mm/page_alloc: remove obsolete gfpflags_normal_context()

Since commit dacb5d88 ("tcp: fix page frag corruption on page fault"),
there's no caller of gfpflags_normal_context().  Remove it as this helper
is strictly tied to the sk page frag usage and there won't be other user
in the future.

[linmiaohe@huawei.com: fix htmldocs]
  Link: https://lkml.kernel.org/r/1bc55727-9b66-0e9e-c306-f10c4716ea89@huawei.com
Link: https://lkml.kernel.org/r/20220916072257.9639-16-linmiaohe@huawei.comSigned-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Documentation/core-api/mm-api.rst

@@ -19,9 +19,6 @@ User Space Memory Access
 Memory Allocation Controls
 ==========================
 
-.. kernel-doc:: include/linux/gfp.h
-   :internal:
-
 .. kernel-doc:: include/linux/gfp_types.h
    :doc: Page mobility and placement hints
 

include/linux/gfp.h

@@ -36,29 +36,6 @@ static inline bool gfpflags_allow_blocking(const gfp_t gfp_flags)
 	return !!(gfp_flags & __GFP_DIRECT_RECLAIM);
 }
 
-/**
- * gfpflags_normal_context - is gfp_flags a normal sleepable context?
- * @gfp_flags: gfp_flags to test
- *
- * Test whether @gfp_flags indicates that the allocation is from the
- * %current context and allowed to sleep.
- *
- * An allocation being allowed to block doesn't mean it owns the %current
- * context.  When direct reclaim path tries to allocate memory, the
- * allocation context is nested inside whatever %current was doing at the
- * time of the original allocation.  The nested allocation may be allowed
- * to block but modifying anything %current owns can corrupt the outer
- * context's expectations.
- *
- * %true result from this function indicates that the allocation context
- * can sleep and use anything that's associated with %current.
- */
-static inline bool gfpflags_normal_context(const gfp_t gfp_flags)
-{
-	return (gfp_flags & (__GFP_DIRECT_RECLAIM | __GFP_MEMALLOC)) ==
-		__GFP_DIRECT_RECLAIM;
-}
-
 #ifdef CONFIG_HIGHMEM
 #define OPT_ZONE_HIGHMEM ZONE_HIGHMEM
 #else