Commit 590347e4 authored Feb 22, 2018 by Arnd Bergmann Committed by Mike Snitzer Mar 06, 2018

dm bufio: avoid false-positive Wmaybe-uninitialized warning

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: 41acec62 ("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: Arnd Bergmann <arnd@arndb.de>
[snitzer: moved declarations inside conditional, altered vmalloc return]
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

parent 661e50bc

drivers/md/dm-bufio.c

+6 −10

Original line number	Diff line number	Diff line
		@@ -386,9 +386,6 @@ 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);
		@@ -412,18 +409,17 @@ 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, PAGE_KERNEL);

		if (gfp_mask & __GFP_NORETRY)
		noio_flag = memalloc_noio_save();

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

		if (gfp_mask & __GFP_NORETRY)
		memalloc_noio_restore(noio_flag);

		return ptr;
		}

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

		/*
		* Free buffer's data.
		*/

Admin message