0216bfcffe
The percpu counter data type are changed in this set of patches to support more users like ext3 who need more than 32 bit to store the free blocks total in the filesystem. - Generic perpcu counters data type changes. The size of the global counter and local counter were explictly specified using s64 and s32. The global counter is changed from long to s64, while the local counter is changed from long to s32, so we could avoid doing 64 bit update in most cases. - Users of the percpu counters are updated to make use of the new percpu_counter_init() routine now taking an additional parameter to allow users to pass the initial value of the global counter. Signed-off-by: Mingming Cao <cmm@us.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
114 lines
2.2 KiB
C
114 lines
2.2 KiB
C
#ifndef _LINUX_PERCPU_COUNTER_H
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#define _LINUX_PERCPU_COUNTER_H
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/*
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* A simple "approximate counter" for use in ext2 and ext3 superblocks.
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*
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* WARNING: these things are HUGE. 4 kbytes per counter on 32-way P4.
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*/
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#include <linux/spinlock.h>
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#include <linux/smp.h>
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#include <linux/threads.h>
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#include <linux/percpu.h>
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#include <linux/types.h>
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#ifdef CONFIG_SMP
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struct percpu_counter {
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spinlock_t lock;
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s64 count;
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s32 *counters;
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};
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#if NR_CPUS >= 16
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#define FBC_BATCH (NR_CPUS*2)
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#else
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#define FBC_BATCH (NR_CPUS*4)
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#endif
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static inline void percpu_counter_init(struct percpu_counter *fbc, s64 amount)
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{
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spin_lock_init(&fbc->lock);
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fbc->count = amount;
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fbc->counters = alloc_percpu(s32);
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}
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static inline void percpu_counter_destroy(struct percpu_counter *fbc)
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{
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free_percpu(fbc->counters);
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}
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void percpu_counter_mod(struct percpu_counter *fbc, s32 amount);
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s64 percpu_counter_sum(struct percpu_counter *fbc);
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static inline s64 percpu_counter_read(struct percpu_counter *fbc)
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{
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return fbc->count;
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}
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/*
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* It is possible for the percpu_counter_read() to return a small negative
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* number for some counter which should never be negative.
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*
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*/
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static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
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{
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s64 ret = fbc->count;
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barrier(); /* Prevent reloads of fbc->count */
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if (ret >= 0)
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return ret;
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return 1;
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}
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#else
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struct percpu_counter {
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s64 count;
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};
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static inline void percpu_counter_init(struct percpu_counter *fbc, s64 amount)
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{
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fbc->count = amount;
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}
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static inline void percpu_counter_destroy(struct percpu_counter *fbc)
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{
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}
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static inline void
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percpu_counter_mod(struct percpu_counter *fbc, s32 amount)
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{
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preempt_disable();
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fbc->count += amount;
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preempt_enable();
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}
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static inline s64 percpu_counter_read(struct percpu_counter *fbc)
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{
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return fbc->count;
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}
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static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
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{
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return fbc->count;
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}
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static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
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{
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return percpu_counter_read_positive(fbc);
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}
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#endif /* CONFIG_SMP */
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static inline void percpu_counter_inc(struct percpu_counter *fbc)
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{
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percpu_counter_mod(fbc, 1);
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}
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static inline void percpu_counter_dec(struct percpu_counter *fbc)
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{
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percpu_counter_mod(fbc, -1);
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}
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#endif /* _LINUX_PERCPU_COUNTER_H */
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