!9549 btrfs: fix crash on racing fsync and size-extending write into prealloc

			path->slots[0]++;

			continue;

		}

		if (!dropped_extents) {

		/*

			 * Avoid logging extent items logged in past fsync calls

			 * and leading to duplicate keys in the log tree.

		 * Avoid overlapping items in the log tree. The first time we

		 * get here, get rid of everything from a past fsync. After

		 * that, if the current extent starts before the end of the last

		 * extent we copied, truncate the last one. This can happen if

		 * an ordered extent completion modifies the subvolume tree

		 * while btrfs_next_leaf() has the tree unlocked.

		 */

		if (!dropped_extents || key.offset < truncate_offset) {

			ret = truncate_inode_items(trans, root->log_root, inode,

						   truncate_offset,

						   min(key.offset, truncate_offset),

						   BTRFS_EXTENT_DATA_KEY);

			if (ret)

				goto out;

			dropped_extents = true;

		}

		truncate_offset = btrfs_file_extent_end(path);

		if (ins_nr == 0)

			start_slot = slot;

		ins_nr++;