btrfs: remove unused raid56 functions which were dedicated for scrub

Since the scrub rework, the following RAID56 functions are no longer
called:

- raid56_add_scrub_pages()
- raid56_alloc_missing_rbio()
- raid56_submit_missing_rbio()

Those functions are all utilized by scrub to handle missing device cases
for RAID56.

However the new scrub code handle them in a completely different way:

- If it's data stripe, go recovery path through btrfs_submit_bio()
- If it's P/Q stripe, it would be handled through
raid56_parity_submit_scrub_rbio()
And that function would handle dev-replace and repair properly.

Thus we can safely remove those functions.

Signed-off-by: Qu Wenruo <[e-mail]>
Reviewed-by: David Sterba <[e-mail]>
Signed-off-by: David Sterba <[e-mail]>

fs/btrfs/raid56.c

···
 	return rbio;
 }
 
-/* Used for both parity scrub and missing. */
-void raid56_add_scrub_pages(struct btrfs_raid_bio *rbio, struct page *page,
-			    unsigned int pgoff, u64 logical)
-{
-	const u32 sectorsize = rbio->bioc->fs_info->sectorsize;
-	int stripe_offset;
-	int index;
-
-	ASSERT(logical >= rbio->bioc->full_stripe_logical);
-	ASSERT(logical + sectorsize <= rbio->bioc->full_stripe_logical +
-				       BTRFS_STRIPE_LEN * rbio->nr_data);
-	stripe_offset = (int)(logical - rbio->bioc->full_stripe_logical);
-	index = stripe_offset / sectorsize;
-	rbio->bio_sectors[index].page = page;
-	rbio->bio_sectors[index].pgoff = pgoff;
-}
-
 /*
  * We just scrub the parity that we have correct data on the same horizontal,
  * so we needn't allocate all pages for all the stripes.
···
 {
 	if (!lock_stripe_add(rbio))
 		start_async_work(rbio, scrub_rbio_work_locked);
-}
-
-/* The following code is used for dev replace of a missing RAID 5/6 device. */
-
-struct btrfs_raid_bio *
-raid56_alloc_missing_rbio(struct bio *bio, struct btrfs_io_context *bioc)
-{
-	struct btrfs_fs_info *fs_info = bioc->fs_info;
-	struct btrfs_raid_bio *rbio;
-
-	rbio = alloc_rbio(fs_info, bioc);
-	if (IS_ERR(rbio))
-		return NULL;
-
-	rbio->operation = BTRFS_RBIO_REBUILD_MISSING;
-	bio_list_add(&rbio->bio_list, bio);
-	/*
-	 * This is a special bio which is used to hold the completion handler
-	 * and make the scrub rbio is similar to the other types
-	 */
-	ASSERT(!bio->bi_iter.bi_size);
-
-	set_rbio_range_error(rbio, bio);
-
-	return rbio;
-}
-
-void raid56_submit_missing_rbio(struct btrfs_raid_bio *rbio)
-{
-	start_async_work(rbio, recover_rbio_work);
 }

fs/btrfs/raid56.h

···
 			   int mirror_num);
 void raid56_parity_write(struct bio *bio, struct btrfs_io_context *bioc);
 
-void raid56_add_scrub_pages(struct btrfs_raid_bio *rbio, struct page *page,
-			    unsigned int pgoff, u64 logical);
-
 struct btrfs_raid_bio *raid56_parity_alloc_scrub_rbio(struct bio *bio,
 				struct btrfs_io_context *bioc,
 				struct btrfs_device *scrub_dev,
 				unsigned long *dbitmap, int stripe_nsectors);
 void raid56_parity_submit_scrub_rbio(struct btrfs_raid_bio *rbio);
-
-struct btrfs_raid_bio *
-raid56_alloc_missing_rbio(struct bio *bio, struct btrfs_io_context *bioc);
-void raid56_submit_missing_rbio(struct btrfs_raid_bio *rbio);
 
 int btrfs_alloc_stripe_hash_table(struct btrfs_fs_info *info);
 void btrfs_free_stripe_hash_table(struct btrfs_fs_info *info);