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authorIra Weiny <ira.weiny@intel.com>2020-10-13 16:52:33 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-10-13 18:38:30 -0700
commit433e7d3177544c8cf0b6375abd310b0ef023fe9d (patch)
tree3afd4553d29a14577a9caa53caaca2b78de85156 /mm/memremap.c
parent822bca52ee7eb279acfba261a423ed7ac47d6f73 (diff)
downloadlinux-433e7d3177544c8cf0b6375abd310b0ef023fe9d.tar.bz2
mm/memremap.c: convert devmap static branch to {inc,dec}
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-ass.net/ Signed-off-by: Ira Weiny <ira.weiny@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: William Kucharski <william.kucharski@oracle.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Vishal Verma <vishal.l.verma@intel.com> Link: https://lkml.kernel.org/r/20200810235319.2796597-1-ira.weiny@intel.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/memremap.c')
-rw-r--r--mm/memremap.c7
1 files changed, 2 insertions, 5 deletions
diff --git a/mm/memremap.c b/mm/memremap.c
index 7dc7aec971de..198083453182 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