stackdepot: use gfp_nested_mask() instead of open coded masking

The stackdepot code is used by KASAN and lockdep for recoding stack
traces.  Both of these track allocation context information, and so their
internal allocations must obey the caller allocation contexts to avoid
generating their own false positive warnings that have nothing to do with
the code they are instrumenting/tracking.

We also don't want recording stack traces to deplete emergency memory
reserves - debug code is useless if it creates new issues that can't be
replicated when the debug code is disabled.

Switch the stackdepot allocation masking to use gfp_nested_mask() to
address these issues.  gfp_nested_mask() also strips GFP_ZONEMASK
naturally, so that greatly simplifies this code.

Link: https://lkml.kernel.org/r/20240430054604.4169568-3-david@fromorbit.com
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Marco Elver <elver@google.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

lib/stackdepot.c

@@ -624,15 +624,8 @@ depot_stack_handle_t stack_depot_save_flags(unsigned long *entries,
 	 * we won't be able to do that under the lock.
 	 */
 	if (unlikely(can_alloc && !READ_ONCE(new_pool))) {
-		/*
-		 * Zero out zone modifiers, as we don't have specific zone
-		 * requirements. Keep the flags related to allocation in atomic
-		 * contexts, I/O, nolockdep.
-		 */
-		alloc_flags &= ~GFP_ZONEMASK;
-		alloc_flags &= (GFP_ATOMIC | GFP_KERNEL | __GFP_NOLOCKDEP);
-		alloc_flags |= __GFP_NOWARN;
-		page = alloc_pages(alloc_flags, DEPOT_POOL_ORDER);
+		page = alloc_pages(gfp_nested_mask(alloc_flags),
+				   DEPOT_POOL_ORDER);
 		if (page)
 			prealloc = page_address(page);
 	}