lkml.org 
[lkml]   [2018]   [Mar]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 4.15 058/146] dm bufio: avoid false-positive Wmaybe-uninitialized warning
Date
4.15-stable review patch.  If anyone has any objections, please let me know.

------------------

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/md/dm-bufio.c | 16 ++++++----------
1 file changed, 6 insertions(+), 10 deletions(-)

--- a/drivers/md/dm-bufio.c
+++ b/drivers/md/dm-bufio.c
@@ -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
* 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 ptr;
+ return __vmalloc(c->block_size, gfp_mask, PAGE_KERNEL);
}

/*

\
 
 \ /
  Last update: 2018-03-13 17:57    [W:0.349 / U:24.808 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site