Btrfs: Lookup readpage checksums on bio submission again

This optimization had been removed because I thought it was triggering
csum errors.  The real cause of the errors was elsewhere, and so
this optimization is back.
Signed-off-by: Chris Mason <chris.mason@oracle.com>

fs/btrfs/file-item.c

@@ -134,7 +134,6 @@ int btrfs_lookup_file_extent(struct btrfs_trans_handle *trans,
 	return ret;
 }
 
-#if 0 /* broken */
 int btrfs_lookup_bio_sums(struct btrfs_root *root, struct inode *inode,
 			  struct bio *bio)
 {
@@ -151,6 +150,8 @@ int btrfs_lookup_bio_sums(struct btrfs_root *root, struct inode *inode,
 	struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
 
 	path = btrfs_alloc_path();
+	if (bio->bi_size > PAGE_CACHE_SIZE * 8)
+		path->reada = 2;
 
 	WARN_ON(bio->bi_vcnt <= 0);
 
@@ -211,7 +212,6 @@ found:
 	btrfs_free_path(path);
 	return 0;
 }
-#endif
 
 int btrfs_csum_one_bio(struct btrfs_root *root, struct inode *inode,
 		       struct bio *bio)

fs/btrfs/inode.c

@@ -389,15 +389,15 @@ int btrfs_submit_bio_hook(struct inode *inode, int rw, struct bio *bio,
 	ret = btrfs_bio_wq_end_io(root->fs_info, bio, 0);
 	BUG_ON(ret);
 
-	if (!(rw & (1 << BIO_RW))) {
-		goto mapit;
-	}
-
 	if (btrfs_test_opt(root, NODATASUM) ||
 	    btrfs_test_flag(inode, NODATASUM)) {
 		goto mapit;
 	}
 
+	if (!(rw & (1 << BIO_RW))) {
+		btrfs_lookup_bio_sums(root, inode, bio);
+		goto mapit;
+	}
 	return btrfs_wq_submit_bio(BTRFS_I(inode)->root->fs_info,
 				   inode, rw, bio, mirror_num,
 				   __btrfs_submit_bio_hook);
@@ -603,59 +603,6 @@ int btrfs_writepage_end_io_hook(struct page *page, u64 start, u64 end,
 	return btrfs_finish_ordered_io(page->mapping->host, start, end);
 }
 
-int btrfs_readpage_io_hook(struct page *page, u64 start, u64 end)
-{
-	int ret = 0;
-	struct inode *inode = page->mapping->host;
-	struct btrfs_root *root = BTRFS_I(inode)->root;
-	struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
-	struct btrfs_csum_item *item;
-	struct btrfs_path *path = NULL;
-	u32 csum;
-
-	if (btrfs_test_opt(root, NODATASUM) ||
-	    btrfs_test_flag(inode, NODATASUM))
-		return 0;
-
-	/*
-	 * It is possible there is an ordered extent that has
-	 * not yet finished for this range in the file.  If so,
-	 * that extent will have a csum cached, and it will insert
-	 * the sum after all the blocks in the extent are fully
-	 * on disk.  So, look for an ordered extent and use the
-	 * sum if found.  We have to do this before looking in the
-	 * btree because csum items are pre-inserted based on
-	 * the file size.  btrfs_lookup_csum might find an item
-	 * that still hasn't been fully filled.
-	 */
-	ret = btrfs_find_ordered_sum(inode, start, &csum);
-	if (ret == 0)
-		goto found;
-
-	ret = 0;
-	path = btrfs_alloc_path();
-	item = btrfs_lookup_csum(NULL, root, path, inode->i_ino, start, 0);
-	if (IS_ERR(item)) {
-		ret = PTR_ERR(item);
-		/* a csum that isn't present is a preallocated region. */
-		if (ret == -ENOENT || ret == -EFBIG)
-			ret = 0;
-		csum = 0;
-		if (printk_ratelimit())
-			printk("no csum found for inode %lu start %Lu\n", inode->i_ino,
-			       start);
-		goto out;
-	}
-	read_extent_buffer(path->nodes[0], &csum, (unsigned long)item,
-			   BTRFS_CRC32_SIZE);
-found:
-	set_state_private(io_tree, start, csum);
-out:
-	if (path)
-		btrfs_free_path(path);
-	return ret;
-}
-
 struct io_failure_record {
 	struct page *page;
 	u64 start;
@@ -3669,7 +3616,6 @@ static struct extent_io_ops btrfs_extent_io_ops = {
 	.fill_delalloc = run_delalloc_range,
 	.submit_bio_hook = btrfs_submit_bio_hook,
 	.merge_bio_hook = btrfs_merge_bio_hook,
-	.readpage_io_hook = btrfs_readpage_io_hook,
 	.readpage_end_io_hook = btrfs_readpage_end_io_hook,
 	.writepage_end_io_hook = btrfs_writepage_end_io_hook,
 	.writepage_start_hook = btrfs_writepage_start_hook,