mm, madvise: use standard madvise locking in madvise_set_anon_name()

mm, madvise: use standard madvise locking in madvise_set_anon_name()

Use madvise_lock()/madvise_unlock() in madvise_set_anon_name() in the same
way as in do_madvise().  This narrows the lock scope a bit and reuses
existing functionality.  get_lock_mode() already picks the correct
MADVISE_MMAP_WRITE_LOCK mode for __MADV_SET_ANON_VMA_NAME so we can just
remove the explicit assignment.

There is a user visible change in that the prctl(PR_SET_VMA,
PR_SET_VMA_ANON_NAME...) might now return -EINTR.

Link: https://lkml.kernel.org/r/20250624-anon_name_cleanup-v2-4-600075462a11@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Tested-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Colin Cross <ccross@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>