mm, page_alloc: put should_fail_alloc_page() back behing CONFIG_FAIL_PAGE_ALLOC

This mostly reverts commit af3b854 ("mm/page_alloc.c: allow error
injection").  The commit made should_fail_alloc_page() a noinline function
that's always called from the page allocation hotpath, even if it's empty
because CONFIG_FAIL_PAGE_ALLOC is not enabled, and there is no option to
disable it and prevent the associated function call overhead.

As with the preceding patch "mm, slab: put should_failslab back behind
CONFIG_SHOULD_FAILSLAB" and for the same reasons, put the
should_fail_alloc_page() back behind the config option.  When enabled, the
ALLOW_ERROR_INJECTION and BTF_ID records are preserved so it's not a
complete revert.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Vlastimil Babka <[email protected]>
Cc: Akinobu Mita <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Andrii Nakryiko <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: Daniel Borkmann <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Eduard Zingerman <[email protected]>
Cc: Hao Luo <[email protected]>
Cc: Hyeonggon Yoo <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: John Fastabend <[email protected]>
Cc: KP Singh <[email protected]>
Cc: Martin KaFai Lau <[email protected]>
Cc: Mateusz Guzik <[email protected]>
Cc: Roman Gushchin <[email protected]>
Cc: Song Liu <[email protected]>
Cc: Stanislav Fomichev <[email protected]>
Cc: Yonghong Song <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: tehcaster

include/linux/fault-inject.h

@@ -91,12 +91,10 @@ static inline void fault_config_init(struct fault_config *config,
 
 struct kmem_cache;
 
-bool should_fail_alloc_page(gfp_t gfp_mask, unsigned int order);
-
 #ifdef CONFIG_FAIL_PAGE_ALLOC
-bool __should_fail_alloc_page(gfp_t gfp_mask, unsigned int order);
+bool should_fail_alloc_page(gfp_t gfp_mask, unsigned int order);
 #else
-static inline bool __should_fail_alloc_page(gfp_t gfp_mask, unsigned int order)
+static inline bool should_fail_alloc_page(gfp_t gfp_mask, unsigned int order)
 {
 	return false;
 }

kernel/bpf/verifier.c

@@ -21122,7 +21122,9 @@ BTF_SET_START(btf_non_sleepable_error_inject)
  * Assume non-sleepable from bpf safety point of view.
  */
 BTF_ID(func, __filemap_add_folio)
+#ifdef CONFIG_FAIL_PAGE_ALLOC
 BTF_ID(func, should_fail_alloc_page)
+#endif
 #ifdef CONFIG_FAILSLAB
 BTF_ID(func, should_failslab)
 #endif

mm/fail_page_alloc.c

@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <linux/fault-inject.h>
+#include <linux/error-injection.h>
 #include <linux/mm.h>
 
 static struct {
@@ -21,7 +22,7 @@ static int __init setup_fail_page_alloc(char *str)
 }
 __setup("fail_page_alloc=", setup_fail_page_alloc);
 
-bool __should_fail_alloc_page(gfp_t gfp_mask, unsigned int order)
+bool should_fail_alloc_page(gfp_t gfp_mask, unsigned int order)
 {
 	int flags = 0;
 
@@ -41,6 +42,7 @@ bool __should_fail_alloc_page(gfp_t gfp_mask, unsigned int order)
 
 	return should_fail_ex(&fail_page_alloc.attr, 1 << order, flags);
 }
+ALLOW_ERROR_INJECTION(should_fail_alloc_page, TRUE);
 
 #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
 

mm/page_alloc.c

@@ -3050,12 +3050,6 @@ struct page *rmqueue(struct zone *preferred_zone,
 	return page;
 }
 
-noinline bool should_fail_alloc_page(gfp_t gfp_mask, unsigned int order)
-{
-	return __should_fail_alloc_page(gfp_mask, order);
-}
-ALLOW_ERROR_INJECTION(should_fail_alloc_page, TRUE);
-
 static inline long __zone_watermark_unusable_free(struct zone *z,
 				unsigned int order, unsigned int alloc_flags)
 {