btrfs_page_clear_checked(io_ctl->fs_info,
+					io_ctl->pages[i],
+					page_offset(io_ctl->pages[i]),
+					PAGE_SIZE);
 			unlock_page(io_ctl->pages[i]);
 			put_page(io_ctl->pages[i]);
 		}