btrfs: replace btrfs_io_bio::end_io with a simple helper

The end_io callback implemented as btrfs_io_bio_endio_readpage only
calls kfree. Also the callback is set only in case the csum buffer is
allocated and not pointing to the inline buffer. We can use that
information to drop the indirection and call a helper that will free the
csums only in the right case.

This shrinks struct btrfs_io_bio by 8 bytes.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/extent_io.c

@@ -2623,8 +2623,7 @@ static void end_bio_extent_readpage(struct bio *bio)
 	if (extent_len)
 		endio_readpage_release_extent(tree, extent_start, extent_len,
 					      uptodate);
-	if (io_bio->end_io)
-		io_bio->end_io(io_bio, blk_status_to_errno(bio->bi_status));
+	btrfs_io_bio_free_csum(io_bio);
 	bio_put(bio);
 }
 

fs/btrfs/file-item.c

@@ -142,14 +142,6 @@ int btrfs_lookup_file_extent(struct btrfs_trans_handle *trans,
 	return ret;
 }
 
-static void btrfs_io_bio_endio_readpage(struct btrfs_io_bio *bio, int err)
-{
-	if (bio->csum != bio->csum_inline) {
-		kfree(bio->csum);
-		bio->csum = NULL;
-	}
-}
-
 static blk_status_t __btrfs_lookup_bio_sums(struct inode *inode, struct bio *bio,
 				   u64 logical_offset, u32 *dst, int dio)
 {
@@ -184,7 +176,6 @@ static blk_status_t __btrfs_lookup_bio_sums(struct inode *inode, struct bio *bio
 				btrfs_free_path(path);
 				return BLK_STS_RESOURCE;
 			}
-			btrfs_bio->end_io = btrfs_io_bio_endio_readpage;
 		} else {
 			btrfs_bio->csum = btrfs_bio->csum_inline;
 		}

fs/btrfs/inode.c

@@ -8017,9 +8017,7 @@ static void btrfs_endio_direct_read(struct bio *bio)
 
 	dio_bio->bi_status = err;
 	dio_end_io(dio_bio);
-
-	if (io_bio->end_io)
-		io_bio->end_io(io_bio, blk_status_to_errno(err));
+	btrfs_io_bio_free_csum(io_bio);
 	bio_put(bio);
 }
 
@@ -8372,8 +8370,7 @@ static void btrfs_submit_direct(struct bio *dio_bio, struct inode *inode,
 	if (!ret)
 		return;
 
-	if (io_bio->end_io)
-		io_bio->end_io(io_bio, ret);
+	btrfs_io_bio_free_csum(io_bio);
 
 free_ordered:
 	/*

fs/btrfs/volumes.h

@@ -267,14 +267,12 @@ struct btrfs_fs_devices {
  * we allocate are actually btrfs_io_bios.  We'll cram as much of
  * struct btrfs_bio as we can into this over time.
  */
-typedef void (btrfs_io_bio_end_io_t) (struct btrfs_io_bio *bio, int err);
 struct btrfs_io_bio {
 	unsigned int mirror_num;
 	unsigned int stripe_index;
 	u64 logical;
 	u8 *csum;
 	u8 csum_inline[BTRFS_BIO_INLINE_CSUM_SIZE];
-	btrfs_io_bio_end_io_t *end_io;
 	struct bvec_iter iter;
 	/*
 	 * This member must come last, bio_alloc_bioset will allocate enough
@@ -288,6 +286,14 @@ static inline struct btrfs_io_bio *btrfs_io_bio(struct bio *bio)
 	return container_of(bio, struct btrfs_io_bio, bio);
 }
 
+static inline void btrfs_io_bio_free_csum(struct btrfs_io_bio *io_bio)
+{
+	if (io_bio->csum != io_bio->csum_inline) {
+		kfree(io_bio->csum);
+		io_bio->csum = NULL;
+	}
+}
+
 struct btrfs_bio_stripe {
 	struct btrfs_device *dev;
 	u64 physical;