btrfs: cleanup metadata page pointer usage

Although we have migrated extent_buffer::pages[] to folios[], we're
still mostly using the folio_page() help to grab the page.

This patch would do the following cleanups for metadata:

- Introduce num_extent_folios() helper
  This is to replace most num_extent_pages() callers.

- Use num_extent_folios() to iterate future large folios
  This allows us to use things like
  bio_add_folio()/bio_add_folio_nofail(), and only set the needed flags
  for the folio (aka the leading/tailing page), which reduces the loop
  iteration to 1 for large folios.

- Change metadata related functions to use folio pointers
  Including their function name, involving:
  * attach_extent_buffer_page()
  * detach_extent_buffer_page()
  * page_range_has_eb()
  * btrfs_release_extent_buffer_pages()
  * btree_clear_page_dirty()
  * btrfs_page_inc_eb_refs()
  * btrfs_page_dec_eb_refs()

- Change btrfs_is_subpage() to accept an address_space pointer
  This is to allow both page->mapping and folio->mapping to be utilized.
  As data is still using the old per-page code, and may keep so for a
  while.

- Special corner case place holder for future order mismatches between
  extent buffer and inode filemap
  For now it's  just a block of comments and a dead ASSERT(), no real
  handling yet.

The subpage code would still go page, just because subpage and large
folio are conflicting conditions, thus we don't need to bother subpage
with higher order folios at all. Just folio_page(folio, 0) would be
enough.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ minor styling tweaks ]
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 28 insertions, 27 deletions

diff --git a/fs/btrfs/subpage.c b/fs/btrfs/subpage.c
index caf0013f2545..f11ebaf87def 100644
--- a/fs/btrfs/subpage.c
+++ b/fs/btrfs/subpage.c
@@ -64,7 +64,7 @@
  *   This means a slightly higher tree locking latency.
  */
 
-bool btrfs_is_subpage(const struct btrfs_fs_info *fs_info, struct page *page)
+bool btrfs_is_subpage(const struct btrfs_fs_info *fs_info, struct address_space *mapping)
 {
 	if (fs_info->sectorsize >= PAGE_SIZE)
 		return false;
@@ -74,8 +74,7 @@ bool btrfs_is_subpage(const struct btrfs_fs_info *fs_info, struct page *page)
 	 * mapping. And if page->mapping->host is data inode, it's subpage.
 	 * As we have ruled our sectorsize >= PAGE_SIZE case already.
 	 */
-	if (!page->mapping || !page->mapping->host ||
-	    is_data_inode(page->mapping->host))
+	if (!mapping || !mapping->host || is_data_inode(mapping->host))
 		return true;
 
 	/*
@@ -129,7 +128,7 @@ int btrfs_attach_subpage(const struct btrfs_fs_info *fs_info,
 		ASSERT(PageLocked(page));
 
 	/* Either not subpage, or the folio already has private attached. */
-	if (!btrfs_is_subpage(fs_info, page) || folio_test_private(folio))
+	if (!btrfs_is_subpage(fs_info, page->mapping) || folio_test_private(folio))
 		return 0;
 
 	subpage = btrfs_alloc_subpage(fs_info, type);
@@ -147,7 +146,7 @@ void btrfs_detach_subpage(const struct btrfs_fs_info *fs_info,
 	struct btrfs_subpage *subpage;
 
 	/* Either not subpage, or the folio already has private attached. */
-	if (!btrfs_is_subpage(fs_info, page) || !folio_test_private(folio))
+	if (!btrfs_is_subpage(fs_info, page->mapping) || !folio_test_private(folio))
 		return;
 
 	subpage = folio_detach_private(folio);
@@ -193,33 +192,29 @@ void btrfs_free_subpage(struct btrfs_subpage *subpage)
  * detach_extent_buffer_page() won't detach the folio private while we're still
  * allocating the extent buffer.
  */
-void btrfs_page_inc_eb_refs(const struct btrfs_fs_info *fs_info,
-			    struct page *page)
+void btrfs_folio_inc_eb_refs(const struct btrfs_fs_info *fs_info, struct folio *folio)
 {
-	struct folio *folio = page_folio(page);
 	struct btrfs_subpage *subpage;
 
-	if (!btrfs_is_subpage(fs_info, page))
+	if (!btrfs_is_subpage(fs_info, folio->mapping))
 		return;
 
-	ASSERT(folio_test_private(folio) && page->mapping);
-	lockdep_assert_held(&page->mapping->private_lock);
+	ASSERT(folio_test_private(folio) && folio->mapping);
+	lockdep_assert_held(&folio->mapping->private_lock);
 
 	subpage = folio_get_private(folio);
 	atomic_inc(&subpage->eb_refs);
 }
 
-void btrfs_page_dec_eb_refs(const struct btrfs_fs_info *fs_info,
-			    struct page *page)
+void btrfs_folio_dec_eb_refs(const struct btrfs_fs_info *fs_info, struct folio *folio)
 {
-	struct folio *folio = page_folio(page);
 	struct btrfs_subpage *subpage;
 
-	if (!btrfs_is_subpage(fs_info, page))
+	if (!btrfs_is_subpage(fs_info, folio->mapping))
 		return;
 
-	ASSERT(folio_test_private(folio) && page->mapping);
-	lockdep_assert_held(&page->mapping->private_lock);
+	ASSERT(folio_test_private(folio) && folio->mapping);
+	lockdep_assert_held(&folio->mapping->private_lock);
 
 	subpage = folio_get_private(folio);
 	ASSERT(atomic_read(&subpage->eb_refs));
@@ -352,7 +347,7 @@ int btrfs_page_start_writer_lock(const struct btrfs_fs_info *fs_info,
 {
 	struct folio *folio = page_folio(page);
 
-	if (unlikely(!fs_info) || !btrfs_is_subpage(fs_info, page)) {
+	if (unlikely(!fs_info) || !btrfs_is_subpage(fs_info, page->mapping)) {
 		lock_page(page);
 		return 0;
 	}
@@ -369,7 +364,7 @@ int btrfs_page_start_writer_lock(const struct btrfs_fs_info *fs_info,
 void btrfs_page_end_writer_lock(const struct btrfs_fs_info *fs_info,
 		struct page *page, u64 start, u32 len)
 {
-	if (unlikely(!fs_info) || !btrfs_is_subpage(fs_info, page))
+	if (unlikely(!fs_info) || !btrfs_is_subpage(fs_info, page->mapping))
 		return unlock_page(page);
 	btrfs_subpage_clamp_range(page, &start, &len);
 	if (btrfs_subpage_end_and_test_writer(fs_info, page, start, len))
@@ -612,7 +607,8 @@ IMPLEMENT_BTRFS_SUBPAGE_TEST_OP(checked);
 void btrfs_page_set_##name(const struct btrfs_fs_info *fs_info,		\
 		struct page *page, u64 start, u32 len)			\
 {									\
-	if (unlikely(!fs_info) || !btrfs_is_subpage(fs_info, page)) {	\
+	if (unlikely(!fs_info) ||					\
+	    !btrfs_is_subpage(fs_info, page->mapping)) {		\
 		set_page_func(page);					\
 		return;							\
 	}								\
@@ -621,7 +617,8 @@ void btrfs_page_set_##name(const struct btrfs_fs_info *fs_info,		\
 void btrfs_page_clear_##name(const struct btrfs_fs_info *fs_info,	\
 		struct page *page, u64 start, u32 len)			\
 {									\
-	if (unlikely(!fs_info) || !btrfs_is_subpage(fs_info, page)) {	\
+	if (unlikely(!fs_info) ||					\
+	    !btrfs_is_subpage(fs_info, page->mapping)) {		\
 		clear_page_func(page);					\
 		return;							\
 	}								\
@@ -630,14 +627,16 @@ void btrfs_page_clear_##name(const struct btrfs_fs_info *fs_info,	\
 bool btrfs_page_test_##name(const struct btrfs_fs_info *fs_info,	\
 		struct page *page, u64 start, u32 len)			\
 {									\
-	if (unlikely(!fs_info) || !btrfs_is_subpage(fs_info, page))	\
+	if (unlikely(!fs_info) ||					\
+	    !btrfs_is_subpage(fs_info, page->mapping))			\
 		return test_page_func(page);				\
 	return btrfs_subpage_test_##name(fs_info, page, start, len);	\
 }									\
 void btrfs_page_clamp_set_##name(const struct btrfs_fs_info *fs_info,	\
 		struct page *page, u64 start, u32 len)			\
 {									\
-	if (unlikely(!fs_info) || !btrfs_is_subpage(fs_info, page)) {	\
+	if (unlikely(!fs_info) ||					\
+	    !btrfs_is_subpage(fs_info, page->mapping)) {	\
 		set_page_func(page);					\
 		return;							\
 	}								\
@@ -647,7 +646,8 @@ void btrfs_page_clamp_set_##name(const struct btrfs_fs_info *fs_info,	\
 void btrfs_page_clamp_clear_##name(const struct btrfs_fs_info *fs_info, \
 		struct page *page, u64 start, u32 len)			\
 {									\
-	if (unlikely(!fs_info) || !btrfs_is_subpage(fs_info, page)) {	\
+	if (unlikely(!fs_info) ||					\
+	    !btrfs_is_subpage(fs_info, page->mapping)) {		\
 		clear_page_func(page);					\
 		return;							\
 	}								\
@@ -657,7 +657,8 @@ void btrfs_page_clamp_clear_##name(const struct btrfs_fs_info *fs_info, \
 bool btrfs_page_clamp_test_##name(const struct btrfs_fs_info *fs_info,	\
 		struct page *page, u64 start, u32 len)			\
 {									\
-	if (unlikely(!fs_info) || !btrfs_is_subpage(fs_info, page))	\
+	if (unlikely(!fs_info) ||					\
+	    !btrfs_is_subpage(fs_info, page->mapping)) \
 		return test_page_func(page);				\
 	btrfs_subpage_clamp_range(page, &start, &len);			\
 	return btrfs_subpage_test_##name(fs_info, page, start, len);	\
@@ -686,7 +687,7 @@ void btrfs_page_assert_not_dirty(const struct btrfs_fs_info *fs_info,
 		return;
 
 	ASSERT(!PageDirty(page));
-	if (!btrfs_is_subpage(fs_info, page))
+	if (!btrfs_is_subpage(fs_info, page->mapping))
 		return;
 
 	ASSERT(folio_test_private(folio) && folio_get_private(folio));
@@ -716,7 +717,7 @@ void btrfs_page_unlock_writer(struct btrfs_fs_info *fs_info, struct page *page,
 
 	ASSERT(PageLocked(page));
 	/* For non-subpage case, we just unlock the page */
-	if (!btrfs_is_subpage(fs_info, page))
+	if (!btrfs_is_subpage(fs_info, page->mapping))
 		return unlock_page(page);
 
 	ASSERT(folio_test_private(folio) && folio_get_private(folio));