From: Arnd Bergmann arnd@arndb.de

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: Arnd Bergmann arnd@arndb.de [snitzer: moved declarations inside conditional, altered vmalloc return] Signed-off-by: Mike Snitzer snitzer@redhat.com [nc: Backport to 4.9, adjust context for lack of 19809c2da28a] Signed-off-by: Nathan Chancellor natechancellor@gmail.com ---

Hi Greg,

Resending this with a proper prefix and message, in case the other one fell through the cracks. I came across this warning when building with Google's stock GCC 4.9 toolchain on the OnePlus 6. Context was adjusted around lack of commit 19809c2da28a ("mm, vmalloc: use __GFP_HIGHMEM implicitly") in 4.9. Please apply when you get a chance.

Thanks! Nathan

drivers/md/dm-bufio.c | 17 +++++++---------- 1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c index 3ec647e8b9c6..35fd57fdeba9 100644 --- a/drivers/md/dm-bufio.c +++ b/drivers/md/dm-bufio.c @@ -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); @@ -399,16 +396,16 @@ 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 ptr; + return __vmalloc(c->block_size, gfp_mask | __GFP_HIGHMEM, PAGE_KERNEL); }

/*