The patch titled
Subject: nvdimm: avoid bogus -Wmaybe-uninitialized warning
has been added to the -mm tree. Its filename is
nvdimm-avoid-bogus-wmaybe-uninitialized-warning.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/nvdimm-avoid-bogus-wmaybe-uninitialized-warning.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/nvdimm-avoid-bogus-wmaybe-uninitialized-warning.patch
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------------------------------------------------------
From: Arnd Bergmann <arnd@xxxxxxxx>
Subject: nvdimm: avoid bogus -Wmaybe-uninitialized warning
Removing the btt_rw_page/pmem_rw_page functions has a surprising
side-effect of introducing a false-positive warning in another function,
due to changed inlining decisions in gcc:
In file included from drivers/nvdimm/pmem.c:36:0:
drivers/nvdimm/pmem.c: In function 'pmem_make_request':
drivers/nvdimm/nd.h:407:2: error: 'start' may be used uninitialized in this function [-Werror=maybe-uninitialized]
drivers/nvdimm/pmem.c:174:16: note: 'start' was declared here
In file included from drivers/nvdimm/btt.c:27:0:
drivers/nvdimm/btt.c: In function 'btt_make_request':
drivers/nvdimm/nd.h:407:2: error: 'start' may be used uninitialized in this function [-Werror=maybe-uninitialized]
drivers/nvdimm/btt.c:1202:16: note: 'start' was declared here
The problem is that gcc fails to track the value of the 'do_acct' variable
here and has to read it back from stack, but it does remember that 'start'
may be uninitialized sometimes.
This shuts up the warning by making nd_iostat_start() always initialize
the 'start' variable. In those cases that gcc successfully tracks the
state of the variable, this will have no effect.
Link: http://lkml.kernel.org/r/20170801114926.1171418-1-arnd@xxxxxxxx
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Vishal Verma <vishal.l.verma@xxxxxxxxx>
Cc: Toshi Kani <toshi.kani@xxxxxxx>
Cc: Johannes Thumshirn <jthumshirn@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/nvdimm/nd.h | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff -puN drivers/nvdimm/nd.h~nvdimm-avoid-bogus-wmaybe-uninitialized-warning drivers/nvdimm/nd.h
--- a/drivers/nvdimm/nd.h~nvdimm-avoid-bogus-wmaybe-uninitialized-warning
+++ a/drivers/nvdimm/nd.h
@@ -392,8 +392,10 @@ static inline bool nd_iostat_start(struc
{
struct gendisk *disk = bio->bi_bdev->bd_disk;
- if (!blk_queue_io_stat(disk->queue))
+ if (!blk_queue_io_stat(disk->queue)) {
+ *start = 0;
return false;
+ }
*start = jiffies;
generic_start_io_acct(bio_data_dir(bio),
_
Patches currently in -mm which might be from arnd@xxxxxxxx are
kasan-avoid-wmaybe-uninitialized-warning-v3.patch
adfs-use-unsigned-types-for-memcpy-length.patch
nvdimm-avoid-bogus-wmaybe-uninitialized-warning.patch
fscache-fix-fscache_objlist_show-format-processing.patch
ib-mlx4-fix-sprintf-format-warning.patch
iopoll-avoid-wint-in-bool-context-warning.patch
kbuild-use-fshort-wchar-globally.patch
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