Re: [PATCH hotfix 6.12 v3 4/5] mm: refactor arch_validate_flags() and arm64 MTE handling

[Lorenzo Stoakes]

On Tue, Oct 29, 2024 at 08:43:04AM -0700, Yang Shi wrote:

>
> Sorry for chiming in late. This looks problematic IIUC. The patch 5/5
> moved arch_validate_flags() before call_mmap() as the commit log said.
> But shmem_file() does this check:
> mapping->a_ops == &shmem_aops
>
> But mapping->a_ops is not initialized until shmem_mmap(), which is
> called by call_mmap().
>
> So shmem_file() should always return false here. Did I miss something?

Well firstly this is tested and works so you did miss something :)

Bu shmem_mmap() is not setting mapping->a_ops, it's setting vma->vm_ops.

__shmem_get_inode() and shmem_symlink() set mapping->a_ops.