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authorLinus Torvalds <torvalds@linux-foundation.org>2015-01-09 15:19:03 -0800
committerAl Viro <viro@zeniv.linux.org.uk>2015-01-25 23:16:29 -0500
commit360f54796ed65939093ae373b92ebd5ef3341776 (patch)
treeb89eeed53d0f4ff4ca9b753ca3f239e6fa0be005 /lib/lockref.c
parent32426f6653cbfde1ca16aff27a530ee36332f796 (diff)
dcache: let the dentry count go down to zero without taking d_lock
We can be more aggressive about this, if we are clever and careful. This is subtle. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'lib/lockref.c')
-rw-r--r--lib/lockref.c36
1 files changed, 28 insertions, 8 deletions
diff --git a/lib/lockref.c b/lib/lockref.c
index d2233de9a86e..ecb9a665ec19 100644
--- a/lib/lockref.c
+++ b/lib/lockref.c
@@ -60,7 +60,7 @@ void lockref_get(struct lockref *lockref)
EXPORT_SYMBOL(lockref_get);
/**
- * lockref_get_not_zero - Increments count unless the count is 0
+ * lockref_get_not_zero - Increments count unless the count is 0 or dead
* @lockref: pointer to lockref structure
* Return: 1 if count updated successfully or 0 if count was zero
*/
@@ -70,7 +70,7 @@ int lockref_get_not_zero(struct lockref *lockref)
CMPXCHG_LOOP(
new.count++;
- if (!old.count)
+ if (old.count <= 0)
return 0;
,
return 1;
@@ -78,7 +78,7 @@ int lockref_get_not_zero(struct lockref *lockref)
spin_lock(&lockref->lock);
retval = 0;
- if (lockref->count) {
+ if (lockref->count > 0) {
lockref->count++;
retval = 1;
}
@@ -88,7 +88,7 @@ int lockref_get_not_zero(struct lockref *lockref)
EXPORT_SYMBOL(lockref_get_not_zero);
/**
- * lockref_get_or_lock - Increments count unless the count is 0
+ * lockref_get_or_lock - Increments count unless the count is 0 or dead
* @lockref: pointer to lockref structure
* Return: 1 if count updated successfully or 0 if count was zero
* and we got the lock instead.
@@ -97,14 +97,14 @@ int lockref_get_or_lock(struct lockref *lockref)
{
CMPXCHG_LOOP(
new.count++;
- if (!old.count)
+ if (old.count <= 0)
break;
,
return 1;
);
spin_lock(&lockref->lock);
- if (!lockref->count)
+ if (lockref->count <= 0)
return 0;
lockref->count++;
spin_unlock(&lockref->lock);
@@ -113,6 +113,26 @@ int lockref_get_or_lock(struct lockref *lockref)
EXPORT_SYMBOL(lockref_get_or_lock);
/**
+ * lockref_put_return - Decrement reference count if possible
+ * @lockref: pointer to lockref structure
+ *
+ * Decrement the reference count and return the new value.
+ * If the lockref was dead or locked, return an error.
+ */
+int lockref_put_return(struct lockref *lockref)
+{
+ CMPXCHG_LOOP(
+ new.count--;
+ if (old.count <= 0)
+ return -1;
+ ,
+ return new.count;
+ );
+ return -1;
+}
+EXPORT_SYMBOL(lockref_put_return);
+
+/**
* lockref_put_or_lock - decrements count unless count <= 1 before decrement
* @lockref: pointer to lockref structure
* Return: 1 if count updated successfully or 0 if count <= 1 and lock taken
@@ -158,7 +178,7 @@ int lockref_get_not_dead(struct lockref *lockref)
CMPXCHG_LOOP(
new.count++;
- if ((int)old.count < 0)
+ if (old.count < 0)
return 0;
,
return 1;
@@ -166,7 +186,7 @@ int lockref_get_not_dead(struct lockref *lockref)
spin_lock(&lockref->lock);
retval = 0;
- if ((int) lockref->count >= 0) {
+ if (lockref->count >= 0) {
lockref->count++;
retval = 1;
}