[PATCH V2 1/1] nvme: fix multiple ctrl removal scheduling

[Rakesh Pandit]

Commit c5f6ce97c1210 tries to address multiple resets but fails as
work_busy doesn't involve any synchronization and can fail.  This is
reproducible easily as can be seen by WARNING below which is triggered
with line:

WARN_ON(dev->ctrl.state == NVME_CTRL_RESETTING)

Allowing multiple resets can result in multiple controller removal as
well if different conditions inside nvme_reset_work fail and which
might deadlock on device_release_driver.

This patch makes sure that work queue item (reset_work) is added only
if controller state != NVME_CTRL_RESETTING and that is achieved by
moving state change outside nvme_reset_work into nvme_reset and
removing old work_busy call.  State change is always synchronizated
using controller spinlock.

[  480.327007] WARNING: CPU: 3 PID: 150 at drivers/nvme/host/pci.c:1900 nvme_reset_work+0x36c/0xec0
[  480.327008] Modules linked in: rfcomm fuse nf_conntrack_netbios_ns nf_conntrack_broadcast...
[  480.327044]  btusb videobuf2_core ghash_clmulni_intel snd_hwdep cfg80211 acer_wmi hci_uart..
[  480.327065] CPU: 3 PID: 150 Comm: kworker/u16:2 Not tainted 4.12.0-rc1+ #13
[  480.327065] Hardware name: Acer Predator G9-591/Mustang_SLS, BIOS V1.10 03/03/2016
[  480.327066] Workqueue: nvme nvme_reset_work
[  480.327067] task: ffff880498ad8000 task.stack: ffffc90002218000
[  480.327068] RIP: 0010:nvme_reset_work+0x36c/0xec0
[  480.327069] RSP: 0018:ffffc9000221bdb8 EFLAGS: 00010246
[  480.327070] RAX: 0000000000460000 RBX: ffff880498a98128 RCX: dead000000000200
[  480.327070] RDX: 0000000000000001 RSI: ffff8804b1028020 RDI: ffff880498a98128
[  480.327071] RBP: ffffc9000221be50 R08: 0000000000000000 R09: 0000000000000000
[  480.327071] R10: ffffc90001963ce8 R11: 000000000000020d R12: ffff880498a98000
[  480.327072] R13: ffff880498a53500 R14: ffff880498a98130 R15: ffff880498a98128
[  480.327072] FS:  0000000000000000(0000) GS:ffff8804c1cc0000(0000) knlGS:0000000000000000
[  480.327073] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  480.327074] CR2: 00007ffcf3c37f78 CR3: 0000000001e09000 CR4: 00000000003406e0
[  480.327074] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  480.327075] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  480.327075] Call Trace:
[  480.327079]  ? __switch_to+0x227/0x400
[  480.327081]  process_one_work+0x18c/0x3a0
[  480.327082]  worker_thread+0x4e/0x3b0
[  480.327084]  kthread+0x109/0x140
[  480.327085]  ? process_one_work+0x3a0/0x3a0
[  480.327087]  ? kthread_park+0x60/0x60
[  480.327102]  ret_from_fork+0x2c/0x40
[  480.327103] Code: e8 5a dc ff ff 85 c0 41 89 c1 0f.....

V2: Use controller state to solve the problem (suggested by Christoph Hellwig)
Fixes: c5f6ce97c1210 ("nvme: don't schedule multiple resets")
Signed-off-by: Rakesh Pandit <rakesh at tuxera.com>
---
 drivers/nvme/host/pci.c | 10 ++--------
 1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 4c2ff2b..ba54e2a 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -1903,9 +1903,6 @@ static void nvme_reset_work(struct work_struct *work)
 	bool was_suspend = !!(dev->ctrl.ctrl_config & NVME_CC_SHN_NORMAL);
 	int result = -ENODEV;
 
-	if (WARN_ON(dev->ctrl.state == NVME_CTRL_RESETTING))
-		goto out;
-
 	/*
 	 * If we're called to reset a live controller first shut it down before
 	 * moving on.
@@ -1913,9 +1910,6 @@ static void nvme_reset_work(struct work_struct *work)
 	if (dev->ctrl.ctrl_config & NVME_CC_ENABLE)
 		nvme_dev_disable(dev, false);
 
-	if (!nvme_change_ctrl_state(&dev->ctrl, NVME_CTRL_RESETTING))
-		goto out;
-
 	result = nvme_pci_enable(dev);
 	if (result)
 		goto out;
@@ -2009,8 +2003,8 @@ static int nvme_reset(struct nvme_dev *dev)
 {
 	if (!dev->ctrl.admin_q || blk_queue_dying(dev->ctrl.admin_q))
 		return -ENODEV;
-	if (work_busy(&dev->reset_work))
-		return -ENODEV;
+	if (!nvme_change_ctrl_state(&dev->ctrl, NVME_CTRL_RESETTING))
+		return -EBUSY;
 	if (!queue_work(nvme_workq, &dev->reset_work))
 		return -EBUSY;
 	return 0;
-- 
2.5.5