xfs: bugfixes for 3.8-rc6 - fix return value when filesystem probe finds no XFS magic, a regression introduced in 9802182. - fix stack switch in __xfs_bmapi_allocate by moving the check for stack switch up into xfs_bmapi_write. - fix oops in _xfs_buf_find by validating that the requested block is within the filesystem bounds. - limit speculative preallocation near ENOSPC. - fix an unmount hang in xfs_wait_buftarg by freeing the xfs_buf_log_item in xfs_buf_item_unlock. - fix a possible use after free with AIO. - fix xfs_swap_extents after removal of xfs_flushinval_pages, a regression introduced in fb59581404a.