drm/amdkfd: Don't call mmput from MMU notifier callback

In the Linux kernel, the following vulnerability has been resolved:

drm/amdkfd: Don't call mmput from MMU notifier callback

If the process is exiting, the mmput inside mmu notifier callback from

compactd or fork or numa balancing could release the last reference

of mm struct to call exit_mmap and free_pgtable, this triggers deadlock

with below backtrace.

The deadlock will leak kfd process as mmu notifier release is not called

and cause VRAM leaking.

The fix is to take mm reference mmget_non_zero when adding prange to the

deferred list to pair with mmput in deferred list work.

If prange split and add into pchild list, the pchild work_item.mm is not

used, so remove the mm parameter from svm_range_unmap_split and

svm_range_add_child.

The backtrace of hung task:

INFO: task python:348105 blocked for more than 64512 seconds.

Call Trace:

__schedule+0x1c3/0x550

schedule+0x46/0xb0

rwsem_down_write_slowpath+0x24b/0x4c0

unlink_anon_vmas+0xb1/0x1c0

free_pgtables+0xa9/0x130

exit_mmap+0xbc/0x1a0

mmput+0x5a/0x140

svm_range_cpu_invalidate_pagetables+0x2b/0x40 [amdgpu]

mn_itree_invalidate+0x72/0xc0

__mmu_notifier_invalidate_range_start+0x48/0x60

try_to_unmap_one+0x10fa/0x1400

rmap_walk_anon+0x196/0x460

try_to_unmap+0xbb/0x210

migrate_page_unmap+0x54d/0x7e0

migrate_pages_batch+0x1c3/0xae0

migrate_pages_sync+0x98/0x240

migrate_pages+0x25c/0x520

compact_zone+0x29d/0x590

compact_zone_order+0xb6/0xf0

try_to_compact_pages+0xbe/0x220

__alloc_pages_direct_compact+0x96/0x1a0

__alloc_pages_slowpath+0x410/0x930

__alloc_pages_nodemask+0x3a9/0x3e0

do_huge_pmd_anonymous_page+0xd7/0x3e0

__handle_mm_fault+0x5e3/0x5f0

handle_mm_fault+0xf7/0x2e0

hmm_vma_fault.isra.0+0x4d/0xa0

walk_pmd_range.isra.0+0xa8/0x310

walk_pud_range+0x167/0x240

walk_pgd_range+0x55/0x100

__walk_page_range+0x87/0x90

walk_page_range+0xf6/0x160

hmm_range_fault+0x4f/0x90

amdgpu_hmm_range_get_pages+0x123/0x230 [amdgpu]

amdgpu_ttm_tt_get_user_pages+0xb1/0x150 [amdgpu]

init_user_pages+0xb1/0x2a0 [amdgpu]

amdgpu_amdkfd_gpuvm_alloc_memory_of_gpu+0x543/0x7d0 [amdgpu]

kfd_ioctl_alloc_memory_of_gpu+0x24c/0x4e0 [amdgpu]

kfd_ioctl+0x29d/0x500 [amdgpu]

(cherry picked from commit a29e067bd38946f752b0ef855f3dfff87e77bec7)