Re: [PATCH v10 7/8] PCI/P2PDMA: Allow userspace VMA allocations through sysfs

[Greg Kroah-Hartman]

On Thu, Sep 22, 2022 at 10:39:25AM -0600, Logan Gunthorpe wrote:
> Create a sysfs bin attribute called "allocate" under the existing
> "p2pmem" group. The only allowable operation on this file is the mmap()
> call.
> 
> When mmap() is called on this attribute, the kernel allocates a chunk of
> memory from the genalloc and inserts the pages into the VMA. The
> dev_pagemap .page_free callback will indicate when these pages are no
> longer used and they will be put back into the genalloc.
> 
> On device unbind, remove the sysfs file before the memremap_pages are
> cleaned up. This ensures unmap_mapping_range() is called on the files
> inode and no new mappings can be created.
> 
> Signed-off-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
> ---
>  drivers/pci/p2pdma.c | 124 +++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 124 insertions(+)

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