From: ira.weiny@intel.com
To: Andrew Morton <akpm@linux-foundation.org>,
Vishal Verma <vishal.l.verma@intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>,
Dan Williams <dan.j.williams@intel.com>,
"Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: [PATCH] memremap: Convert devmap static branch to {inc,dec}
Date: Mon, 10 Aug 2020 16:53:19 -0700 [thread overview]
Message-ID: <20200810235319.2796597-1-ira.weiny@intel.com> (raw)
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-ass.net/
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: 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
--
2.28.0.rc0.12.gb6a658bd00c9
next reply other threads:[~2020-08-10 23:53 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-10 23:53 ira.weiny [this message]
2020-08-11 11:59 ` [PATCH] memremap: Convert devmap static branch to {inc,dec} William Kucharski
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