btrfs: remove the direct I/O read checksum lookup optimization

To prepare for pending changes drop the optimization to only look up
csums once per bio that is submitted from the iomap layer.  In the
short run this does cause additional lookups for fragmented direct
reads, but later in the series, the bio based lookup will be used on
the entire bio submitted from iomap, restoring the old behavior
in common code.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/inode.c

@@ -100,9 +100,6 @@ struct btrfs_dio_private {
 	 */
 	refcount_t refs;
 
-	/* Array of checksums */
-	u8 *csums;
-
 	/* This must be last */
 	struct bio bio;
 };
@@ -7907,7 +7904,6 @@ static void btrfs_dio_private_put(struct btrfs_dio_private *dip)
 			      dip->file_offset + dip->bytes - 1, NULL);
 	}
 
-	kfree(dip->csums);
 	bio_endio(&dip->bio);
 }
 
@@ -7990,7 +7986,6 @@ static void btrfs_submit_dio_bio(struct bio *bio, struct btrfs_inode *inode,
 				 u64 file_offset, int async_submit)
 {
 	struct btrfs_fs_info *fs_info = inode->root->fs_info;
-	struct btrfs_dio_private *dip = btrfs_bio(bio)->private;
 	blk_status_t ret;
 
 	/* Save the original iter for read repair */
@@ -8017,8 +8012,11 @@ static void btrfs_submit_dio_bio(struct bio *bio, struct btrfs_inode *inode,
 			return;
 		}
 	} else {
-		btrfs_bio(bio)->csum = btrfs_csum_ptr(fs_info, dip->csums,
-						      file_offset - dip->file_offset);
+		ret = btrfs_lookup_bio_sums(&inode->vfs_inode, bio, NULL);
+		if (ret) {
+			btrfs_bio_end_io(btrfs_bio(bio), ret);
+			return;
+		}
 	}
 map:
 	btrfs_submit_bio(fs_info, bio, 0);
@@ -8030,7 +8028,6 @@ static void btrfs_submit_direct(const struct iomap_iter *iter,
 	struct btrfs_dio_private *dip =
 		container_of(dio_bio, struct btrfs_dio_private, bio);
 	struct inode *inode = iter->inode;
-	const bool write = (btrfs_op(dio_bio) == BTRFS_MAP_WRITE);
 	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
 	const bool raid56 = (btrfs_data_alloc_profile(fs_info) &
 			     BTRFS_BLOCK_GROUP_RAID56_MASK);
@@ -8051,25 +8048,6 @@ static void btrfs_submit_direct(const struct iomap_iter *iter,
 	dip->file_offset = file_offset;
 	dip->bytes = dio_bio->bi_iter.bi_size;
 	refcount_set(&dip->refs, 1);
-	dip->csums = NULL;
-
-	if (!write && !(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) {
-		unsigned int nr_sectors =
-			(dio_bio->bi_iter.bi_size >> fs_info->sectorsize_bits);
-
-		/*
-		 * Load the csums up front to reduce csum tree searches and
-		 * contention when submitting bios.
-		 */
-		status = BLK_STS_RESOURCE;
-		dip->csums = kcalloc(nr_sectors, fs_info->csum_size, GFP_NOFS);
-		if (!dip->csums)
-			goto out_err;
-
-		status = btrfs_lookup_bio_sums(inode, dio_bio, dip->csums);
-		if (status != BLK_STS_OK)
-			goto out_err;
-	}
 
 	start_sector = dio_bio->bi_iter.bi_sector;
 	submit_len = dio_bio->bi_iter.bi_size;