Messages in this thread Patch in this message | | | From | Arnd Bergmann <> | Subject | [PATCH] nvdimm: avoid bogus -Wmaybe-uninitialized warning | Date | Tue, 1 Aug 2017 13:48:48 +0200 |
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Removing the btt_rw_page/pmem_rw_page functions had 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.
Fixes: 503a5e89b1de ("drivers/nvdimm/btt.c: remove btt_rw_page()") Fixes: 58100d6e735e ("drivers/nvdimm/pmem.c: remove pmem_rw_page()") Signed-off-by: Arnd Bergmann <arnd@arndb.de> --- drivers/nvdimm/nd.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/nvdimm/nd.h b/drivers/nvdimm/nd.h index e1b5715bd91f..64f79a156456 100644 --- a/drivers/nvdimm/nd.h +++ b/drivers/nvdimm/nd.h @@ -392,8 +392,10 @@ static inline bool nd_iostat_start(struct bio *bio, unsigned long *start) { 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), -- 2.9.0
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