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dm bufio: avoid false-positive Wmaybe-uninitialized warning

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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: 41acec6240 ("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>
This commit is contained in:
Arnd Bergmann 2018-02-22 16:56:16 +01:00 committed by Mike Snitzer
parent 661e50bc85
commit 590347e400
1 changed files with 6 additions and 10 deletions
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16
drivers/md/dm-bufio.c
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@ -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);
@ -412,16 +409,15 @@ 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);
}
/*