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![NeilBrown](/assets/img/avatar_default.png)
commit d202cce896
sunrpc: never return expired entries in sunrpc_cache_lookup
moved the 'entry is expired' test from cache_check to
sunrpc_cache_lookup, so that it happened early and some races could
safely be ignored.
However the ip_map (in svcauth_unix.c) has a separate single-item
cache which allows quick lookup without locking. An entry in this
case would not be subject to the expiry test and so could be used
well after it has expired.
This is not normally a big problem because the first time it is used
after it is expired an up-call will be scheduled to refresh the entry
(if it hasn't been scheduled already) and the old entry will then
be invalidated. So on the second attempt to use it after it has
expired, ip_map_cached_get will discard it.
However that is subtle and not ideal, so replace the "!cache_valid"
test with "cache_is_expired".
In doing this we drop the test on the "CACHE_VALID" bit. This is
unnecessary as the bit is never cleared, and an entry will only
be cached if the bit is set.
Reported-by: Bodo Stroesser <bstroesser@ts.fujitsu.com>
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
280 lines
7.8 KiB
C
280 lines
7.8 KiB
C
/*
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* include/linux/sunrpc/cache.h
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*
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* Generic code for various authentication-related caches
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* used by sunrpc clients and servers.
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*
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* Copyright (C) 2002 Neil Brown <neilb@cse.unsw.edu.au>
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*
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* Released under terms in GPL version 2. See COPYING.
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*
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*/
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#ifndef _LINUX_SUNRPC_CACHE_H_
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#define _LINUX_SUNRPC_CACHE_H_
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#include <linux/kref.h>
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#include <linux/slab.h>
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#include <linux/atomic.h>
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#include <linux/proc_fs.h>
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/*
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* Each cache requires:
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* - A 'struct cache_detail' which contains information specific to the cache
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* for common code to use.
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* - An item structure that must contain a "struct cache_head"
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* - A lookup function defined using DefineCacheLookup
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* - A 'put' function that can release a cache item. It will only
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* be called after cache_put has succeed, so there are guarantee
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* to be no references.
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* - A function to calculate a hash of an item's key.
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*
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* as well as assorted code fragments (e.g. compare keys) and numbers
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* (e.g. hash size, goal_age, etc).
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*
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* Each cache must be registered so that it can be cleaned regularly.
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* When the cache is unregistered, it is flushed completely.
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*
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* Entries have a ref count and a 'hashed' flag which counts the existence
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* in the hash table.
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* We only expire entries when refcount is zero.
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* Existence in the cache is counted the refcount.
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*/
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/* Every cache item has a common header that is used
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* for expiring and refreshing entries.
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*
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*/
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struct cache_head {
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struct cache_head * next;
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time_t expiry_time; /* After time time, don't use the data */
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time_t last_refresh; /* If CACHE_PENDING, this is when upcall
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* was sent, else this is when update was received
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*/
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struct kref ref;
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unsigned long flags;
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};
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#define CACHE_VALID 0 /* Entry contains valid data */
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#define CACHE_NEGATIVE 1 /* Negative entry - there is no match for the key */
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#define CACHE_PENDING 2 /* An upcall has been sent but no reply received yet*/
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#define CACHE_CLEANED 3 /* Entry has been cleaned from cache */
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#define CACHE_NEW_EXPIRY 120 /* keep new things pending confirmation for 120 seconds */
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struct cache_detail_procfs {
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struct proc_dir_entry *proc_ent;
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struct proc_dir_entry *flush_ent, *channel_ent, *content_ent;
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};
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struct cache_detail_pipefs {
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struct dentry *dir;
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};
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struct cache_detail {
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struct module * owner;
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int hash_size;
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struct cache_head ** hash_table;
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rwlock_t hash_lock;
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atomic_t inuse; /* active user-space update or lookup */
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char *name;
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void (*cache_put)(struct kref *);
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int (*cache_upcall)(struct cache_detail *,
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struct cache_head *);
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void (*cache_request)(struct cache_detail *cd,
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struct cache_head *ch,
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char **bpp, int *blen);
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int (*cache_parse)(struct cache_detail *,
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char *buf, int len);
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int (*cache_show)(struct seq_file *m,
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struct cache_detail *cd,
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struct cache_head *h);
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void (*warn_no_listener)(struct cache_detail *cd,
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int has_died);
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struct cache_head * (*alloc)(void);
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int (*match)(struct cache_head *orig, struct cache_head *new);
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void (*init)(struct cache_head *orig, struct cache_head *new);
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void (*update)(struct cache_head *orig, struct cache_head *new);
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/* fields below this comment are for internal use
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* and should not be touched by cache owners
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*/
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time_t flush_time; /* flush all cache items with last_refresh
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* earlier than this */
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struct list_head others;
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time_t nextcheck;
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int entries;
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/* fields for communication over channel */
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struct list_head queue;
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atomic_t readers; /* how many time is /chennel open */
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time_t last_close; /* if no readers, when did last close */
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time_t last_warn; /* when we last warned about no readers */
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union {
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struct cache_detail_procfs procfs;
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struct cache_detail_pipefs pipefs;
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} u;
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struct net *net;
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};
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/* this must be embedded in any request structure that
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* identifies an object that will want a callback on
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* a cache fill
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*/
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struct cache_req {
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struct cache_deferred_req *(*defer)(struct cache_req *req);
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int thread_wait; /* How long (jiffies) we can block the
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* current thread to wait for updates.
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*/
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};
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/* this must be embedded in a deferred_request that is being
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* delayed awaiting cache-fill
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*/
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struct cache_deferred_req {
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struct hlist_node hash; /* on hash chain */
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struct list_head recent; /* on fifo */
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struct cache_head *item; /* cache item we wait on */
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void *owner; /* we might need to discard all defered requests
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* owned by someone */
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void (*revisit)(struct cache_deferred_req *req,
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int too_many);
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};
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/*
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* timestamps kept in the cache are expressed in seconds
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* since boot. This is the best for measuring differences in
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* real time.
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*/
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static inline time_t seconds_since_boot(void)
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{
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struct timespec boot;
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getboottime(&boot);
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return get_seconds() - boot.tv_sec;
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}
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static inline time_t convert_to_wallclock(time_t sinceboot)
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{
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struct timespec boot;
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getboottime(&boot);
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return boot.tv_sec + sinceboot;
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}
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extern const struct file_operations cache_file_operations_pipefs;
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extern const struct file_operations content_file_operations_pipefs;
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extern const struct file_operations cache_flush_operations_pipefs;
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extern struct cache_head *
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sunrpc_cache_lookup(struct cache_detail *detail,
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struct cache_head *key, int hash);
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extern struct cache_head *
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sunrpc_cache_update(struct cache_detail *detail,
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struct cache_head *new, struct cache_head *old, int hash);
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extern int
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sunrpc_cache_pipe_upcall(struct cache_detail *detail, struct cache_head *h);
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extern void cache_clean_deferred(void *owner);
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static inline struct cache_head *cache_get(struct cache_head *h)
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{
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kref_get(&h->ref);
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return h;
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}
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static inline void cache_put(struct cache_head *h, struct cache_detail *cd)
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{
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if (atomic_read(&h->ref.refcount) <= 2 &&
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h->expiry_time < cd->nextcheck)
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cd->nextcheck = h->expiry_time;
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kref_put(&h->ref, cd->cache_put);
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}
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static inline int cache_is_expired(struct cache_detail *detail, struct cache_head *h)
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{
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return (h->expiry_time < seconds_since_boot()) ||
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(detail->flush_time > h->last_refresh);
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}
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extern int cache_check(struct cache_detail *detail,
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struct cache_head *h, struct cache_req *rqstp);
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extern void cache_flush(void);
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extern void cache_purge(struct cache_detail *detail);
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#define NEVER (0x7FFFFFFF)
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extern void __init cache_initialize(void);
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extern int cache_register_net(struct cache_detail *cd, struct net *net);
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extern void cache_unregister_net(struct cache_detail *cd, struct net *net);
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extern struct cache_detail *cache_create_net(struct cache_detail *tmpl, struct net *net);
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extern void cache_destroy_net(struct cache_detail *cd, struct net *net);
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extern void sunrpc_init_cache_detail(struct cache_detail *cd);
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extern void sunrpc_destroy_cache_detail(struct cache_detail *cd);
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extern int sunrpc_cache_register_pipefs(struct dentry *parent, const char *,
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umode_t, struct cache_detail *);
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extern void sunrpc_cache_unregister_pipefs(struct cache_detail *);
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extern void qword_add(char **bpp, int *lp, char *str);
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extern void qword_addhex(char **bpp, int *lp, char *buf, int blen);
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extern int qword_get(char **bpp, char *dest, int bufsize);
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static inline int get_int(char **bpp, int *anint)
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{
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char buf[50];
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char *ep;
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int rv;
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int len = qword_get(bpp, buf, sizeof(buf));
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if (len < 0)
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return -EINVAL;
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if (len == 0)
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return -ENOENT;
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rv = simple_strtol(buf, &ep, 0);
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if (*ep)
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return -EINVAL;
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*anint = rv;
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return 0;
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}
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static inline int get_uint(char **bpp, unsigned int *anint)
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{
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char buf[50];
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int len = qword_get(bpp, buf, sizeof(buf));
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if (len < 0)
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return -EINVAL;
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if (len == 0)
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return -ENOENT;
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if (kstrtouint(buf, 0, anint))
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return -EINVAL;
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return 0;
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}
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static inline time_t get_expiry(char **bpp)
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{
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int rv;
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struct timespec boot;
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if (get_int(bpp, &rv))
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return 0;
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if (rv < 0)
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return 0;
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getboottime(&boot);
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return rv - boot.tv_sec;
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}
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#endif /* _LINUX_SUNRPC_CACHE_H_ */
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