6.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Vishal Verma vishal.l.verma@intel.com
[ Upstream commit 6f6544f27e41f9d7dca55c288f12175a9c48dfe2 ]
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 legitimately 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.
Link: https://lkml.kernel.org/r/20240430-vv-dax_abi_fixes-v3-2-e3dcd755774c@intel.... Fixes: c05ae9d85b47 ("dax/bus.c: replace driver-core lock usage by a local rwsem") Signed-off-by: Vishal Verma vishal.l.verma@intel.com Reported-by: Dan Williams dan.j.williams@intel.com Reviewed-by: Dan Williams dan.j.williams@intel.com Cc: Alison Schofield alison.schofield@intel.com Cc: Dave Jiang dave.jiang@intel.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- 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 7924dd542a139..e2c7354ce3281 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);