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![J. Bruce Fields](/assets/img/avatar_default.png)
It's sort of ridiculous that we've never had a working reply cache for NFSv4. On the other hand, we may still not: our current reply cache is likely not very good, especially in the TCP case (which is the only case that matters for v4). What we really need here is some serious testing. Anyway, here's a start. Signed-off-by: J. Bruce Fields <bfields@redhat.com>
323 lines
7.6 KiB
C
323 lines
7.6 KiB
C
/*
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* Request reply cache. This is currently a global cache, but this may
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* change in the future and be a per-client cache.
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*
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* This code is heavily inspired by the 44BSD implementation, although
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* it does things a bit differently.
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*
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* Copyright (C) 1995, 1996 Olaf Kirch <okir@monad.swb.de>
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*/
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#include <linux/slab.h>
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#include "nfsd.h"
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#include "cache.h"
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/* Size of reply cache. Common values are:
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* 4.3BSD: 128
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* 4.4BSD: 256
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* Solaris2: 1024
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* DEC Unix: 512-4096
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*/
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#define CACHESIZE 1024
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#define HASHSIZE 64
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static struct hlist_head * cache_hash;
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static struct list_head lru_head;
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static int cache_disabled = 1;
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/*
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* Calculate the hash index from an XID.
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*/
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static inline u32 request_hash(u32 xid)
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{
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u32 h = xid;
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h ^= (xid >> 24);
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return h & (HASHSIZE-1);
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}
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static int nfsd_cache_append(struct svc_rqst *rqstp, struct kvec *vec);
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/*
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* locking for the reply cache:
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* A cache entry is "single use" if c_state == RC_INPROG
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* Otherwise, it when accessing _prev or _next, the lock must be held.
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*/
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static DEFINE_SPINLOCK(cache_lock);
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int nfsd_reply_cache_init(void)
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{
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struct svc_cacherep *rp;
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int i;
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INIT_LIST_HEAD(&lru_head);
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i = CACHESIZE;
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while (i) {
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rp = kmalloc(sizeof(*rp), GFP_KERNEL);
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if (!rp)
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goto out_nomem;
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list_add(&rp->c_lru, &lru_head);
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rp->c_state = RC_UNUSED;
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rp->c_type = RC_NOCACHE;
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INIT_HLIST_NODE(&rp->c_hash);
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i--;
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}
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cache_hash = kcalloc (HASHSIZE, sizeof(struct hlist_head), GFP_KERNEL);
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if (!cache_hash)
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goto out_nomem;
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cache_disabled = 0;
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return 0;
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out_nomem:
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printk(KERN_ERR "nfsd: failed to allocate reply cache\n");
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nfsd_reply_cache_shutdown();
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return -ENOMEM;
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}
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void nfsd_reply_cache_shutdown(void)
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{
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struct svc_cacherep *rp;
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while (!list_empty(&lru_head)) {
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rp = list_entry(lru_head.next, struct svc_cacherep, c_lru);
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if (rp->c_state == RC_DONE && rp->c_type == RC_REPLBUFF)
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kfree(rp->c_replvec.iov_base);
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list_del(&rp->c_lru);
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kfree(rp);
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}
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cache_disabled = 1;
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kfree (cache_hash);
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cache_hash = NULL;
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}
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/*
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* Move cache entry to end of LRU list
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*/
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static void
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lru_put_end(struct svc_cacherep *rp)
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{
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list_move_tail(&rp->c_lru, &lru_head);
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}
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/*
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* Move a cache entry from one hash list to another
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*/
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static void
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hash_refile(struct svc_cacherep *rp)
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{
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hlist_del_init(&rp->c_hash);
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hlist_add_head(&rp->c_hash, cache_hash + request_hash(rp->c_xid));
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}
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/*
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* Try to find an entry matching the current call in the cache. When none
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* is found, we grab the oldest unlocked entry off the LRU list.
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* Note that no operation within the loop may sleep.
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*/
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int
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nfsd_cache_lookup(struct svc_rqst *rqstp)
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{
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struct hlist_node *hn;
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struct hlist_head *rh;
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struct svc_cacherep *rp;
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__be32 xid = rqstp->rq_xid;
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u32 proto = rqstp->rq_prot,
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vers = rqstp->rq_vers,
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proc = rqstp->rq_proc;
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unsigned long age;
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int type = rqstp->rq_cachetype;
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int rtn;
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rqstp->rq_cacherep = NULL;
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if (cache_disabled || type == RC_NOCACHE) {
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nfsdstats.rcnocache++;
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return RC_DOIT;
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}
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spin_lock(&cache_lock);
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rtn = RC_DOIT;
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rh = &cache_hash[request_hash(xid)];
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hlist_for_each_entry(rp, hn, rh, c_hash) {
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if (rp->c_state != RC_UNUSED &&
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xid == rp->c_xid && proc == rp->c_proc &&
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proto == rp->c_prot && vers == rp->c_vers &&
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time_before(jiffies, rp->c_timestamp + 120*HZ) &&
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memcmp((char*)&rqstp->rq_addr, (char*)&rp->c_addr, sizeof(rp->c_addr))==0) {
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nfsdstats.rchits++;
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goto found_entry;
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}
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}
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nfsdstats.rcmisses++;
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/* This loop shouldn't take more than a few iterations normally */
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{
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int safe = 0;
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list_for_each_entry(rp, &lru_head, c_lru) {
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if (rp->c_state != RC_INPROG)
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break;
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if (safe++ > CACHESIZE) {
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printk("nfsd: loop in repcache LRU list\n");
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cache_disabled = 1;
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goto out;
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}
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}
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}
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/* All entries on the LRU are in-progress. This should not happen */
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if (&rp->c_lru == &lru_head) {
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static int complaints;
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printk(KERN_WARNING "nfsd: all repcache entries locked!\n");
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if (++complaints > 5) {
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printk(KERN_WARNING "nfsd: disabling repcache.\n");
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cache_disabled = 1;
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}
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goto out;
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}
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rqstp->rq_cacherep = rp;
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rp->c_state = RC_INPROG;
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rp->c_xid = xid;
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rp->c_proc = proc;
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memcpy(&rp->c_addr, svc_addr_in(rqstp), sizeof(rp->c_addr));
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rp->c_prot = proto;
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rp->c_vers = vers;
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rp->c_timestamp = jiffies;
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hash_refile(rp);
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/* release any buffer */
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if (rp->c_type == RC_REPLBUFF) {
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kfree(rp->c_replvec.iov_base);
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rp->c_replvec.iov_base = NULL;
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}
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rp->c_type = RC_NOCACHE;
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out:
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spin_unlock(&cache_lock);
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return rtn;
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found_entry:
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/* We found a matching entry which is either in progress or done. */
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age = jiffies - rp->c_timestamp;
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rp->c_timestamp = jiffies;
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lru_put_end(rp);
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rtn = RC_DROPIT;
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/* Request being processed or excessive rexmits */
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if (rp->c_state == RC_INPROG || age < RC_DELAY)
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goto out;
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/* From the hall of fame of impractical attacks:
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* Is this a user who tries to snoop on the cache? */
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rtn = RC_DOIT;
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if (!rqstp->rq_secure && rp->c_secure)
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goto out;
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/* Compose RPC reply header */
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switch (rp->c_type) {
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case RC_NOCACHE:
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break;
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case RC_REPLSTAT:
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svc_putu32(&rqstp->rq_res.head[0], rp->c_replstat);
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rtn = RC_REPLY;
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break;
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case RC_REPLBUFF:
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if (!nfsd_cache_append(rqstp, &rp->c_replvec))
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goto out; /* should not happen */
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rtn = RC_REPLY;
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break;
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default:
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printk(KERN_WARNING "nfsd: bad repcache type %d\n", rp->c_type);
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rp->c_state = RC_UNUSED;
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}
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goto out;
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}
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/*
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* Update a cache entry. This is called from nfsd_dispatch when
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* the procedure has been executed and the complete reply is in
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* rqstp->rq_res.
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*
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* We're copying around data here rather than swapping buffers because
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* the toplevel loop requires max-sized buffers, which would be a waste
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* of memory for a cache with a max reply size of 100 bytes (diropokres).
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*
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* If we should start to use different types of cache entries tailored
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* specifically for attrstat and fh's, we may save even more space.
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*
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* Also note that a cachetype of RC_NOCACHE can legally be passed when
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* nfsd failed to encode a reply that otherwise would have been cached.
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* In this case, nfsd_cache_update is called with statp == NULL.
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*/
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void
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nfsd_cache_update(struct svc_rqst *rqstp, int cachetype, __be32 *statp)
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{
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struct svc_cacherep *rp;
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struct kvec *resv = &rqstp->rq_res.head[0], *cachv;
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int len;
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if (!(rp = rqstp->rq_cacherep) || cache_disabled)
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return;
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len = resv->iov_len - ((char*)statp - (char*)resv->iov_base);
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len >>= 2;
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/* Don't cache excessive amounts of data and XDR failures */
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if (!statp || len > (256 >> 2)) {
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rp->c_state = RC_UNUSED;
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return;
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}
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switch (cachetype) {
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case RC_REPLSTAT:
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if (len != 1)
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printk("nfsd: RC_REPLSTAT/reply len %d!\n",len);
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rp->c_replstat = *statp;
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break;
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case RC_REPLBUFF:
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cachv = &rp->c_replvec;
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cachv->iov_base = kmalloc(len << 2, GFP_KERNEL);
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if (!cachv->iov_base) {
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spin_lock(&cache_lock);
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rp->c_state = RC_UNUSED;
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spin_unlock(&cache_lock);
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return;
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}
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cachv->iov_len = len << 2;
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memcpy(cachv->iov_base, statp, len << 2);
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break;
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}
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spin_lock(&cache_lock);
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lru_put_end(rp);
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rp->c_secure = rqstp->rq_secure;
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rp->c_type = cachetype;
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rp->c_state = RC_DONE;
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rp->c_timestamp = jiffies;
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spin_unlock(&cache_lock);
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return;
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}
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/*
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* Copy cached reply to current reply buffer. Should always fit.
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* FIXME as reply is in a page, we should just attach the page, and
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* keep a refcount....
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*/
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static int
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nfsd_cache_append(struct svc_rqst *rqstp, struct kvec *data)
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{
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struct kvec *vec = &rqstp->rq_res.head[0];
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if (vec->iov_len + data->iov_len > PAGE_SIZE) {
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printk(KERN_WARNING "nfsd: cached reply too large (%Zd).\n",
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data->iov_len);
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return 0;
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}
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memcpy((char*)vec->iov_base + vec->iov_len, data->iov_base, data->iov_len);
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vec->iov_len += data->iov_len;
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return 1;
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}
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