btrfs: remove btrfs_folio_end_all_writers()

The function btrfs_folio_end_all_writers() is only utilized in
extent_writepage() as a way to unlock all subpage range (for both
successful submission and error handling).

Meanwhile we have a similar function, btrfs_folio_end_writer_lock().

The difference is, btrfs_folio_end_writer_lock() expects a range that is
a subset of the already locked range.

This limit on btrfs_folio_end_writer_lock() is a little overkilled,
preventing it from being utilized for error paths.

So here we enhance btrfs_folio_end_writer_lock() to accept a superset of
the locked range, and only end the locked subset.
This means we can replace btrfs_folio_end_all_writers() with
btrfs_folio_end_writer_lock() instead.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/extent_io.c

@@ -1466,7 +1466,8 @@ static int extent_writepage(struct folio *folio, struct btrfs_bio_ctrl *bio_ctrl
 		mapping_set_error(folio->mapping, ret);
 	}
 
-	btrfs_folio_end_all_writers(inode_to_fs_info(inode), folio);
+	btrfs_folio_end_writer_lock(inode_to_fs_info(inode), folio,
+				    page_start, PAGE_SIZE);
 	ASSERT(ret <= 0);
 	return ret;
 }

fs/btrfs/subpage.c

@@ -322,6 +322,8 @@ static bool btrfs_subpage_end_and_test_writer(const struct btrfs_fs_info *fs_inf
 	const int start_bit = subpage_calc_start_bit(fs_info, folio, locked, start, len);
 	const int nbits = (len >> fs_info->sectorsize_bits);
 	unsigned long flags;
+	unsigned int cleared = 0;
+	int bit = start_bit;
 	bool last;
 
 	btrfs_subpage_assert(fs_info, folio, start, len);
@@ -339,11 +341,12 @@ static bool btrfs_subpage_end_and_test_writer(const struct btrfs_fs_info *fs_inf
 		return true;
 	}
 
-	ASSERT(atomic_read(&subpage->writers) >= nbits);
-	/* The target range should have been locked. */
-	ASSERT(bitmap_test_range_all_set(subpage->bitmaps, start_bit, nbits));
-	bitmap_clear(subpage->bitmaps, start_bit, nbits);
-	last = atomic_sub_and_test(nbits, &subpage->writers);
+	for_each_set_bit_from(bit, subpage->bitmaps, start_bit + nbits) {
+		clear_bit(bit, subpage->bitmaps);
+		cleared++;
+	}
+	ASSERT(atomic_read(&subpage->writers) >= cleared);
+	last = atomic_sub_and_test(cleared, &subpage->writers);
 	spin_unlock_irqrestore(&subpage->lock, flags);
 	return last;
 }
@@ -825,50 +828,6 @@ bool btrfs_subpage_find_writer_locked(const struct btrfs_fs_info *fs_info,
 	return found;
 }
 
-/*
- * Unlike btrfs_folio_end_writer_lock() which unlocks a specified subpage range,
- * this ends all writer locked ranges of a page.
- *
- * This is for the locked page of extent_writepage(), as the locked page
- * can contain several locked subpage ranges.
- */
-void btrfs_folio_end_all_writers(const struct btrfs_fs_info *fs_info, struct folio *folio)
-{
-	struct btrfs_subpage *subpage = folio_get_private(folio);
-	u64 folio_start = folio_pos(folio);
-	u64 cur = folio_start;
-
-	ASSERT(folio_test_locked(folio));
-	if (!btrfs_is_subpage(fs_info, folio->mapping)) {
-		folio_unlock(folio);
-		return;
-	}
-
-	/* The page has no new delalloc range locked on it. Just plain unlock. */
-	if (atomic_read(&subpage->writers) == 0) {
-		folio_unlock(folio);
-		return;
-	}
-	while (cur < folio_start + PAGE_SIZE) {
-		u64 found_start;
-		u32 found_len;
-		bool found;
-		bool last;
-
-		found = btrfs_subpage_find_writer_locked(fs_info, folio, cur,
-							 &found_start, &found_len);
-		if (!found)
-			break;
-		last = btrfs_subpage_end_and_test_writer(fs_info, folio,
-							 found_start, found_len);
-		if (last) {
-			folio_unlock(folio);
-			break;
-		}
-		cur = found_start + found_len;
-	}
-}
-
 #define GET_SUBPAGE_BITMAP(subpage, fs_info, name, dst)			\
 {									\
 	const int sectors_per_page = fs_info->sectors_per_page;		\

fs/btrfs/subpage.h

@@ -109,7 +109,6 @@ void btrfs_folio_set_writer_lock(const struct btrfs_fs_info *fs_info,
 bool btrfs_subpage_find_writer_locked(const struct btrfs_fs_info *fs_info,
 				      struct folio *folio, u64 search_start,
 				      u64 *found_start_ret, u32 *found_len_ret);
-void btrfs_folio_end_all_writers(const struct btrfs_fs_info *fs_info, struct folio *folio);
 
 /*
  * Template for subpage related operations.