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e66cf16109
Currently glocks have an atomic reference count and also a spinlock which covers various internal fields, such as the state. This intent of this patch is to replace the spinlock and the atomic reference count with a lockref structure. This contains a spinlock which we can continue to use as before, and a reference counter which is used in conjuction with the spinlock to replace the previous atomic counter. As a result of this there are some new rules for reference counting on glocks. We need to distinguish between reference count changes under gl_spin (which are now just increment or decrement of the new counter, provided the count cannot hit zero) and those which are outside of gl_spin, but which now take gl_spin internally. The conversion is relatively straight forward. There is probably some further clean up which can be done, but the priority at this stage is to make the change in as simple a manner as possible. A consequence of this change is that the reference count is being decoupled from the lru list processing. This should allow future adoption of the lru_list code with glocks in due course. The reason for using the "dead" state and not just relying on 0 being the "invalid state" is so that in due course 0 ref counts can be allowable. The intent is to eventually be able to remove the ref count changes which are currently hidden away in state_change(). Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
46 lines
1.2 KiB
C
46 lines
1.2 KiB
C
#ifndef __LINUX_LOCKREF_H
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#define __LINUX_LOCKREF_H
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/*
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* Locked reference counts.
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*
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* These are different from just plain atomic refcounts in that they
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* are atomic with respect to the spinlock that goes with them. In
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* particular, there can be implementations that don't actually get
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* the spinlock for the common decrement/increment operations, but they
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* still have to check that the operation is done semantically as if
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* the spinlock had been taken (using a cmpxchg operation that covers
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* both the lock and the count word, or using memory transactions, for
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* example).
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*/
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#include <linux/spinlock.h>
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struct lockref {
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union {
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#ifdef CONFIG_CMPXCHG_LOCKREF
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aligned_u64 lock_count;
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#endif
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struct {
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spinlock_t lock;
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unsigned int count;
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};
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};
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};
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extern void lockref_get(struct lockref *);
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extern int lockref_get_not_zero(struct lockref *);
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extern int lockref_get_or_lock(struct lockref *);
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extern int lockref_put_or_lock(struct lockref *);
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extern void lockref_mark_dead(struct lockref *);
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extern int lockref_get_not_dead(struct lockref *);
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/* Must be called under spinlock for reliable results */
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static inline int __lockref_is_dead(const struct lockref *l)
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{
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return ((int)l->count < 0);
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}
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#endif /* __LINUX_LOCKREF_H */
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