Re: [PATCH v2 1/4] kernfs: remove page_mkwrite() from vm_operations_struct

[Greg Kroah-Hartman]

On Tue, Jun 11, 2024 at 12:27:29PM -0600, Martin Oliveira wrote:
> The .page_mkwrite operator of kernfs just calls file_update_time().
> This is the same behaviour that the fault code does if .page_mkwrite is
> not set.
> 
> Furthermore, having the page_mkwrite() operator causes
> writable_file_mapping_allowed() to fail due to
> vma_needs_dirty_tracking() on the gup flow, which is a pre-requisite for
> enabling P2PDMA over RDMA.
> 
> There are no users of .page_mkwrite and no known valid use cases, so
> just remove the .page_mkwrite from kernfs_ops and return -EINVAL if an
> mmap() implementation sets .page_mkwrite.
> 
> Co-developed-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
> Signed-off-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
> Signed-off-by: Martin Oliveira <martin.oliveira@xxxxxxxxxxxxx>
> ---
>  fs/kernfs/file.c | 26 +++-----------------------
>  1 file changed, 3 insertions(+), 23 deletions(-)

Acked-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>