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dax/bus.c: fix locking for unregister_dax_dev / unregister_dax_mapping paths

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Commit c05ae9d85b ("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.com
Fixes: c05ae9d85b ("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>
This commit is contained in:
Vishal Verma 2024-04-30 11:44:24 -06:00 committed by Andrew Morton
parent c14c647bbe
commit 6f6544f27e
1 changed files with 8 additions and 34 deletions
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42
drivers/dax/bus.c
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@ -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);