remap_file_pages: correctly handle the case of a NULL vm_ops pointer
remap_file_pages: correctly handle the case of a NULL vm_ops pointer

In commit 0b173bc4daa8 ("mm: kill vma flag VM_CAN_NONLINEAR") we
replaced the VM_CAN_NONLINEAR test with checking whether the mapping has
a '->remap_pages()' vm operation, but there is no guarantee that there
it even has a vm_ops pointer at all.

Add the appropriate test for NULL vm_ops.

Reported-by: Sasha Levin <611d453c03d02ce713e72b62ff6a901ea7e9cd77@gmail.com>
Cc: Konstantin Khlebnikov <3b96b99f19643d33e1bfa1caa535c041c3608549@openvz.org>
Cc: Andrew Morton <5c1e68b099950c134891f0b6e179498a8ebe9cf9@linux-foundation.org>
Signed-off-by: Linus Torvalds <69652caca27c8b940640ad396ab71f93cacec34f@linux-foundation.org>

KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs