mm/vmalloc: use batched page requests in bulk-allocator

In case of simultaneous vmalloc allocations, for example it is 1GB and 12
CPUs my system is able to hit "BUG: soft lockup" for !CONFIG_PREEMPT
kernel.

  RIP: 0010:__alloc_pages_bulk+0xa9f/0xbb0
  Call Trace:
   __vmalloc_node_range+0x11c/0x2d0
   __vmalloc_node+0x4b/0x70
   fix_size_alloc_test+0x44/0x60 [test_vmalloc]
   test_func+0xe7/0x1f0 [test_vmalloc]
   kthread+0x11a/0x140
   ret_from_fork+0x22/0x30

To address this issue invoke a bulk-allocator many times until all pages
are obtained, i.e.  do batched page requests adding cond_resched()
meanwhile to reschedule.  Batched value is hard-coded and is 100 pages per
call.

Link: https://lkml.kernel.org/r/20210707182639.31282-1-urezki@gmail.com
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Oleksiy Avramchenko <oleksiy.avramchenko@sonymobile.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>