mm: kasan: Skip page unpoisoning only if __GFP_SKIP_KASAN_UNPOISON

Currently post_alloc_hook() skips the kasan unpoisoning if the tags will
be zeroed (__GFP_ZEROTAGS) or __GFP_SKIP_KASAN_UNPOISON is passed. Since
__GFP_ZEROTAGS is now accompanied by __GFP_SKIP_KASAN_UNPOISON, remove
the extra check.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Peter Collingbourne <pcc@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Link: https://lore.kernel.org/r/20220610152141.2148929-4-catalin.marinas@arm.com
Signed-off-by: Will Deacon <will@kernel.org>

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index f6ed240..bf45a6a 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2361,7 +2361,7 @@ static inline bool check_new_pcp(struct page *page, unsigned int order)
 }
 #endif /* CONFIG_DEBUG_VM */
 
-static inline bool should_skip_kasan_unpoison(gfp_t flags, bool init_tags)
+static inline bool should_skip_kasan_unpoison(gfp_t flags)
 {
        /* Don't skip if a software KASAN mode is enabled. */
        if (IS_ENABLED(CONFIG_KASAN_GENERIC) ||
@@ -2373,12 +2373,10 @@ static inline bool should_skip_kasan_unpoison(gfp_t flags, bool init_tags)
                return true;
 
        /*
-        * With hardware tag-based KASAN enabled, skip if either:
-        *
-        * 1. Memory tags have already been cleared via tag_clear_highpage().
-        * 2. Skipping has been requested via __GFP_SKIP_KASAN_UNPOISON.
+        * With hardware tag-based KASAN enabled, skip if this has been
+        * requested via __GFP_SKIP_KASAN_UNPOISON.
         */
-       return init_tags || (flags & __GFP_SKIP_KASAN_UNPOISON);
+       return flags & __GFP_SKIP_KASAN_UNPOISON;
 }
 
 static inline bool should_skip_init(gfp_t flags)
@@ -2430,7 +2428,7 @@ inline void post_alloc_hook(struct page *page, unsigned int order,
                /* Note that memory is already initialized by the loop above. */
                init = false;
        }
-       if (!should_skip_kasan_unpoison(gfp_flags, init_tags)) {
+       if (!should_skip_kasan_unpoison(gfp_flags)) {
                /* Unpoison shadow memory or set memory tags. */
                kasan_unpoison_pages(page, order, init);