[PATCH V3 1/2] virtio_pmem: initialize provider_data through nd_region_desc

[PATCH V3 1/2] virtio_pmem: initialize provider_data through nd_region_desc

[Jason Wang]

We used to initialize the provider_data manually after
nvdimm_pemm_region_create(). This seems to be racy if the flush is
issued before the initialization of provider_data[1]. Fixing this by
initializing the provider_data through nd_region_desc to make sure the
provider_data is ready after the pmem is created.

[1]:

[   80.152281] nd_pmem namespace0.0: unable to guarantee persistence of writes
[   92.393956] BUG: kernel NULL pointer dereference, address: 0000000000000318
[   92.394551] #PF: supervisor read access in kernel mode
[   92.394955] #PF: error_code(0x0000) - not-present page
[   92.395365] PGD 0 P4D 0
[   92.395566] Oops: 0000 [#1] PREEMPT SMP PTI
[   92.395867] CPU: 2 PID: 506 Comm: mkfs.ext4 Not tainted 5.19.0-rc1+ #453
[   92.396365] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009),
BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
[   92.397178] RIP: 0010:virtio_pmem_flush+0x2f/0x1f0
[   92.397521] Code: 55 41 54 55 53 48 81 ec a0 00 00 00 65 48 8b 04
25 28 00 00 00 48 89 84 24 98 00 00 00 31 c0 48 8b 87 78 03 00 00 48
89 04 24 <48> 8b 98 18 03 00 00 e8 85 bf 6b 00 ba 58 00 00 00 be c0 0c
00 00
[   92.398982] RSP: 0018:ffff9a7380aefc88 EFLAGS: 00010246
[   92.399349] RAX: 0000000000000000 RBX: ffff8e77c3f86f00 RCX: 0000000000000000
[   92.399833] RDX: ffffffffad4ea720 RSI: ffff8e77c41e39c0 RDI: ffff8e77c41c5c00
[   92.400388] RBP: ffff8e77c41e39c0 R08: ffff8e77c19f0600 R09: 0000000000000000
[   92.400874] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8e77c0814e28
[   92.401364] R13: 0000000000000000 R14: 0000000000000000 R15: ffff8e77c41e39c0
[   92.401849] FS:  00007f3cd75b2780(0000) GS:ffff8e7937d00000(0000)
knlGS:0000000000000000
[   92.402423] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   92.402821] CR2: 0000000000000318 CR3: 0000000103c80002 CR4: 0000000000370ee0
[   92.403307] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[   92.403793] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[   92.404278] Call Trace:
[   92.404481]  <TASK>
[   92.404654]  ? mempool_alloc+0x5d/0x160
[   92.404939]  ? terminate_walk+0x5f/0xf0
[   92.405226]  ? bio_alloc_bioset+0xbb/0x3f0
[   92.405525]  async_pmem_flush+0x17/0x80
[   92.405806]  nvdimm_flush+0x11/0x30
[   92.406067]  pmem_submit_bio+0x1e9/0x200
[   92.406354]  __submit_bio+0x80/0x120
[   92.406621]  submit_bio_noacct_nocheck+0xdc/0x2a0
[   92.406958]  submit_bio_wait+0x4e/0x80
[   92.407234]  blkdev_issue_flush+0x31/0x50
[   92.407526]  ? punt_bios_to_rescuer+0x230/0x230
[   92.407852]  blkdev_fsync+0x1e/0x30
[   92.408112]  do_fsync+0x33/0x70
[   92.408354]  __x64_sys_fsync+0xb/0x10
[   92.408625]  do_syscall_64+0x43/0x90
[   92.408895]  entry_SYSCALL_64_after_hwframe+0x46/0xb0
[   92.409257] RIP: 0033:0x7f3cd76c6c44

Fixes 6e84200c0a29 ("virtio-pmem: Add virtio pmem driver")
Acked-by: Pankaj Gupta <pankaj.gupta@amd.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
Changes since V1:
- Add calltrace to explain the issue in detail
---
 drivers/nvdimm/virtio_pmem.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/nvdimm/virtio_pmem.c b/drivers/nvdimm/virtio_pmem.c
index 995b6cdc67ed..48f8327d0431 100644
--- a/drivers/nvdimm/virtio_pmem.c
+++ b/drivers/nvdimm/virtio_pmem.c
@@ -81,6 +81,7 @@ static int virtio_pmem_probe(struct virtio_device *vdev)
 	ndr_desc.res = &res;
 	ndr_desc.numa_node = nid;
 	ndr_desc.flush = async_pmem_flush;
+	ndr_desc.provider_data = vdev;
 	set_bit(ND_REGION_PAGEMAP, &ndr_desc.flags);
 	set_bit(ND_REGION_ASYNC, &ndr_desc.flags);
 	nd_region = nvdimm_pmem_region_create(vpmem->nvdimm_bus, &ndr_desc);
@@ -89,7 +90,6 @@ static int virtio_pmem_probe(struct virtio_device *vdev)
 		err = -ENXIO;
 		goto out_nd;
 	}
-	nd_region->provider_data = dev_to_virtio(nd_region->dev.parent->parent);
 	return 0;
 out_nd:
 	nvdimm_bus_unregister(vpmem->nvdimm_bus);
-- 
2.25.1

[PATCH V3 2/2] virtio_pmem: set device ready in probe()

[Jason Wang]

The NVDIMM region could be available before the virtio_device_ready()
that is called by virtio_dev_probe(). This means the driver tries to
use device before DRIVER_OK which violates the spec, fixing this by
set device ready before the nvdimm_pmem_region_create().

Note that this means the virtio_pmem_host_ack() could be triggered
before the creation of the nd region, this is safe since the pmem_lock
has been initialized and whether or not any available buffer is added
before is validated by virtio_pmem_host_ack().

Fixes 6e84200c0a29 ("virtio-pmem: Add virtio pmem driver")
Acked-by: Pankaj Gupta <pankaj.gupta@amd.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
Changes since V2:
- Tweak the change log
Changes since v1:
- Remove some comments per Dan
---
 drivers/nvdimm/virtio_pmem.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/nvdimm/virtio_pmem.c b/drivers/nvdimm/virtio_pmem.c
index 48f8327d0431..20da455d2ef6 100644
--- a/drivers/nvdimm/virtio_pmem.c
+++ b/drivers/nvdimm/virtio_pmem.c
@@ -84,6 +84,12 @@ static int virtio_pmem_probe(struct virtio_device *vdev)
 	ndr_desc.provider_data = vdev;
 	set_bit(ND_REGION_PAGEMAP, &ndr_desc.flags);
 	set_bit(ND_REGION_ASYNC, &ndr_desc.flags);
+	/*
+	 * The NVDIMM region could be available before the
+	 * virtio_device_ready() that is called by
+	 * virtio_dev_probe(), so we set device ready here.
+	 */
+	virtio_device_ready(vdev);
 	nd_region = nvdimm_pmem_region_create(vpmem->nvdimm_bus, &ndr_desc);
 	if (!nd_region) {
 		dev_err(&vdev->dev, "failed to create nvdimm region\n");
@@ -92,6 +98,7 @@ static int virtio_pmem_probe(struct virtio_device *vdev)
 	}
 	return 0;
 out_nd:
+	virtio_reset_device(vdev);
 	nvdimm_bus_unregister(vpmem->nvdimm_bus);
 out_vq:
 	vdev->config->del_vqs(vdev);
-- 
2.25.1