ocfs2: btree support for removal of arbirtrary extents

Add code to the btree paths to support the removal of arbitrary regions
within an existing extent. With proper higher level support this can be used
to "punch holes" in a file. Truncate (a special case of hole punching) could
also be converted to use these methods.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>

fs/ocfs2/alloc.c

@@ -4139,6 +4139,373 @@ out:
 	return ret;
 }
 
+static int ocfs2_split_tree(struct inode *inode, struct buffer_head *di_bh,
+			    handle_t *handle, struct ocfs2_path *path,
+			    int index, u32 new_range,
+			    struct ocfs2_alloc_context *meta_ac)
+{
+	int ret, depth, credits = handle->h_buffer_credits;
+	struct ocfs2_dinode *di = (struct ocfs2_dinode *)di_bh->b_data;
+	struct buffer_head *last_eb_bh = NULL;
+	struct ocfs2_extent_block *eb;
+	struct ocfs2_extent_list *rightmost_el, *el;
+	struct ocfs2_extent_rec split_rec;
+	struct ocfs2_extent_rec *rec;
+	struct ocfs2_insert_type insert;
+
+	/*
+	 * Setup the record to split before we grow the tree.
+	 */
+	el = path_leaf_el(path);
+	rec = &el->l_recs[index];
+	ocfs2_make_right_split_rec(inode->i_sb, &split_rec, new_range, rec);
+
+	depth = path->p_tree_depth;
+	if (depth > 0) {
+		ret = ocfs2_read_block(OCFS2_SB(inode->i_sb),
+				       le64_to_cpu(di->i_last_eb_blk),
+				       &last_eb_bh, OCFS2_BH_CACHED, inode);
+		if (ret < 0) {
+			mlog_errno(ret);
+			goto out;
+		}
+
+		eb = (struct ocfs2_extent_block *) last_eb_bh->b_data;
+		rightmost_el = &eb->h_list;
+	} else
+		rightmost_el = path_leaf_el(path);
+
+	credits += path->p_tree_depth + ocfs2_extend_meta_needed(di);
+	ret = ocfs2_extend_trans(handle, credits);
+	if (ret) {
+		mlog_errno(ret);
+		goto out;
+	}
+
+	if (le16_to_cpu(rightmost_el->l_next_free_rec) ==
+	    le16_to_cpu(rightmost_el->l_count)) {
+		int old_depth = depth;
+
+		ret = ocfs2_grow_tree(inode, handle, di_bh, &depth, &last_eb_bh,
+				      meta_ac);
+		if (ret) {
+			mlog_errno(ret);
+			goto out;
+		}
+
+		if (old_depth != depth) {
+			eb = (struct ocfs2_extent_block *)last_eb_bh->b_data;
+			rightmost_el = &eb->h_list;
+		}
+	}
+
+	memset(&insert, 0, sizeof(struct ocfs2_insert_type));
+	insert.ins_appending = APPEND_NONE;
+	insert.ins_contig = CONTIG_NONE;
+	insert.ins_split = SPLIT_RIGHT;
+	insert.ins_free_records = le16_to_cpu(rightmost_el->l_count)
+		- le16_to_cpu(rightmost_el->l_next_free_rec);
+	insert.ins_tree_depth = depth;
+
+	ret = ocfs2_do_insert_extent(inode, handle, di_bh, &split_rec, &insert);
+	if (ret)
+		mlog_errno(ret);
+
+out:
+	brelse(last_eb_bh);
+	return ret;
+}
+
+static int ocfs2_truncate_rec(struct inode *inode, handle_t *handle,
+			      struct ocfs2_path *path, int index,
+			      struct ocfs2_cached_dealloc_ctxt *dealloc,
+			      u32 cpos, u32 len)
+{
+	int ret;
+	u32 left_cpos, rec_range, trunc_range;
+	int wants_rotate = 0, is_rightmost_tree_rec = 0;
+	struct super_block *sb = inode->i_sb;
+	struct ocfs2_path *left_path = NULL;
+	struct ocfs2_extent_list *el = path_leaf_el(path);
+	struct ocfs2_extent_rec *rec;
+	struct ocfs2_extent_block *eb;
+
+	if (ocfs2_is_empty_extent(&el->l_recs[0]) && index > 0) {
+		ret = ocfs2_rotate_tree_left(inode, handle, path, dealloc);
+		if (ret) {
+			mlog_errno(ret);
+			goto out;
+		}
+
+		index--;
+	}
+
+	if (index == (le16_to_cpu(el->l_next_free_rec) - 1) &&
+	    path->p_tree_depth) {
+		/*
+		 * Check whether this is the rightmost tree record. If
+		 * we remove all of this record or part of its right
+		 * edge then an update of the record lengths above it
+		 * will be required.
+		 */
+		eb = (struct ocfs2_extent_block *)path_leaf_bh(path)->b_data;
+		if (eb->h_next_leaf_blk == 0)
+			is_rightmost_tree_rec = 1;
+	}
+
+	rec = &el->l_recs[index];
+	if (index == 0 && path->p_tree_depth &&
+	    le32_to_cpu(rec->e_cpos) == cpos) {
+		/*
+		 * Changing the leftmost offset (via partial or whole
+		 * record truncate) of an interior (or rightmost) path
+		 * means we have to update the subtree that is formed
+		 * by this leaf and the one to it's left.
+		 *
+		 * There are two cases we can skip:
+		 *   1) Path is the leftmost one in our inode tree.
+		 *   2) The leaf is rightmost and will be empty after
+		 *      we remove the extent record - the rotate code
+		 *      knows how to update the newly formed edge.
+		 */
+
+		ret = ocfs2_find_cpos_for_left_leaf(inode->i_sb, path,
+						    &left_cpos);
+		if (ret) {
+			mlog_errno(ret);
+			goto out;
+		}
+
+		if (left_cpos && le16_to_cpu(el->l_next_free_rec) > 1) {
+			left_path = ocfs2_new_path(path_root_bh(path),
+						   path_root_el(path));
+			if (!left_path) {
+				ret = -ENOMEM;
+				mlog_errno(ret);
+				goto out;
+			}
+
+			ret = ocfs2_find_path(inode, left_path, left_cpos);
+			if (ret) {
+				mlog_errno(ret);
+				goto out;
+			}
+		}
+	}
+
+	ret = ocfs2_extend_rotate_transaction(handle, 0,
+					      handle->h_buffer_credits,
+					      path);
+	if (ret) {
+		mlog_errno(ret);
+		goto out;
+	}
+
+	ret = ocfs2_journal_access_path(inode, handle, path);
+	if (ret) {
+		mlog_errno(ret);
+		goto out;
+	}
+
+	ret = ocfs2_journal_access_path(inode, handle, left_path);
+	if (ret) {
+		mlog_errno(ret);
+		goto out;
+	}
+
+	rec_range = le32_to_cpu(rec->e_cpos) + ocfs2_rec_clusters(el, rec);
+	trunc_range = cpos + len;
+
+	if (le32_to_cpu(rec->e_cpos) == cpos && rec_range == trunc_range) {
+		int next_free;
+
+		memset(rec, 0, sizeof(*rec));
+		ocfs2_cleanup_merge(el, index);
+		wants_rotate = 1;
+
+		next_free = le16_to_cpu(el->l_next_free_rec);
+		if (is_rightmost_tree_rec && next_free > 1) {
+			/*
+			 * We skip the edge update if this path will
+			 * be deleted by the rotate code.
+			 */
+			rec = &el->l_recs[next_free - 1];
+			ocfs2_adjust_rightmost_records(inode, handle, path,
+						       rec);
+		}
+	} else if (le32_to_cpu(rec->e_cpos) == cpos) {
+		/* Remove leftmost portion of the record. */
+		le32_add_cpu(&rec->e_cpos, len);
+		le64_add_cpu(&rec->e_blkno, ocfs2_clusters_to_blocks(sb, len));
+		le16_add_cpu(&rec->e_leaf_clusters, -len);
+	} else if (rec_range == trunc_range) {
+		/* Remove rightmost portion of the record */
+		le16_add_cpu(&rec->e_leaf_clusters, -len);
+		if (is_rightmost_tree_rec)
+			ocfs2_adjust_rightmost_records(inode, handle, path, rec);
+	} else {
+		/* Caller should have trapped this. */
+		mlog(ML_ERROR, "Inode %llu: Invalid record truncate: (%u, %u) "
+		     "(%u, %u)\n", (unsigned long long)OCFS2_I(inode)->ip_blkno,
+		     le32_to_cpu(rec->e_cpos),
+		     le16_to_cpu(rec->e_leaf_clusters), cpos, len);
+		BUG();
+	}
+
+	if (left_path) {
+		int subtree_index;
+
+		subtree_index = ocfs2_find_subtree_root(inode, left_path, path);
+		ocfs2_complete_edge_insert(inode, handle, left_path, path,
+					   subtree_index);
+	}
+
+	ocfs2_journal_dirty(handle, path_leaf_bh(path));
+
+	ret = ocfs2_rotate_tree_left(inode, handle, path, dealloc);
+	if (ret) {
+		mlog_errno(ret);
+		goto out;
+	}
+
+out:
+	ocfs2_free_path(left_path);
+	return ret;
+}
+
+static int ocfs2_remove_extent(struct inode *inode, struct buffer_head *di_bh,
+			       u32 cpos, u32 len, handle_t *handle,
+			       struct ocfs2_alloc_context *meta_ac,
+			       struct ocfs2_cached_dealloc_ctxt *dealloc)
+{
+	int ret, index;
+	u32 rec_range, trunc_range;
+	struct ocfs2_extent_rec *rec;
+	struct ocfs2_extent_list *el;
+	struct ocfs2_path *path;
+
+	ocfs2_extent_map_trunc(inode, 0);
+
+	path = ocfs2_new_inode_path(di_bh);
+	if (!path) {
+		ret = -ENOMEM;
+		mlog_errno(ret);
+		goto out;
+	}
+
+	ret = ocfs2_find_path(inode, path, cpos);
+	if (ret) {
+		mlog_errno(ret);
+		goto out;
+	}
+
+	el = path_leaf_el(path);
+	index = ocfs2_search_extent_list(el, cpos);
+	if (index == -1 || index >= le16_to_cpu(el->l_next_free_rec)) {
+		ocfs2_error(inode->i_sb,
+			    "Inode %llu has an extent at cpos %u which can no "
+			    "longer be found.\n",
+			    (unsigned long long)OCFS2_I(inode)->ip_blkno, cpos);
+		ret = -EROFS;
+		goto out;
+	}
+
+	/*
+	 * We have 3 cases of extent removal:
+	 *   1) Range covers the entire extent rec
+	 *   2) Range begins or ends on one edge of the extent rec
+	 *   3) Range is in the middle of the extent rec (no shared edges)
+	 *
+	 * For case 1 we remove the extent rec and left rotate to
+	 * fill the hole.
+	 *
+	 * For case 2 we just shrink the existing extent rec, with a
+	 * tree update if the shrinking edge is also the edge of an
+	 * extent block.
+	 *
+	 * For case 3 we do a right split to turn the extent rec into
+	 * something case 2 can handle.
+	 */
+	rec = &el->l_recs[index];
+	rec_range = le32_to_cpu(rec->e_cpos) + ocfs2_rec_clusters(el, rec);
+	trunc_range = cpos + len;
+
+	BUG_ON(cpos < le32_to_cpu(rec->e_cpos) || trunc_range > rec_range);
+
+	mlog(0, "Inode %llu, remove (cpos %u, len %u). Existing index %d "
+	     "(cpos %u, len %u)\n",
+	     (unsigned long long)OCFS2_I(inode)->ip_blkno, cpos, len, index,
+	     le32_to_cpu(rec->e_cpos), ocfs2_rec_clusters(el, rec));
+
+	if (le32_to_cpu(rec->e_cpos) == cpos || rec_range == trunc_range) {
+		ret = ocfs2_truncate_rec(inode, handle, path, index, dealloc,
+					 cpos, len);
+		if (ret) {
+			mlog_errno(ret);
+			goto out;
+		}
+	} else {
+		ret = ocfs2_split_tree(inode, di_bh, handle, path, index,
+				       trunc_range, meta_ac);
+		if (ret) {
+			mlog_errno(ret);
+			goto out;
+		}
+
+		/*
+		 * The split could have manipulated the tree enough to
+		 * move the record location, so we have to look for it again.
+		 */
+		ocfs2_reinit_path(path, 1);
+
+		ret = ocfs2_find_path(inode, path, cpos);
+		if (ret) {
+			mlog_errno(ret);
+			goto out;
+		}
+
+		el = path_leaf_el(path);
+		index = ocfs2_search_extent_list(el, cpos);
+		if (index == -1 || index >= le16_to_cpu(el->l_next_free_rec)) {
+			ocfs2_error(inode->i_sb,
+				    "Inode %llu: split at cpos %u lost record.",
+				    (unsigned long long)OCFS2_I(inode)->ip_blkno,
+				    cpos);
+			ret = -EROFS;
+			goto out;
+		}
+
+		/*
+		 * Double check our values here. If anything is fishy,
+		 * it's easier to catch it at the top level.
+		 */
+		rec = &el->l_recs[index];
+		rec_range = le32_to_cpu(rec->e_cpos) +
+			ocfs2_rec_clusters(el, rec);
+		if (rec_range != trunc_range) {
+			ocfs2_error(inode->i_sb,
+				    "Inode %llu: error after split at cpos %u"
+				    "trunc len %u, existing record is (%u,%u)",
+				    (unsigned long long)OCFS2_I(inode)->ip_blkno,
+				    cpos, len, le32_to_cpu(rec->e_cpos),
+				    ocfs2_rec_clusters(el, rec));
+			ret = -EROFS;
+			goto out;
+		}
+
+		ret = ocfs2_truncate_rec(inode, handle, path, index, dealloc,
+					 cpos, len);
+		if (ret) {
+			mlog_errno(ret);
+			goto out;
+		}
+	}
+
+out:
+	ocfs2_free_path(path);
+	return ret;
+}
+
 static inline int ocfs2_truncate_log_needs_flush(struct ocfs2_super *osb)
 {
 	struct buffer_head *tl_bh = osb->osb_tl_bh;