[PATCH 3.16.y-ckt 61/71] block: fix ext_dev_lock lockdep report

[Luis Henriques]

3.16.7-ckt14 -stable review patch.  If anyone has any objections, please let me know.

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

From: Dan Williams <dan.j.williams at intel.com>

commit 4d66e5e9b6d720d8463e11d027bd4ad91c8b1318 upstream.

 =================================
 [ INFO: inconsistent lock state ]
 4.1.0-rc7+ #217 Tainted: G           O
 ---------------------------------
 inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.
 swapper/6/0 [HC0[0]:SC1[1]:HE1:SE0] takes:
  (ext_devt_lock){+.?...}, at: [<ffffffff8143a60c>] blk_free_devt+0x3c/0x70
 {SOFTIRQ-ON-W} state was registered at:
   [<ffffffff810bf6b1>] __lock_acquire+0x461/0x1e70
   [<ffffffff810c1947>] lock_acquire+0xb7/0x290
   [<ffffffff818ac3a8>] _raw_spin_lock+0x38/0x50
   [<ffffffff8143a07d>] blk_alloc_devt+0x6d/0xd0  <-- take the lock in process context
[..]
  [<ffffffff810bf64e>] __lock_acquire+0x3fe/0x1e70
  [<ffffffff810c00ad>] ? __lock_acquire+0xe5d/0x1e70
  [<ffffffff810c1947>] lock_acquire+0xb7/0x290
  [<ffffffff8143a60c>] ? blk_free_devt+0x3c/0x70
  [<ffffffff818ac3a8>] _raw_spin_lock+0x38/0x50
  [<ffffffff8143a60c>] ? blk_free_devt+0x3c/0x70
  [<ffffffff8143a60c>] blk_free_devt+0x3c/0x70    <-- take the lock in softirq
  [<ffffffff8143bfec>] part_release+0x1c/0x50
  [<ffffffff8158edf6>] device_release+0x36/0xb0
  [<ffffffff8145ac2b>] kobject_cleanup+0x7b/0x1a0
  [<ffffffff8145aad0>] kobject_put+0x30/0x70
  [<ffffffff8158f147>] put_device+0x17/0x20
  [<ffffffff8143c29c>] delete_partition_rcu_cb+0x16c/0x180
  [<ffffffff8143c130>] ? read_dev_sector+0xa0/0xa0
  [<ffffffff810e0e0f>] rcu_process_callbacks+0x2ff/0xa90
  [<ffffffff810e0dcf>] ? rcu_process_callbacks+0x2bf/0xa90
  [<ffffffff81067e2e>] __do_softirq+0xde/0x600

Neil sees this in his tests and it also triggers on pmem driver unbind
for the libnvdimm tests.  This fix is on top of an initial fix by Keith
for incorrect usage of mutex_lock() in this path: 2da78092dda1 "block:
Fix dev_t minor allocation lifetime".  Both this and 2da78092dda1 are
candidates for -stable.

Fixes: 2da78092dda1 ("block: Fix dev_t minor allocation lifetime")
Cc: Keith Busch <keith.busch at intel.com>
Reported-by: NeilBrown <neilb at suse.de>
Signed-off-by: Dan Williams <dan.j.williams at intel.com>
Signed-off-by: Jens Axboe <axboe at fb.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 block/genhd.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/block/genhd.c b/block/genhd.c
index a8d586a729bb..9316f5fd416f 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -422,9 +422,9 @@ int blk_alloc_devt(struct hd_struct *part, dev_t *devt)
 	/* allocate ext devt */
 	idr_preload(GFP_KERNEL);
 
-	spin_lock(&ext_devt_lock);
+	spin_lock_bh(&ext_devt_lock);
 	idx = idr_alloc(&ext_devt_idr, part, 0, NR_EXT_DEVT, GFP_NOWAIT);
-	spin_unlock(&ext_devt_lock);
+	spin_unlock_bh(&ext_devt_lock);
 
 	idr_preload_end();
 	if (idx < 0)
@@ -449,9 +449,9 @@ void blk_free_devt(dev_t devt)
 		return;
 
 	if (MAJOR(devt) == BLOCK_EXT_MAJOR) {
-		spin_lock(&ext_devt_lock);
+		spin_lock_bh(&ext_devt_lock);
 		idr_remove(&ext_devt_idr, blk_mangle_minor(MINOR(devt)));
-		spin_unlock(&ext_devt_lock);
+		spin_unlock_bh(&ext_devt_lock);
 	}
 }
 
@@ -691,13 +691,13 @@ struct gendisk *get_gendisk(dev_t devt, int *partno)
 	} else {
 		struct hd_struct *part;
 
-		spin_lock(&ext_devt_lock);
+		spin_lock_bh(&ext_devt_lock);
 		part = idr_find(&ext_devt_idr, blk_mangle_minor(MINOR(devt)));
 		if (part && get_disk(part_to_disk(part))) {
 			*partno = part->partno;
 			disk = part_to_disk(part);
 		}
-		spin_unlock(&ext_devt_lock);
+		spin_unlock_bh(&ext_devt_lock);
 	}
 
 	return disk;