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Commit e1fba17e authored by Arnd Bergmann's avatar Arnd Bergmann Committed by Greg Kroah-Hartman
Browse files

dm bufio: avoid false-positive Wmaybe-uninitialized warning 

commit 590347e4000356f55eb10b03ced2686bd74dab40 upstream.

gcc-6.3 and earlier show a new warning after a seemingly unrelated
change to the arm64 PAGE_KERNEL definition:

In file included from drivers/md/dm-bufio.c:14:0:
drivers/md/dm-bufio.c: In function 'alloc_buffer':
include/linux/sched/mm.h:182:56: warning: 'noio_flag' may be used uninitialized in this function [-Wmaybe-uninitialized]
  current->flags = (current->flags & ~PF_MEMALLOC_NOIO) | flags;
                                                        ^

The same warning happened earlier on linux-3.18 for MIPS and I did a
workaround for that, but now it's come back.

gcc-7 and newer are apparently smart enough to figure this out, and
other architectures don't show it, so the best I could come up with is
to rework the caller slightly in a way that makes it obvious enough to
all arm64 compilers what is happening here.

Fixes: 41acec624087 ("arm64: kpti: Make use of nG dependent on arm64_kernel_unmapped_at_el0()")
Link: https://patchwork.kernel.org/patch/9692829/


Cc: stable@vger.kernel.org
Signed-off-by: default avatarArnd Bergmann <arnd@arndb.de>
[snitzer: moved declarations inside conditional, altered vmalloc return]
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
[nc: Backport to 4.9, adjust context for lack of 19809c2da28a]
Signed-off-by: default avatarNathan Chancellor <natechancellor@gmail.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 02136f32

drivers/md/dm-bufio.c

+7 −10
Original line number Diff line number Diff line
@@ -373,9 +373,6 @@ static void __cache_size_refresh(void) 
static void *alloc_buffer_data(struct dm_bufio_client *c, gfp_t gfp_mask,

			       enum data_mode *data_mode)

{

	unsigned noio_flag;

	void *ptr;



	if (c->block_size <= DM_BUFIO_BLOCK_SIZE_SLAB_LIMIT) {

		*data_mode = DATA_MODE_SLAB;

		return kmem_cache_alloc(DM_BUFIO_CACHE(c), gfp_mask);
@@ -399,18 +396,18 @@ static void *alloc_buffer_data(struct dm_bufio_client *c, gfp_t gfp_mask, 
	 * all allocations done by this process (including pagetables) are done

	 * as if GFP_NOIO was specified.

	 */

	if (gfp_mask & __GFP_NORETRY) {

		unsigned noio_flag = memalloc_noio_save();

		void *ptr = __vmalloc(c->block_size, gfp_mask | __GFP_HIGHMEM,

				      PAGE_KERNEL);



	if (gfp_mask & __GFP_NORETRY)

		noio_flag = memalloc_noio_save();



	ptr = __vmalloc(c->block_size, gfp_mask | __GFP_HIGHMEM, PAGE_KERNEL);



	if (gfp_mask & __GFP_NORETRY)

		memalloc_noio_restore(noio_flag);



		return ptr;

	}



	return __vmalloc(c->block_size, gfp_mask | __GFP_HIGHMEM, PAGE_KERNEL);

}



/*

 * Free buffer's data.

 */