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![Jeff Layton](/assets/img/avatar_default.png)
Currently when we are processing a request, we try to scrape an expired or over-limit entry off the list in preference to allocating a new one from the slab. This is unnecessarily complicated. Just use the slab layer. Signed-off-by: Jeff Layton <jlayton@redhat.com> Signed-off-by: J. Bruce Fields <bfields@redhat.com>
613 lines
16 KiB
C
613 lines
16 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 <linux/sunrpc/addr.h>
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#include <linux/highmem.h>
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#include <linux/log2.h>
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#include <linux/hash.h>
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#include <net/checksum.h>
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#include "nfsd.h"
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#include "cache.h"
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#define NFSDDBG_FACILITY NFSDDBG_REPCACHE
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/*
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* We use this value to determine the number of hash buckets from the max
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* cache size, the idea being that when the cache is at its maximum number
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* of entries, then this should be the average number of entries per bucket.
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*/
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#define TARGET_BUCKET_SIZE 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 struct kmem_cache *drc_slab;
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/* max number of entries allowed in the cache */
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static unsigned int max_drc_entries;
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/* number of significant bits in the hash value */
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static unsigned int maskbits;
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/*
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* Stats and other tracking of on the duplicate reply cache. All of these and
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* the "rc" fields in nfsdstats are protected by the cache_lock
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*/
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/* total number of entries */
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static unsigned int num_drc_entries;
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/* cache misses due only to checksum comparison failures */
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static unsigned int payload_misses;
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/* amount of memory (in bytes) currently consumed by the DRC */
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static unsigned int drc_mem_usage;
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/* longest hash chain seen */
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static unsigned int longest_chain;
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/* size of cache when we saw the longest hash chain */
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static unsigned int longest_chain_cachesize;
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static int nfsd_cache_append(struct svc_rqst *rqstp, struct kvec *vec);
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static void cache_cleaner_func(struct work_struct *unused);
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static unsigned long nfsd_reply_cache_count(struct shrinker *shrink,
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struct shrink_control *sc);
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static unsigned long nfsd_reply_cache_scan(struct shrinker *shrink,
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struct shrink_control *sc);
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static struct shrinker nfsd_reply_cache_shrinker = {
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.scan_objects = nfsd_reply_cache_scan,
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.count_objects = nfsd_reply_cache_count,
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.seeks = 1,
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};
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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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static DECLARE_DELAYED_WORK(cache_cleaner, cache_cleaner_func);
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/*
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* Put a cap on the size of the DRC based on the amount of available
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* low memory in the machine.
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*
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* 64MB: 8192
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* 128MB: 11585
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* 256MB: 16384
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* 512MB: 23170
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* 1GB: 32768
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* 2GB: 46340
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* 4GB: 65536
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* 8GB: 92681
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* 16GB: 131072
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*
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* ...with a hard cap of 256k entries. In the worst case, each entry will be
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* ~1k, so the above numbers should give a rough max of the amount of memory
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* used in k.
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*/
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static unsigned int
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nfsd_cache_size_limit(void)
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{
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unsigned int limit;
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unsigned long low_pages = totalram_pages - totalhigh_pages;
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limit = (16 * int_sqrt(low_pages)) << (PAGE_SHIFT-10);
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return min_t(unsigned int, limit, 256*1024);
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}
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/*
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* Compute the number of hash buckets we need. Divide the max cachesize by
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* the "target" max bucket size, and round up to next power of two.
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*/
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static unsigned int
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nfsd_hashsize(unsigned int limit)
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{
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return roundup_pow_of_two(limit / TARGET_BUCKET_SIZE);
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}
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static struct svc_cacherep *
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nfsd_reply_cache_alloc(void)
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{
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struct svc_cacherep *rp;
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rp = kmem_cache_alloc(drc_slab, GFP_KERNEL);
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if (rp) {
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rp->c_state = RC_UNUSED;
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rp->c_type = RC_NOCACHE;
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INIT_LIST_HEAD(&rp->c_lru);
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INIT_HLIST_NODE(&rp->c_hash);
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}
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return rp;
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}
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static void
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nfsd_reply_cache_free_locked(struct svc_cacherep *rp)
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{
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if (rp->c_type == RC_REPLBUFF && rp->c_replvec.iov_base) {
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drc_mem_usage -= rp->c_replvec.iov_len;
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kfree(rp->c_replvec.iov_base);
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}
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if (!hlist_unhashed(&rp->c_hash))
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hlist_del(&rp->c_hash);
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list_del(&rp->c_lru);
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--num_drc_entries;
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drc_mem_usage -= sizeof(*rp);
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kmem_cache_free(drc_slab, rp);
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}
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static void
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nfsd_reply_cache_free(struct svc_cacherep *rp)
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{
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spin_lock(&cache_lock);
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nfsd_reply_cache_free_locked(rp);
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spin_unlock(&cache_lock);
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}
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int nfsd_reply_cache_init(void)
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{
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unsigned int hashsize;
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INIT_LIST_HEAD(&lru_head);
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max_drc_entries = nfsd_cache_size_limit();
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num_drc_entries = 0;
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hashsize = nfsd_hashsize(max_drc_entries);
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maskbits = ilog2(hashsize);
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register_shrinker(&nfsd_reply_cache_shrinker);
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drc_slab = kmem_cache_create("nfsd_drc", sizeof(struct svc_cacherep),
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0, 0, NULL);
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if (!drc_slab)
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goto out_nomem;
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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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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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unregister_shrinker(&nfsd_reply_cache_shrinker);
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cancel_delayed_work_sync(&cache_cleaner);
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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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nfsd_reply_cache_free_locked(rp);
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}
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kfree (cache_hash);
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cache_hash = NULL;
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if (drc_slab) {
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kmem_cache_destroy(drc_slab);
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drc_slab = NULL;
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}
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}
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/*
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* Move cache entry to end of LRU list, and queue the cleaner to run if it's
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* not already scheduled.
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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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rp->c_timestamp = jiffies;
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list_move_tail(&rp->c_lru, &lru_head);
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schedule_delayed_work(&cache_cleaner, RC_EXPIRE);
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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 + hash_32(rp->c_xid, maskbits));
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}
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static inline bool
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nfsd_cache_entry_expired(struct svc_cacherep *rp)
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{
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return rp->c_state != RC_INPROG &&
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time_after(jiffies, rp->c_timestamp + RC_EXPIRE);
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}
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/*
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* Walk the LRU list and prune off entries that are older than RC_EXPIRE.
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* Also prune the oldest ones when the total exceeds the max number of entries.
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*/
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static long
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prune_cache_entries(void)
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{
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struct svc_cacherep *rp, *tmp;
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long freed = 0;
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list_for_each_entry_safe(rp, tmp, &lru_head, c_lru) {
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if (!nfsd_cache_entry_expired(rp) &&
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num_drc_entries <= max_drc_entries)
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break;
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nfsd_reply_cache_free_locked(rp);
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freed++;
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}
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/*
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* Conditionally rearm the job. If we cleaned out the list, then
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* cancel any pending run (since there won't be any work to do).
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* Otherwise, we rearm the job or modify the existing one to run in
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* RC_EXPIRE since we just ran the pruner.
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*/
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if (list_empty(&lru_head))
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cancel_delayed_work(&cache_cleaner);
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else
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mod_delayed_work(system_wq, &cache_cleaner, RC_EXPIRE);
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return freed;
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}
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static void
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cache_cleaner_func(struct work_struct *unused)
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{
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spin_lock(&cache_lock);
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prune_cache_entries();
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spin_unlock(&cache_lock);
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}
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static unsigned long
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nfsd_reply_cache_count(struct shrinker *shrink, struct shrink_control *sc)
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{
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unsigned long num;
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spin_lock(&cache_lock);
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num = num_drc_entries;
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spin_unlock(&cache_lock);
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return num;
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}
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static unsigned long
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nfsd_reply_cache_scan(struct shrinker *shrink, struct shrink_control *sc)
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{
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unsigned long freed;
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spin_lock(&cache_lock);
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freed = prune_cache_entries();
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spin_unlock(&cache_lock);
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return freed;
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}
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/*
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* Walk an xdr_buf and get a CRC for at most the first RC_CSUMLEN bytes
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*/
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static __wsum
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nfsd_cache_csum(struct svc_rqst *rqstp)
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{
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int idx;
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unsigned int base;
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__wsum csum;
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struct xdr_buf *buf = &rqstp->rq_arg;
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const unsigned char *p = buf->head[0].iov_base;
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size_t csum_len = min_t(size_t, buf->head[0].iov_len + buf->page_len,
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RC_CSUMLEN);
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size_t len = min(buf->head[0].iov_len, csum_len);
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/* rq_arg.head first */
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csum = csum_partial(p, len, 0);
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csum_len -= len;
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/* Continue into page array */
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idx = buf->page_base / PAGE_SIZE;
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base = buf->page_base & ~PAGE_MASK;
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while (csum_len) {
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p = page_address(buf->pages[idx]) + base;
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len = min_t(size_t, PAGE_SIZE - base, csum_len);
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csum = csum_partial(p, len, csum);
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csum_len -= len;
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base = 0;
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++idx;
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}
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return csum;
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}
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static bool
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nfsd_cache_match(struct svc_rqst *rqstp, __wsum csum, struct svc_cacherep *rp)
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{
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/* Check RPC header info first */
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if (rqstp->rq_xid != rp->c_xid || rqstp->rq_proc != rp->c_proc ||
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rqstp->rq_prot != rp->c_prot || rqstp->rq_vers != rp->c_vers ||
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rqstp->rq_arg.len != rp->c_len ||
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!rpc_cmp_addr(svc_addr(rqstp), (struct sockaddr *)&rp->c_addr) ||
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rpc_get_port(svc_addr(rqstp)) != rpc_get_port((struct sockaddr *)&rp->c_addr))
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return false;
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/* compare checksum of NFS data */
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if (csum != rp->c_csum) {
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++payload_misses;
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return false;
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}
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return true;
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}
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/*
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* Search the request hash for an entry that matches the given rqstp.
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* Must be called with cache_lock held. Returns the found entry or
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* NULL on failure.
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*/
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static struct svc_cacherep *
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nfsd_cache_search(struct svc_rqst *rqstp, __wsum csum)
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{
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struct svc_cacherep *rp, *ret = NULL;
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struct hlist_head *rh;
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unsigned int entries = 0;
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rh = &cache_hash[hash_32(rqstp->rq_xid, maskbits)];
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hlist_for_each_entry(rp, rh, c_hash) {
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++entries;
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if (nfsd_cache_match(rqstp, csum, rp)) {
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ret = rp;
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break;
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}
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}
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/* tally hash chain length stats */
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if (entries > longest_chain) {
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longest_chain = entries;
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longest_chain_cachesize = num_drc_entries;
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} else if (entries == longest_chain) {
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/* prefer to keep the smallest cachesize possible here */
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longest_chain_cachesize = min(longest_chain_cachesize,
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num_drc_entries);
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}
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return ret;
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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 try to grab the oldest expired entry off the LRU list. If
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* a suitable one isn't there, then drop the cache_lock and allocate a
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* new one, then search again in case one got inserted while this thread
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* didn't hold the lock.
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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 svc_cacherep *rp, *found;
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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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__wsum csum;
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unsigned long age;
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int type = rqstp->rq_cachetype;
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int rtn = RC_DOIT;
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rqstp->rq_cacherep = NULL;
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if (type == RC_NOCACHE) {
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nfsdstats.rcnocache++;
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return rtn;
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}
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csum = nfsd_cache_csum(rqstp);
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/*
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* Since the common case is a cache miss followed by an insert,
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* preallocate an entry.
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*/
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rp = nfsd_reply_cache_alloc();
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spin_lock(&cache_lock);
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if (likely(rp)) {
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++num_drc_entries;
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drc_mem_usage += sizeof(*rp);
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}
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/* go ahead and prune the cache */
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prune_cache_entries();
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found = nfsd_cache_search(rqstp, csum);
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if (found) {
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if (likely(rp))
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nfsd_reply_cache_free_locked(rp);
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rp = found;
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goto found_entry;
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}
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if (!rp) {
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dprintk("nfsd: unable to allocate DRC entry!\n");
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goto out;
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}
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nfsdstats.rcmisses++;
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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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rpc_copy_addr((struct sockaddr *)&rp->c_addr, svc_addr(rqstp));
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rpc_set_port((struct sockaddr *)&rp->c_addr, rpc_get_port(svc_addr(rqstp)));
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rp->c_prot = proto;
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rp->c_vers = vers;
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rp->c_len = rqstp->rq_arg.len;
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rp->c_csum = csum;
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hash_refile(rp);
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lru_put_end(rp);
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/* release any buffer */
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if (rp->c_type == RC_REPLBUFF) {
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drc_mem_usage -= rp->c_replvec.iov_len;
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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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nfsdstats.rchits++;
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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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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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nfsd_reply_cache_free_locked(rp);
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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
|
|
* the procedure has been executed and the complete reply is in
|
|
* rqstp->rq_res.
|
|
*
|
|
* We're copying around data here rather than swapping buffers because
|
|
* the toplevel loop requires max-sized buffers, which would be a waste
|
|
* of memory for a cache with a max reply size of 100 bytes (diropokres).
|
|
*
|
|
* If we should start to use different types of cache entries tailored
|
|
* specifically for attrstat and fh's, we may save even more space.
|
|
*
|
|
* Also note that a cachetype of RC_NOCACHE can legally be passed when
|
|
* nfsd failed to encode a reply that otherwise would have been cached.
|
|
* In this case, nfsd_cache_update is called with statp == NULL.
|
|
*/
|
|
void
|
|
nfsd_cache_update(struct svc_rqst *rqstp, int cachetype, __be32 *statp)
|
|
{
|
|
struct svc_cacherep *rp = rqstp->rq_cacherep;
|
|
struct kvec *resv = &rqstp->rq_res.head[0], *cachv;
|
|
int len;
|
|
size_t bufsize = 0;
|
|
|
|
if (!rp)
|
|
return;
|
|
|
|
len = resv->iov_len - ((char*)statp - (char*)resv->iov_base);
|
|
len >>= 2;
|
|
|
|
/* Don't cache excessive amounts of data and XDR failures */
|
|
if (!statp || len > (256 >> 2)) {
|
|
nfsd_reply_cache_free(rp);
|
|
return;
|
|
}
|
|
|
|
switch (cachetype) {
|
|
case RC_REPLSTAT:
|
|
if (len != 1)
|
|
printk("nfsd: RC_REPLSTAT/reply len %d!\n",len);
|
|
rp->c_replstat = *statp;
|
|
break;
|
|
case RC_REPLBUFF:
|
|
cachv = &rp->c_replvec;
|
|
bufsize = len << 2;
|
|
cachv->iov_base = kmalloc(bufsize, GFP_KERNEL);
|
|
if (!cachv->iov_base) {
|
|
nfsd_reply_cache_free(rp);
|
|
return;
|
|
}
|
|
cachv->iov_len = bufsize;
|
|
memcpy(cachv->iov_base, statp, bufsize);
|
|
break;
|
|
case RC_NOCACHE:
|
|
nfsd_reply_cache_free(rp);
|
|
return;
|
|
}
|
|
spin_lock(&cache_lock);
|
|
drc_mem_usage += bufsize;
|
|
lru_put_end(rp);
|
|
rp->c_secure = rqstp->rq_secure;
|
|
rp->c_type = cachetype;
|
|
rp->c_state = RC_DONE;
|
|
spin_unlock(&cache_lock);
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* Copy cached reply to current reply buffer. Should always fit.
|
|
* FIXME as reply is in a page, we should just attach the page, and
|
|
* keep a refcount....
|
|
*/
|
|
static int
|
|
nfsd_cache_append(struct svc_rqst *rqstp, struct kvec *data)
|
|
{
|
|
struct kvec *vec = &rqstp->rq_res.head[0];
|
|
|
|
if (vec->iov_len + data->iov_len > PAGE_SIZE) {
|
|
printk(KERN_WARNING "nfsd: cached reply too large (%Zd).\n",
|
|
data->iov_len);
|
|
return 0;
|
|
}
|
|
memcpy((char*)vec->iov_base + vec->iov_len, data->iov_base, data->iov_len);
|
|
vec->iov_len += data->iov_len;
|
|
return 1;
|
|
}
|
|
|
|
/*
|
|
* Note that fields may be added, removed or reordered in the future. Programs
|
|
* scraping this file for info should test the labels to ensure they're
|
|
* getting the correct field.
|
|
*/
|
|
static int nfsd_reply_cache_stats_show(struct seq_file *m, void *v)
|
|
{
|
|
spin_lock(&cache_lock);
|
|
seq_printf(m, "max entries: %u\n", max_drc_entries);
|
|
seq_printf(m, "num entries: %u\n", num_drc_entries);
|
|
seq_printf(m, "hash buckets: %u\n", 1 << maskbits);
|
|
seq_printf(m, "mem usage: %u\n", drc_mem_usage);
|
|
seq_printf(m, "cache hits: %u\n", nfsdstats.rchits);
|
|
seq_printf(m, "cache misses: %u\n", nfsdstats.rcmisses);
|
|
seq_printf(m, "not cached: %u\n", nfsdstats.rcnocache);
|
|
seq_printf(m, "payload misses: %u\n", payload_misses);
|
|
seq_printf(m, "longest chain len: %u\n", longest_chain);
|
|
seq_printf(m, "cachesize at longest: %u\n", longest_chain_cachesize);
|
|
spin_unlock(&cache_lock);
|
|
return 0;
|
|
}
|
|
|
|
int nfsd_reply_cache_stats_open(struct inode *inode, struct file *file)
|
|
{
|
|
return single_open(file, nfsd_reply_cache_stats_show, NULL);
|
|
}
|