mm/vma: minor cleanup of expand_[upwards, downwards]()

Adjust the stack expansion functions expand_upwards() and
expand_downwards() such that they are expressed in terms of named constant
values, and make use of vma_start_pgoff().

This clearly documents that we are referencing the page offset of the start
of the VMA.

Additionally this cleans up the overflow check in expand_upwards().

No functional change intended.

Link: https://lore.kernel.org/20260710-b4-pre-scalable-cow-v2-16-2a5aa403d977@kernel.org
Signed-off-by: Lorenzo Stoakes <ljs@kernel.org>
Reviewed-by: Pedro Falcato <pfalcato@suse.de>
Reviewed-by: Gregory Price <gourry@gourry.net>
Reviewed-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
Cc: Ackerley Tng <ackerleytng@google.com>
Cc: David Hildenbrand (Arm) <david@kernel.org>
Cc: Kai Huang <kai.huang@intel.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: SJ Park <sj@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Liam R. Howlett (Oracle) <liam@infradead.org>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

0 files changed, 0 insertions, 0 deletions