kernel: vmcoreinfo: allocate vmcoreinfo_data based on VMCOREINFO_BYTES

kernel: vmcoreinfo: allocate vmcoreinfo_data based on VMCOREINFO_BYTES

Patch series "vmcoreinfo: support VMCOREINFO_BYTES larger than PAGE_SIZE".

VMCOREINFO_BYTES is defined as a configurable size, but multiple
code paths implicitly assume it always fits into a single page.

This series removes that assumption by allocating and mapping
vmcoreinfo based on its actual size.

Patch 1 updates vmcoreinfo allocation to use get_order(VMCOREINFO_BYTES).
Patch 2 updates crash kernel handling to correctly allocate and map
multiple pages when copying vmcoreinfo.

This makes vmcoreinfo size consistent across the kernel and avoids
future breakage if VMCOREINFO_BYTES grows.

(No functional change when VMCOREINFO_BYTES == PAGE_SIZE.)

This patch (of 2):

VMCOREINFO_BYTES defines the size of vmcoreinfo data, but the current
implementation assumes a single page allocation.

Allocate vmcoreinfo_data using get_order(VMCOREINFO_BYTES) so that
vmcoreinfo can safely grow beyond PAGE_SIZE.

This avoids hidden assumptions and keeps vmcoreinfo size consistent across
the kernel.

Link: https://lkml.kernel.org/r/20251216132801.807260-1-pnina.feder@mobileye.com
Link: https://lkml.kernel.org/r/20251216132801.807260-2-pnina.feder@mobileye.com
Signed-off-by: Pnina Feder <pnina.feder@mobileye.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>