mm/khugepaged: fix vm_lock/i_mmap_rwsem inversion in retract_page_tables

mm/khugepaged: fix vm_lock/i_mmap_rwsem inversion in retract_page_tables

Internal syscaller on linux-next reported a lock inversion cause by
vm_lock being taken after i_mmap_rwsem:

======================================================
WARNING: possible circular locking dependency detected
6.2.0-next-20230301-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor115/5084 is trying to acquire lock:
ffff888078307a90 (&vma->vm_lock->lock){++++}-{3:3}, at: vma_start_write include/linux/mm.h:678 [inline]
ffff888078307a90 (&vma->vm_lock->lock){++++}-{3:3}, at: retract_page_tables mm/khugepaged.c:1826 [inline]
ffff888078307a90 (&vma->vm_lock->lock){++++}-{3:3}, at: collapse_file+0x4fa5/0x5980 mm/khugepaged.c:2204

but task is already holding lock:
ffff88801f93efa8 (&mapping->i_mmap_rwsem){++++}-{3:3}, at: i_mmap_lock_write include/linux/fs.h:468 [inline]
ffff88801f93efa8 (&mapping->i_mmap_rwsem){++++}-{3:3}, at: retract_page_tables mm/khugepaged.c:1745 [inline]
ffff88801f93efa8 (&mapping->i_mmap_rwsem){++++}-{3:3}, at: collapse_file+0x3da6/0x5980 mm/khugepaged.c:2204

retract_page_tables takes i_mmap_rwsem before exclusive mmap_lock, which
is inverse to normal order.  Deadlock is avoided by try-locking mmap_lock
and skipping on failure to obtain it.  Locking the VMA should use the same
locking pattern to avoid this lock inversion.

Link: https://lkml.kernel.org/r/20230303213250.3555716-1-surenb@google.com
Fixes: 44a83f2083bd ("mm/khugepaged: write-lock VMA while collapsing a huge page")
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reported-by: <syzbot+8955a9646d1a48b8be92@syzkaller.appspotmail.com>
Cc: Arjun Roy <arjunroy@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Greg Thelen <gthelen@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: kernel-team@android.com
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Michel Lespinasse <michel@lespinasse.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Peter Oskolkov <posk@google.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Punit Agrawal <punit.agrawal@bytedance.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Song Liu <songliubraving@fb.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>