From: Ira Weiny ira.weiny@intel.com
While reviewing Protection Key Supervisor support it was pointed out that using a counter to track static branch enable was an anti-pattern which was better solved using the provided static_branch_{inc,dec} functions.[1]
Fix up devmap_managed_key to work the same way. Also this should be safer because there is a very small (very unlikely) race when multiple callers try to enable at the same time.
[1] https://lore.kernel.org/lkml/20200714194031.GI5523@worktop.programming.kicks...
To: Dan Williams dan.j.williams@intel.com To: Vishal Verma vishal.l.verma@intel.com Signed-off-by: Ira Weiny ira.weiny@intel.com --- mm/memremap.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-)
diff --git a/mm/memremap.c b/mm/memremap.c index 03e38b7a38f1..9fb9ad500e78 100644 --- a/mm/memremap.c +++ b/mm/memremap.c @@ -40,12 +40,10 @@ EXPORT_SYMBOL_GPL(memremap_compat_align); #ifdef CONFIG_DEV_PAGEMAP_OPS DEFINE_STATIC_KEY_FALSE(devmap_managed_key); EXPORT_SYMBOL(devmap_managed_key); -static atomic_t devmap_managed_enable;
static void devmap_managed_enable_put(void) { - if (atomic_dec_and_test(&devmap_managed_enable)) - static_branch_disable(&devmap_managed_key); + static_branch_dec(&devmap_managed_key); }
static int devmap_managed_enable_get(struct dev_pagemap *pgmap) @@ -56,8 +54,7 @@ static int devmap_managed_enable_get(struct dev_pagemap *pgmap) return -EINVAL; }
- if (atomic_inc_return(&devmap_managed_enable) == 1) - static_branch_enable(&devmap_managed_key); + static_branch_inc(&devmap_managed_key); return 0; } #else