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Subject[PATCH 4/6] libnvdimm/bus: Stop holding nvdimm_bus_list_mutex over __nd_ioctl()
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Date
In preparation for fixing a deadlock between wait_for_bus_probe_idle()
and the nvdimm_bus_list_mutex arrange for __nd_ioctl() without
nvdimm_bus_list_mutex held. This also unifies the 'dimm' and 'bus' level
ioctls into a common nd_ioctl() preamble implementation.

Marked for -stable as it is a pre-requisite for a follow-on fix.

Cc: <stable@vger.kernel.org>
Fixes: bf9bccc14c05 ("libnvdimm: pmem label sets and namespace instantiation")
Cc: Vishal Verma <vishal.l.verma@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
drivers/nvdimm/bus.c | 96 ++++++++++++++++++++++++++++------------------
drivers/nvdimm/nd-core.h | 3 +
2 files changed, 60 insertions(+), 39 deletions(-)

diff --git a/drivers/nvdimm/bus.c b/drivers/nvdimm/bus.c
index 42713b210f51..dfb93228d6a7 100644
--- a/drivers/nvdimm/bus.c
+++ b/drivers/nvdimm/bus.c
@@ -73,7 +73,7 @@ static void nvdimm_bus_probe_end(struct nvdimm_bus *nvdimm_bus)
{
nvdimm_bus_lock(&nvdimm_bus->dev);
if (--nvdimm_bus->probe_active == 0)
- wake_up(&nvdimm_bus->probe_wait);
+ wake_up(&nvdimm_bus->wait);
nvdimm_bus_unlock(&nvdimm_bus->dev);
}

@@ -341,7 +341,7 @@ struct nvdimm_bus *nvdimm_bus_register(struct device *parent,
return NULL;
INIT_LIST_HEAD(&nvdimm_bus->list);
INIT_LIST_HEAD(&nvdimm_bus->mapping_list);
- init_waitqueue_head(&nvdimm_bus->probe_wait);
+ init_waitqueue_head(&nvdimm_bus->wait);
nvdimm_bus->id = ida_simple_get(&nd_ida, 0, 0, GFP_KERNEL);
if (nvdimm_bus->id < 0) {
kfree(nvdimm_bus);
@@ -426,6 +426,9 @@ static int nd_bus_remove(struct device *dev)
list_del_init(&nvdimm_bus->list);
mutex_unlock(&nvdimm_bus_list_mutex);

+ wait_event(nvdimm_bus->wait,
+ atomic_read(&nvdimm_bus->ioctl_active) == 0);
+
nd_synchronize();
device_for_each_child(&nvdimm_bus->dev, NULL, child_unregister);

@@ -885,7 +888,7 @@ void wait_nvdimm_bus_probe_idle(struct device *dev)
if (nvdimm_bus->probe_active == 0)
break;
nvdimm_bus_unlock(&nvdimm_bus->dev);
- wait_event(nvdimm_bus->probe_wait,
+ wait_event(nvdimm_bus->wait,
nvdimm_bus->probe_active == 0);
nvdimm_bus_lock(&nvdimm_bus->dev);
} while (true);
@@ -1115,24 +1118,10 @@ static int __nd_ioctl(struct nvdimm_bus *nvdimm_bus, struct nvdimm *nvdimm,
return rc;
}

-static long nd_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
-{
- long id = (long) file->private_data;
- int rc = -ENXIO, ro;
- struct nvdimm_bus *nvdimm_bus;
-
- ro = ((file->f_flags & O_ACCMODE) == O_RDONLY);
- mutex_lock(&nvdimm_bus_list_mutex);
- list_for_each_entry(nvdimm_bus, &nvdimm_bus_list, list) {
- if (nvdimm_bus->id == id) {
- rc = __nd_ioctl(nvdimm_bus, NULL, ro, cmd, arg);
- break;
- }
- }
- mutex_unlock(&nvdimm_bus_list_mutex);
-
- return rc;
-}
+enum nd_ioctl_mode {
+ BUS_IOCTL,
+ DIMM_IOCTL,
+};

static int match_dimm(struct device *dev, void *data)
{
@@ -1147,31 +1136,62 @@ static int match_dimm(struct device *dev, void *data)
return 0;
}

-static long nvdimm_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+static long nd_ioctl(struct file *file, unsigned int cmd, unsigned long arg,
+ enum nd_ioctl_mode mode)
+
{
- int rc = -ENXIO, ro;
- struct nvdimm_bus *nvdimm_bus;
+ struct nvdimm_bus *nvdimm_bus, *found = NULL;
+ long id = (long) file->private_data;
+ struct nvdimm *nvdimm = NULL;
+ int rc, ro;

ro = ((file->f_flags & O_ACCMODE) == O_RDONLY);
mutex_lock(&nvdimm_bus_list_mutex);
list_for_each_entry(nvdimm_bus, &nvdimm_bus_list, list) {
- struct device *dev = device_find_child(&nvdimm_bus->dev,
- file->private_data, match_dimm);
- struct nvdimm *nvdimm;
-
- if (!dev)
- continue;
+ if (mode == DIMM_IOCTL) {
+ struct device *dev;
+
+ dev = device_find_child(&nvdimm_bus->dev,
+ file->private_data, match_dimm);
+ if (!dev)
+ continue;
+ nvdimm = to_nvdimm(dev);
+ found = nvdimm_bus;
+ } else if (nvdimm_bus->id == id) {
+ found = nvdimm_bus;
+ }

- nvdimm = to_nvdimm(dev);
- rc = __nd_ioctl(nvdimm_bus, nvdimm, ro, cmd, arg);
- put_device(dev);
- break;
+ if (found) {
+ atomic_inc(&nvdimm_bus->ioctl_active);
+ break;
+ }
}
mutex_unlock(&nvdimm_bus_list_mutex);

+ if (!found)
+ return -ENXIO;
+
+ nvdimm_bus = found;
+ rc = __nd_ioctl(nvdimm_bus, nvdimm, ro, cmd, arg);
+
+ if (nvdimm)
+ put_device(&nvdimm->dev);
+ if (atomic_dec_and_test(&nvdimm_bus->ioctl_active))
+ wake_up(&nvdimm_bus->wait);
+
return rc;
}

+static long bus_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+ return nd_ioctl(file, cmd, arg, BUS_IOCTL);
+}
+
+static long dimm_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+ return nd_ioctl(file, cmd, arg, DIMM_IOCTL);
+}
+
static int nd_open(struct inode *inode, struct file *file)
{
long minor = iminor(inode);
@@ -1183,16 +1203,16 @@ static int nd_open(struct inode *inode, struct file *file)
static const struct file_operations nvdimm_bus_fops = {
.owner = THIS_MODULE,
.open = nd_open,
- .unlocked_ioctl = nd_ioctl,
- .compat_ioctl = nd_ioctl,
+ .unlocked_ioctl = bus_ioctl,
+ .compat_ioctl = bus_ioctl,
.llseek = noop_llseek,
};

static const struct file_operations nvdimm_fops = {
.owner = THIS_MODULE,
.open = nd_open,
- .unlocked_ioctl = nvdimm_ioctl,
- .compat_ioctl = nvdimm_ioctl,
+ .unlocked_ioctl = dimm_ioctl,
+ .compat_ioctl = dimm_ioctl,
.llseek = noop_llseek,
};

diff --git a/drivers/nvdimm/nd-core.h b/drivers/nvdimm/nd-core.h
index 391e88de3a29..6cd470547106 100644
--- a/drivers/nvdimm/nd-core.h
+++ b/drivers/nvdimm/nd-core.h
@@ -17,10 +17,11 @@ extern struct workqueue_struct *nvdimm_wq;

struct nvdimm_bus {
struct nvdimm_bus_descriptor *nd_desc;
- wait_queue_head_t probe_wait;
+ wait_queue_head_t wait;
struct list_head list;
struct device dev;
int id, probe_active;
+ atomic_t ioctl_active;
struct list_head mapping_list;
struct mutex reconfig_mutex;
struct badrange badrange;
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