Commit 4d66e5e9 authored Jun 10, 2015 by Dan Williams Committed by Jens Axboe Jun 11, 2015

block: fix ext_dev_lock lockdep report



 =================================
 [ 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: 2da78092 "block:
Fix dev_t minor allocation lifetime".  Both this and 2da78092 are
candidates for -stable.

Fixes: 2da78092 ("block: Fix dev_t minor allocation lifetime")
Cc: <stable@vger.kernel.org>
Cc: Keith Busch <keith.busch@intel.com>
Reported-by: NeilBrown <neilb@suse.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

parent c3b4afca

block/genhd.c

+6 −6

Original line number	Diff line number	Diff line
		@@ -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);
		}
		}

		@@ -690,13 +690,13 @@ 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;

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