[dm-devel] [dm:for-next 20/20] drivers/md/dm.c:850:43: warning: variable 'bio' is uninitialized when used here

[Damien Le Moal]

On 2021/06/03 6:26, kernel test robot wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git for-next
> head:   2c243153d1d4be4e23735cd10984ac17c7a54531
> commit: 2c243153d1d4be4e23735cd10984ac17c7a54531 [20/20] dm: Forbid requeue of writes to zones
> config: riscv-randconfig-r011-20210602 (attached as .config)
> compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project d41cb6bb2607fa5c7a9df2b3dab361353657d225)
> reproduce (this is a W=1 build):
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         # install riscv cross compiling tool for clang build
>         # apt-get install binutils-riscv64-linux-gnu
>         # https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git/commit/?id=2c243153d1d4be4e23735cd10984ac17c7a54531
>         git remote add dm https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git
>         git fetch --no-tags dm for-next
>         git checkout 2c243153d1d4be4e23735cd10984ac17c7a54531
>         # save the attached .config to linux build tree
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=riscv 
> 
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp at intel.com>
> 
> All warnings (new ones prefixed by >>):
> 
>>> drivers/md/dm.c:850:43: warning: variable 'bio' is uninitialized when used here [-Wuninitialized]
>                                !WARN_ON_ONCE(dm_is_zone_write(md, bio)))
>                                                                   ^~~
>    include/asm-generic/bug.h:102:25: note: expanded from macro 'WARN_ON_ONCE'
>            int __ret_warn_on = !!(condition);                      \
>                                   ^~~~~~~~~
>    drivers/md/dm.c:832:17: note: initialize the variable 'bio' to silence this warning
>            struct bio *bio;
>                           ^
>                            = NULL
>    1 warning generated.
> 
> 
> vim +/bio +850 drivers/md/dm.c
> 
>    823	
>    824	/*
>    825	 * Decrements the number of outstanding ios that a bio has been
>    826	 * cloned into, completing the original io if necc.
>    827	 */
>    828	static void dec_pending(struct dm_io *io, blk_status_t error)
>    829	{
>    830		unsigned long flags;
>    831		blk_status_t io_error;
>    832		struct bio *bio;
>    833		struct mapped_device *md = io->md;
>    834	
>    835		/* Push-back supersedes any I/O errors */
>    836		if (unlikely(error)) {
>    837			spin_lock_irqsave(&io->endio_lock, flags);
>    838			if (!(io->status == BLK_STS_DM_REQUEUE && __noflush_suspending(md)))
>    839				io->status = error;
>    840			spin_unlock_irqrestore(&io->endio_lock, flags);
>    841		}
>    842	
>    843		if (atomic_dec_and_test(&io->io_count)) {
>    844			if (io->status == BLK_STS_DM_REQUEUE) {
>    845				/*
>    846				 * Target requested pushing back the I/O.
>    847				 */
>    848				spin_lock_irqsave(&md->deferred_lock, flags);
>    849				if (__noflush_suspending(md) &&
>  > 850				    !WARN_ON_ONCE(dm_is_zone_write(md, bio)))

Mike,

This needs to be WARN_ON_ONCE(dm_is_zone_write(md, io->orig_bio)).
Or better, we can move line 863 below right after the
"if (atomic_dec_and_test(&io->io_count)) {" above.

Do you want me to resend ? Or can you fix it up ?

Thanks !


>    851					/* NOTE early return due to BLK_STS_DM_REQUEUE below */
>    852					bio_list_add_head(&md->deferred, io->orig_bio);
>    853				else
>    854					/*
>    855					 * noflush suspend was interrupted or this is
>    856					 * a write to a zoned target.
>    857					 */
>    858					io->status = BLK_STS_IOERR;
>    859				spin_unlock_irqrestore(&md->deferred_lock, flags);
>    860			}
>    861	
>    862			io_error = io->status;
>    863			bio = io->orig_bio;
>    864			end_io_acct(io);
>    865			free_io(md, io);
>    866	
>    867			if (io_error == BLK_STS_DM_REQUEUE)
>    868				return;
>    869	
>    870			if ((bio->bi_opf & REQ_PREFLUSH) && bio->bi_iter.bi_size) {
>    871				/*
>    872				 * Preflush done for flush with data, reissue
>    873				 * without REQ_PREFLUSH.
>    874				 */
>    875				bio->bi_opf &= ~REQ_PREFLUSH;
>    876				queue_io(md, bio);
>    877			} else {
>    878				/* done with normal IO or empty flush */
>    879				if (io_error)
>    880					bio->bi_status = io_error;
>    881				bio_endio(bio);
>    882			}
>    883		}
>    884	}
>    885	
> 
> ---
> 0-DAY CI Kernel Test Service, Intel Corporation
> https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
> 


-- 
Damien Le Moal
Western Digital Research