btrfs: unify to use writer locks for subpage locking

Since commit d7172f52e993 ("btrfs: use per-buffer locking for
extent_buffer reading"), metadata read no longer relies on the subpage
reader locking.

This means we do not need to maintain a different metadata/data split
for locking, so we can convert the existing reader lock users by:

- add_ra_bio_pages()
  Convert to btrfs_folio_set_writer_lock()

- end_folio_read()
  Convert to btrfs_folio_end_writer_lock()

- begin_folio_read()
  Convert to btrfs_folio_set_writer_lock()

- folio_range_has_eb()
  Remove the subpage->readers checks, since it is always 0.

- Remove btrfs_subpage_start_reader() and btrfs_subpage_end_reader()

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

1 files changed, 0 insertions, 13 deletions

diff --git a/fs/btrfs/subpage.h b/fs/btrfs/subpage.h
index e4076c5b06bc..c150aba9318e 100644
--- a/fs/btrfs/subpage.h
+++ b/fs/btrfs/subpage.h
@@ -45,14 +45,6 @@ enum {
 struct btrfs_subpage {
 	/* Common members for both data and metadata pages */
 	spinlock_t lock;
-	/*
-	 * Both data and metadata needs to track how many readers are for the
-	 * page.
-	 * Data relies on @readers to unlock the page when last reader finished.
-	 * While metadata doesn't need page unlock, it needs to prevent
-	 * page::private get cleared before the last end_page_read().
-	 */
-	atomic_t readers;
 	union {
 		/*
 		 * Structures only used by metadata
@@ -95,11 +87,6 @@ void btrfs_free_subpage(struct btrfs_subpage *subpage);
 void btrfs_folio_inc_eb_refs(const struct btrfs_fs_info *fs_info, struct folio *folio);
 void btrfs_folio_dec_eb_refs(const struct btrfs_fs_info *fs_info, struct folio *folio);
 
-void btrfs_subpage_start_reader(const struct btrfs_fs_info *fs_info,
-				struct folio *folio, u64 start, u32 len);
-void btrfs_subpage_end_reader(const struct btrfs_fs_info *fs_info,
-			      struct folio *folio, u64 start, u32 len);
-
 void btrfs_folio_end_writer_lock(const struct btrfs_fs_info *fs_info,
 				 struct folio *folio, u64 start, u32 len);
 void btrfs_folio_set_writer_lock(const struct btrfs_fs_info *fs_info,