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dcache: let the dentry count go down to zero without taking d_lock

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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>
This commit is contained in:
Linus Torvalds
2015-01-09 15:19:03 -08:00
committed by Al Viro
parent 32426f6653
commit 360f54796e
3 changed files with 144 additions and 13 deletions
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36
lib/lockref.c
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@@ -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);
@@ -112,6 +112,26 @@ 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
@@ -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;
}