btrfs: Remove redundant bio_get/set calls in compressed read/write paths

bio_get/set is necessary only if the bio is going to be referenced
following submissions. In the code paths where such calls are made
we don't really need them since the bio is referenced only if
btrfs_map_bio returns an error. And this function can return an error
prior to submission only. So referencing the bio is safe. Furthermore
we do call bio_endio which will consume the last reference. So let's
remove the redundant calls.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/compression.c

@@ -362,8 +362,6 @@ blk_status_t btrfs_submit_compressed_write(struct inode *inode, u64 start,
 		page->mapping = NULL;
 		if (submit || bio_add_page(bio, page, PAGE_SIZE, 0) <
 		    PAGE_SIZE) {
-			bio_get(bio);
-
 			/*
 			 * inc the count before we submit the bio so
 			 * we know the end IO handler won't happen before
@@ -386,8 +384,6 @@ blk_status_t btrfs_submit_compressed_write(struct inode *inode, u64 start,
 				bio_endio(bio);
 			}
 
-			bio_put(bio);
-
 			bio = btrfs_bio_alloc(bdev, first_byte);
 			bio->bi_opf = REQ_OP_WRITE | write_flags;
 			bio->bi_private = cb;
@@ -403,7 +399,6 @@ blk_status_t btrfs_submit_compressed_write(struct inode *inode, u64 start,
 		first_byte += PAGE_SIZE;
 		cond_resched();
 	}
-	bio_get(bio);
 
 	ret = btrfs_bio_wq_end_io(fs_info, bio, BTRFS_WQ_ENDIO_DATA);
 	BUG_ON(ret); /* -ENOMEM */
@@ -419,7 +414,6 @@ blk_status_t btrfs_submit_compressed_write(struct inode *inode, u64 start,
 		bio_endio(bio);
 	}
 
-	bio_put(bio);
 	return 0;
 }
 
@@ -652,8 +646,6 @@ blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
 		page->mapping = NULL;
 		if (submit || bio_add_page(comp_bio, page, PAGE_SIZE, 0) <
 		    PAGE_SIZE) {
-			bio_get(comp_bio);
-
 			ret = btrfs_bio_wq_end_io(fs_info, comp_bio,
 						  BTRFS_WQ_ENDIO_DATA);
 			BUG_ON(ret); /* -ENOMEM */
@@ -680,8 +672,6 @@ blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
 				bio_endio(comp_bio);
 			}
 
-			bio_put(comp_bio);
-
 			comp_bio = btrfs_bio_alloc(bdev, cur_disk_byte);
 			bio_set_op_attrs(comp_bio, REQ_OP_READ, 0);
 			comp_bio->bi_private = cb;
@@ -691,7 +681,6 @@ blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
 		}
 		cur_disk_byte += PAGE_SIZE;
 	}
-	bio_get(comp_bio);
 
 	ret = btrfs_bio_wq_end_io(fs_info, comp_bio, BTRFS_WQ_ENDIO_DATA);
 	BUG_ON(ret); /* -ENOMEM */
@@ -707,7 +696,6 @@ blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
 		bio_endio(comp_bio);
 	}
 
-	bio_put(comp_bio);
 	return 0;
 
 fail2: