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* drivers/md/dm-writecache.c:1554 writecache_map() warn: inconsistent returns '&wc->lock'.
@ 2022-08-05  9:08 Dan Carpenter
  2022-08-08 14:50 ` [PATCH] dm-writecache: drop the lock on an 'impossible' path Mikulas Patocka
  0 siblings, 1 reply; 2+ messages in thread
From: Dan Carpenter @ 2022-08-05  9:08 UTC (permalink / raw)
  To: kbuild, Mikulas Patocka; +Cc: lkp, kbuild-all, linux-kernel, Mike Snitzer

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   b44f2fd87919b5ae6e1756d4c7ba2cbba22238e1
commit: df699cc16ea5ef93a917676dcdd4376e02860ad5 dm writecache: report invalid return from writecache_map helpers
config: arc-randconfig-m041-20220804 (https://download.01.org/0day-ci/archive/20220805/202208050301.roHRxc6O-lkp@intel.com/config)
compiler: arc-elf-gcc (GCC) 12.1.0

If you fix the issue, kindly add following tag where applicable
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>

smatch warnings:
drivers/md/dm-writecache.c:1554 writecache_map() warn: inconsistent returns '&wc->lock'.

vim +1554 drivers/md/dm-writecache.c

cdd4d7832d51e0 Mike Snitzer    2021-07-12  1484  static int writecache_map(struct dm_target *ti, struct bio *bio)
cdd4d7832d51e0 Mike Snitzer    2021-07-12  1485  {
cdd4d7832d51e0 Mike Snitzer    2021-07-12  1486  	struct dm_writecache *wc = ti->private;
15cb6f39dbaf39 Mike Snitzer    2021-07-12  1487  	enum wc_map_op map_op;
cdd4d7832d51e0 Mike Snitzer    2021-07-12  1488  
cdd4d7832d51e0 Mike Snitzer    2021-07-12  1489  	bio->bi_private = NULL;
cdd4d7832d51e0 Mike Snitzer    2021-07-12  1490  
cdd4d7832d51e0 Mike Snitzer    2021-07-12  1491  	wc_lock(wc);
cdd4d7832d51e0 Mike Snitzer    2021-07-12  1492  
cdd4d7832d51e0 Mike Snitzer    2021-07-12  1493  	if (unlikely(bio->bi_opf & REQ_PREFLUSH)) {
15cb6f39dbaf39 Mike Snitzer    2021-07-12  1494  		map_op = writecache_map_flush(wc, bio);
15cb6f39dbaf39 Mike Snitzer    2021-07-12  1495  		goto done;
dcd195071f22d4 Mikulas Patocka 2020-01-15  1496  	}
dcd195071f22d4 Mikulas Patocka 2020-01-15  1497  
cdd4d7832d51e0 Mike Snitzer    2021-07-12  1498  	bio->bi_iter.bi_sector = dm_target_offset(ti, bio->bi_iter.bi_sector);
dcd195071f22d4 Mikulas Patocka 2020-01-15  1499  
cdd4d7832d51e0 Mike Snitzer    2021-07-12  1500  	if (unlikely((((unsigned)bio->bi_iter.bi_sector | bio_sectors(bio)) &
cdd4d7832d51e0 Mike Snitzer    2021-07-12  1501  				(wc->block_size / 512 - 1)) != 0)) {
cdd4d7832d51e0 Mike Snitzer    2021-07-12  1502  		DMERR("I/O is not aligned, sector %llu, size %u, block size %u",
cdd4d7832d51e0 Mike Snitzer    2021-07-12  1503  		      (unsigned long long)bio->bi_iter.bi_sector,
cdd4d7832d51e0 Mike Snitzer    2021-07-12  1504  		      bio->bi_iter.bi_size, wc->block_size);
15cb6f39dbaf39 Mike Snitzer    2021-07-12  1505  		map_op = WC_MAP_ERROR;
15cb6f39dbaf39 Mike Snitzer    2021-07-12  1506  		goto done;
cdd4d7832d51e0 Mike Snitzer    2021-07-12  1507  	}
cdd4d7832d51e0 Mike Snitzer    2021-07-12  1508  
cdd4d7832d51e0 Mike Snitzer    2021-07-12  1509  	if (unlikely(bio_op(bio) == REQ_OP_DISCARD)) {
15cb6f39dbaf39 Mike Snitzer    2021-07-12  1510  		map_op = writecache_map_discard(wc, bio);
15cb6f39dbaf39 Mike Snitzer    2021-07-12  1511  		goto done;
48debafe4f2fea Mikulas Patocka 2018-03-08  1512  	}
48debafe4f2fea Mikulas Patocka 2018-03-08  1513  
cdd4d7832d51e0 Mike Snitzer    2021-07-12  1514  	if (bio_data_dir(bio) == READ)
cdd4d7832d51e0 Mike Snitzer    2021-07-12  1515  		map_op = writecache_map_read(wc, bio);
48debafe4f2fea Mikulas Patocka 2018-03-08  1516  	else
cdd4d7832d51e0 Mike Snitzer    2021-07-12  1517  		map_op = writecache_map_write(wc, bio);
15cb6f39dbaf39 Mike Snitzer    2021-07-12  1518  done:
cdd4d7832d51e0 Mike Snitzer    2021-07-12  1519  	switch (map_op) {
cdd4d7832d51e0 Mike Snitzer    2021-07-12  1520  	case WC_MAP_REMAP_ORIGIN:
5c0de3d72f8c05 Mikulas Patocka 2021-06-28  1521  		if (likely(wc->pause != 0)) {
5c0de3d72f8c05 Mikulas Patocka 2021-06-28  1522  			if (bio_op(bio) == REQ_OP_WRITE) {
95b88f4d71cb95 Mikulas Patocka 2021-06-25  1523  				dm_iot_io_begin(&wc->iot, 1);
95b88f4d71cb95 Mikulas Patocka 2021-06-25  1524  				bio->bi_private = (void *)2;
95b88f4d71cb95 Mikulas Patocka 2021-06-25  1525  			}
5c0de3d72f8c05 Mikulas Patocka 2021-06-28  1526  		}
48debafe4f2fea Mikulas Patocka 2018-03-08  1527  		bio_set_dev(bio, wc->dev->bdev);
48debafe4f2fea Mikulas Patocka 2018-03-08  1528  		wc_unlock(wc);
48debafe4f2fea Mikulas Patocka 2018-03-08  1529  		return DM_MAPIO_REMAPPED;
48debafe4f2fea Mikulas Patocka 2018-03-08  1530  
cdd4d7832d51e0 Mike Snitzer    2021-07-12  1531  	case WC_MAP_REMAP:
48debafe4f2fea Mikulas Patocka 2018-03-08  1532  		/* make sure that writecache_end_io decrements bio_in_progress: */
48debafe4f2fea Mikulas Patocka 2018-03-08  1533  		bio->bi_private = (void *)1;
48debafe4f2fea Mikulas Patocka 2018-03-08  1534  		atomic_inc(&wc->bio_in_progress[bio_data_dir(bio)]);
48debafe4f2fea Mikulas Patocka 2018-03-08  1535  		wc_unlock(wc);
48debafe4f2fea Mikulas Patocka 2018-03-08  1536  		return DM_MAPIO_REMAPPED;
48debafe4f2fea Mikulas Patocka 2018-03-08  1537  
cdd4d7832d51e0 Mike Snitzer    2021-07-12  1538  	case WC_MAP_SUBMIT:
48debafe4f2fea Mikulas Patocka 2018-03-08  1539  		wc_unlock(wc);
48debafe4f2fea Mikulas Patocka 2018-03-08  1540  		bio_endio(bio);
48debafe4f2fea Mikulas Patocka 2018-03-08  1541  		return DM_MAPIO_SUBMITTED;
48debafe4f2fea Mikulas Patocka 2018-03-08  1542  
cdd4d7832d51e0 Mike Snitzer    2021-07-12  1543  	case WC_MAP_RETURN:
48debafe4f2fea Mikulas Patocka 2018-03-08  1544  		wc_unlock(wc);
48debafe4f2fea Mikulas Patocka 2018-03-08  1545  		return DM_MAPIO_SUBMITTED;
48debafe4f2fea Mikulas Patocka 2018-03-08  1546  
cdd4d7832d51e0 Mike Snitzer    2021-07-12  1547  	case WC_MAP_ERROR:
48debafe4f2fea Mikulas Patocka 2018-03-08  1548  		wc_unlock(wc);
48debafe4f2fea Mikulas Patocka 2018-03-08  1549  		bio_io_error(bio);
48debafe4f2fea Mikulas Patocka 2018-03-08  1550  		return DM_MAPIO_SUBMITTED;
df699cc16ea5ef Mikulas Patocka 2021-07-27  1551  
df699cc16ea5ef Mikulas Patocka 2021-07-27  1552  	default:
df699cc16ea5ef Mikulas Patocka 2021-07-27  1553  		BUG();
df699cc16ea5ef Mikulas Patocka 2021-07-27 @1554  		return -1;

This only warning only happens if you CONFIG_ the BUG() away.  Hard to
tell how far we really care about dealing with impossible situations...

48debafe4f2fea Mikulas Patocka 2018-03-08  1555  	}
cdd4d7832d51e0 Mike Snitzer    2021-07-12  1556  }

-- 
0-DAY CI Kernel Test Service
https://01.org/lkp


^ permalink raw reply	[flat|nested] 2+ messages in thread
* [PATCH] dm-writecache: drop the lock on an 'impossible' path
  2022-08-05  9:08 drivers/md/dm-writecache.c:1554 writecache_map() warn: inconsistent returns '&wc->lock' Dan Carpenter
@ 2022-08-08 14:50 ` Mikulas Patocka
  0 siblings, 0 replies; 2+ messages in thread
From: Mikulas Patocka @ 2022-08-08 14:50 UTC (permalink / raw)
  To: Dan Carpenter, Mike Snitzer, dm-devel
  Cc: kbuild, lkp, kbuild-all, Mike Snitzer, linux-kernel



On Fri, 5 Aug 2022, Dan Carpenter wrote:

> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   b44f2fd87919b5ae6e1756d4c7ba2cbba22238e1
> commit: df699cc16ea5ef93a917676dcdd4376e02860ad5 dm writecache: report invalid return from writecache_map helpers
> config: arc-randconfig-m041-20220804 (https://download.01.org/0day-ci/archive/20220805/202208050301.roHRxc6O-lkp@intel.com/config)
> compiler: arc-elf-gcc (GCC) 12.1.0
> 
> If you fix the issue, kindly add following tag where applicable
> Reported-by: kernel test robot <lkp@intel.com>
> Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
> 
> smatch warnings:
> drivers/md/dm-writecache.c:1554 writecache_map() warn: inconsistent returns '&wc->lock'.

Hi

Here I'm sending a patch for this warning.

Mikulas



From: Mikulas Patocka <mpatocka@redhat.com>

There's a smatch warning "inconsistent returns '&wc->lock'" in
dm-writecache. The reason for the warning is that the function
writecache_map doesn't drop the lock on the impossible path. This patch
adds wc_unlock after the BUG statement (so that it will be compiled-away
anyway) to fix the warning.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>

Index: linux-2.6/drivers/md/dm-writecache.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-writecache.c
+++ linux-2.6/drivers/md/dm-writecache.c
@@ -1598,7 +1598,8 @@ done:
 
 	default:
 		BUG();
-		return -1;
+		wc_unlock(wc);
+		return DM_MAPIO_KILL;
 	}
 }
 


^ permalink raw reply	[flat|nested] 2+ messages in thread
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2022-08-05  9:08 drivers/md/dm-writecache.c:1554 writecache_map() warn: inconsistent returns '&wc->lock' Dan Carpenter
2022-08-08 14:50 ` [PATCH] dm-writecache: drop the lock on an 'impossible' path Mikulas Patocka

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