Commit Fixes: c05ae9d85b47 ("dax/bus.c: replace driver-core lock usage by a local rwsem")
introduced a few problems that this series aims to fix. Add back
device_lock() where it was correctly used (during device manipulation
operations), remove conditional locking in unregister_dax_dev() and
unregister_dax_mapping(), use non-interruptible versions of rwsem
locks when not called from a user process, and fix up a write vs.
read usage of an rwsem.
Signed-off-by: Vishal Verma <[email protected]>
---
Changes in v3:
- Rebase to v6.9-rc6
- Collect review tags (Dan)
- Reword commit message for patch 2 (Dan)
- Use plain down_write() in delete_store() (Dan)
- Link to v2: https://lore.kernel.org/r/[email protected]
Changes in v2:
- Add back valid device_lock uses (Dan)
- Remove conditional locking (Dan)
- Use non-interruptible versions of rwsem locks when not called from a
user process (Dan)
- Fix up a write vs. read usage of an rwsem
- Link to v1: https://lore.kernel.org/r/[email protected]
---
Vishal Verma (4):
dax/bus.c: replace WARN_ON_ONCE() with lockdep asserts
dax/bus.c: fix locking for unregister_dax_dev / unregister_dax_mapping paths
dax/bus.c: Don't use down_write_killable for non-user processes
dax/bus.c: Use the right locking mode (read vs write) in size_show
drivers/dax/bus.c | 66 +++++++++++++++----------------------------------------
1 file changed, 18 insertions(+), 48 deletions(-)
---
base-commit: e67572cd2204894179d89bd7b984072f19313b03
change-id: 20240402-vv-dax_abi_fixes-8af3b6ff2e5a
Best regards,
--
Vishal Verma <[email protected]>
In [1], Dan points out that all of the WARN_ON_ONCE() usage in the
referenced patch should be replaced with lockdep_assert_held, or
lockdep_held_assert_write(). Replace these as appropriate.
Link: https://lore.kernel.org/r/65f0b5ef41817_aa222941a@dwillia2-mobl3.amr.corp.intel.com.notmuch [1]
Fixes: c05ae9d85b47 ("dax/bus.c: replace driver-core lock usage by a local rwsem")
Cc: Andrew Morton <[email protected]>
Reported-by: Dan Williams <[email protected]>
Reviewed-by: Dan Williams <[email protected]>
Signed-off-by: Vishal Verma <[email protected]>
---
drivers/dax/bus.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)
diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
index 797e1ebff299..7924dd542a13 100644
--- a/drivers/dax/bus.c
+++ b/drivers/dax/bus.c
@@ -192,7 +192,7 @@ static u64 dev_dax_size(struct dev_dax *dev_dax)
u64 size = 0;
int i;
- WARN_ON_ONCE(!rwsem_is_locked(&dax_dev_rwsem));
+ lockdep_assert_held(&dax_dev_rwsem);
for (i = 0; i < dev_dax->nr_range; i++)
size += range_len(&dev_dax->ranges[i].range);
@@ -302,7 +302,7 @@ static unsigned long long dax_region_avail_size(struct dax_region *dax_region)
resource_size_t size = resource_size(&dax_region->res);
struct resource *res;
- WARN_ON_ONCE(!rwsem_is_locked(&dax_region_rwsem));
+ lockdep_assert_held(&dax_region_rwsem);
for_each_dax_region_resource(dax_region, res)
size -= resource_size(res);
@@ -447,7 +447,7 @@ static void trim_dev_dax_range(struct dev_dax *dev_dax)
struct range *range = &dev_dax->ranges[i].range;
struct dax_region *dax_region = dev_dax->region;
- WARN_ON_ONCE(!rwsem_is_locked(&dax_region_rwsem));
+ lockdep_assert_held_write(&dax_region_rwsem);
dev_dbg(&dev_dax->dev, "delete range[%d]: %#llx:%#llx\n", i,
(unsigned long long)range->start,
(unsigned long long)range->end);
@@ -507,7 +507,7 @@ static int __free_dev_dax_id(struct dev_dax *dev_dax)
struct dax_region *dax_region;
int rc = dev_dax->id;
- WARN_ON_ONCE(!rwsem_is_locked(&dax_dev_rwsem));
+ lockdep_assert_held_write(&dax_dev_rwsem);
if (!dev_dax->dyn_id || dev_dax->id < 0)
return -1;
@@ -713,7 +713,7 @@ static void __unregister_dax_mapping(void *data)
dev_dbg(dev, "%s\n", __func__);
- WARN_ON_ONCE(!rwsem_is_locked(&dax_region_rwsem));
+ lockdep_assert_held_write(&dax_region_rwsem);
dev_dax->ranges[mapping->range_id].mapping = NULL;
mapping->range_id = -1;
@@ -830,7 +830,7 @@ static int devm_register_dax_mapping(struct dev_dax *dev_dax, int range_id)
struct device *dev;
int rc;
- WARN_ON_ONCE(!rwsem_is_locked(&dax_region_rwsem));
+ lockdep_assert_held_write(&dax_region_rwsem);
if (dev_WARN_ONCE(&dev_dax->dev, !dax_region->dev->driver,
"region disabled\n"))
@@ -876,7 +876,7 @@ static int alloc_dev_dax_range(struct dev_dax *dev_dax, u64 start,
struct resource *alloc;
int i, rc;
- WARN_ON_ONCE(!rwsem_is_locked(&dax_region_rwsem));
+ lockdep_assert_held_write(&dax_region_rwsem);
/* handle the seed alloc special case */
if (!size) {
@@ -935,7 +935,7 @@ static int adjust_dev_dax_range(struct dev_dax *dev_dax, struct resource *res, r
struct device *dev = &dev_dax->dev;
int rc;
- WARN_ON_ONCE(!rwsem_is_locked(&dax_region_rwsem));
+ lockdep_assert_held_write(&dax_region_rwsem);
if (dev_WARN_ONCE(dev, !size, "deletion is handled by dev_dax_shrink\n"))
return -EINVAL;
--
2.44.0
Change an instance of down_write_killable() to a simple down_write() where
there is no user process that might want to interrupt the operation.
Fixes: c05ae9d85b47 ("dax/bus.c: replace driver-core lock usage by a local rwsem")
Reported-by: Dan Williams <[email protected]>
Reviewed-by: Dan Williams <[email protected]>
Signed-off-by: Vishal Verma <[email protected]>
---
drivers/dax/bus.c | 6 +-----
1 file changed, 1 insertion(+), 5 deletions(-)
diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
index e2c7354ce328..0011a6e6a8f2 100644
--- a/drivers/dax/bus.c
+++ b/drivers/dax/bus.c
@@ -1540,12 +1540,8 @@ static struct dev_dax *__devm_create_dev_dax(struct dev_dax_data *data)
struct dev_dax *devm_create_dev_dax(struct dev_dax_data *data)
{
struct dev_dax *dev_dax;
- int rc;
-
- rc = down_write_killable(&dax_region_rwsem);
- if (rc)
- return ERR_PTR(rc);
+ down_write(&dax_region_rwsem);
dev_dax = __devm_create_dev_dax(data);
up_write(&dax_region_rwsem);
--
2.44.0
In size_show(), the dax_dev_rwsem only needs a read lock, but was
acquiring a write lock. Change it to down_read_interruptible() so it
doesn't unnecessarily hold a write lock.
Fixes: c05ae9d85b47 ("dax/bus.c: replace driver-core lock usage by a local rwsem")
Cc: Dan Williams <[email protected]>
Reviewed-by: Dan Williams <[email protected]>
Signed-off-by: Vishal Verma <[email protected]>
---
drivers/dax/bus.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
index 0011a6e6a8f2..f24b67c64d5e 100644
--- a/drivers/dax/bus.c
+++ b/drivers/dax/bus.c
@@ -937,11 +937,11 @@ static ssize_t size_show(struct device *dev,
unsigned long long size;
int rc;
- rc = down_write_killable(&dax_dev_rwsem);
+ rc = down_read_interruptible(&dax_dev_rwsem);
if (rc)
return rc;
size = dev_dax_size(dev_dax);
- up_write(&dax_dev_rwsem);
+ up_read(&dax_dev_rwsem);
return sysfs_emit(buf, "%llu\n", size);
}
--
2.44.0
Commit c05ae9d85b47 ("dax/bus.c: replace driver-core lock usage by a local rwsem")
aimed to undo device_lock() abuses for protecting changes to dax-driver
internal data-structures like the dax_region resource tree to
device-dax-instance range structures. However, the device_lock() was
legitamately enforcing that devices to be deleted were not current
actively attached to any driver nor assigned any capacity from the
region.
As a result of the device_lock restoration in delete_store(), the
conditional locking in unregister_dev_dax() and unregister_dax_mapping()
can be removed.
Fixes: c05ae9d85b47 ("dax/bus.c: replace driver-core lock usage by a local rwsem")
Reported-by: Dan Williams <[email protected]>
Reviewed-by: Dan Williams <[email protected]>
Signed-off-by: Vishal Verma <[email protected]>
---
drivers/dax/bus.c | 42 ++++++++----------------------------------
1 file changed, 8 insertions(+), 34 deletions(-)
diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
index 7924dd542a13..e2c7354ce328 100644
--- a/drivers/dax/bus.c
+++ b/drivers/dax/bus.c
@@ -465,26 +465,17 @@ static void free_dev_dax_ranges(struct dev_dax *dev_dax)
trim_dev_dax_range(dev_dax);
}
-static void __unregister_dev_dax(void *dev)
+static void unregister_dev_dax(void *dev)
{
struct dev_dax *dev_dax = to_dev_dax(dev);
dev_dbg(dev, "%s\n", __func__);
+ down_write(&dax_region_rwsem);
kill_dev_dax(dev_dax);
device_del(dev);
free_dev_dax_ranges(dev_dax);
put_device(dev);
-}
-
-static void unregister_dev_dax(void *dev)
-{
- if (rwsem_is_locked(&dax_region_rwsem))
- return __unregister_dev_dax(dev);
-
- if (WARN_ON_ONCE(down_write_killable(&dax_region_rwsem) != 0))
- return;
- __unregister_dev_dax(dev);
up_write(&dax_region_rwsem);
}
@@ -560,15 +551,10 @@ static ssize_t delete_store(struct device *dev, struct device_attribute *attr,
if (!victim)
return -ENXIO;
- rc = down_write_killable(&dax_region_rwsem);
- if (rc)
- return rc;
- rc = down_write_killable(&dax_dev_rwsem);
- if (rc) {
- up_write(&dax_region_rwsem);
- return rc;
- }
+ device_lock(dev);
+ device_lock(victim);
dev_dax = to_dev_dax(victim);
+ down_write(&dax_dev_rwsem);
if (victim->driver || dev_dax_size(dev_dax))
rc = -EBUSY;
else {
@@ -589,11 +575,12 @@ static ssize_t delete_store(struct device *dev, struct device_attribute *attr,
rc = -EBUSY;
}
up_write(&dax_dev_rwsem);
+ device_unlock(victim);
/* won the race to invalidate the device, clean it up */
if (do_del)
devm_release_action(dev, unregister_dev_dax, victim);
- up_write(&dax_region_rwsem);
+ device_unlock(dev);
put_device(victim);
return rc;
@@ -705,7 +692,7 @@ static void dax_mapping_release(struct device *dev)
put_device(parent);
}
-static void __unregister_dax_mapping(void *data)
+static void unregister_dax_mapping(void *data)
{
struct device *dev = data;
struct dax_mapping *mapping = to_dax_mapping(dev);
@@ -713,25 +700,12 @@ static void __unregister_dax_mapping(void *data)
dev_dbg(dev, "%s\n", __func__);
- lockdep_assert_held_write(&dax_region_rwsem);
-
dev_dax->ranges[mapping->range_id].mapping = NULL;
mapping->range_id = -1;
device_unregister(dev);
}
-static void unregister_dax_mapping(void *data)
-{
- if (rwsem_is_locked(&dax_region_rwsem))
- return __unregister_dax_mapping(data);
-
- if (WARN_ON_ONCE(down_write_killable(&dax_region_rwsem) != 0))
- return;
- __unregister_dax_mapping(data);
- up_write(&dax_region_rwsem);
-}
-
static struct dev_dax_range *get_dax_range(struct device *dev)
{
struct dax_mapping *mapping = to_dax_mapping(dev);
--
2.44.0