Quoting Tvrtko Ursulin (2019-03-14 11:33:43) > I am only wondering what happens to reads/write to the trailing area? > Does shmemfs expands the backing store for this mmap and we just end up > with otherwise unused chunk at the end? My expectation would be that they generate a SIGBUS since the filp should not be extended to cover the absent pages. So it would be the equivalent of mmaping a file then calling ftruncate(0). I admit it's not obvious if shmem_getpage_gfp (backing shmem_fault) would prevent allocation of fresh backing pages beyond the initial filp size. Afaict, we would end up at alloc_page_vma() without rejecting an index beyond the end of the file. -Chris
