On Thu, Jun 07, 2018 at 10:03:44PM -0700, Nathan Chancellor wrote:
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
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);
} /* -- 2.17.1
Gah, sorry, forgot to add a prefix. This should only be applied to 4.9, it's already present in 4.14 and it isn't needed for 4.4.
Cheers! Nathan