Re: [PATCH v5 09/38] drivers/usb/mon: update to use mmap_prepare + map kernel pages

Replace the deprecated .mmap hook with its replacement .mmap_prepare. As
part of this change, additionally take the approach of mapping pages upon
mmap rather than providing a fault handler.

The page span cannot be mutated when an mmap mapping is in place, so this
is safe to do in advance (the MON_IOCT_RING_SIZE ioctl operation exits
-EBUSY if it's attempted, gated by the rp->mmap_active reference count).

Utilise the newly introduced mmap_action_map_discontig_kernel_pages() to do
this, which allows for iteration over pages in mon_bin_discontig_get().

mon_bin_discontig_init() increments the rp->mmap_active reference count to
stabilise page spans. Should an error arise the core unmaps the VMA and
mon_bin_vma_close() drops the reference again.

[ ... ]
access raises SIGBUS, as with other pre-populated kernel mappings.

Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261009-b4-mmap-prepare-vma-flag-sanify-v5-0-923b70125b1e@kernel.org?part=9