![Jeff Layton](/assets/img/avatar_default.png)
If we end up doing "goto out_nomem" in this function, we'll call nfsd_reply_cache_shutdown. That will attempt to walk the LRU list and free entries, but that list may not be initialized yet if the server is starting up for the first time. It's also possible for the shrinker to kick in before we've initialized the LRU list. Rearrange the initialization so that the LRU list_head and cache size are initialized before doing any of the allocations that might fail. Signed-off-by: Jeff Layton <jlayton@redhat.com> Signed-off-by: J. Bruce Fields <bfields@redhat.com>
526 lines
13 KiB
C
526 lines
13 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 <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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#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 struct kmem_cache *drc_slab;
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static unsigned int num_drc_entries;
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static unsigned int max_drc_entries;
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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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static void cache_cleaner_func(struct work_struct *unused);
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static int nfsd_reply_cache_shrink(struct shrinker *shrink,
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struct shrink_control *sc);
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struct shrinker nfsd_reply_cache_shrinker = {
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.shrink = nfsd_reply_cache_shrink,
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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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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)
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kfree(rp->c_replvec.iov_base);
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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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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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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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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 + request_hash(rp->c_xid));
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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 void
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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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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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}
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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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}
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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 int
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nfsd_reply_cache_shrink(struct shrinker *shrink, struct shrink_control *sc)
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{
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unsigned int num;
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spin_lock(&cache_lock);
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if (sc->nr_to_scan)
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prune_cache_entries();
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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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/*
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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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/*
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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;
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struct hlist_head *rh;
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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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rh = &cache_hash[request_hash(xid)];
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hlist_for_each_entry(rp, rh, c_hash) {
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if (xid == rp->c_xid && proc == rp->c_proc &&
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proto == rp->c_prot && vers == rp->c_vers &&
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rqstp->rq_arg.len == rp->c_len && csum == rp->c_csum &&
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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 rp;
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}
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return NULL;
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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;
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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 RC_DOIT;
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}
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csum = nfsd_cache_csum(rqstp);
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spin_lock(&cache_lock);
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rtn = RC_DOIT;
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rp = nfsd_cache_search(rqstp, csum);
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if (rp)
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goto found_entry;
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/* Try to use the first entry on the LRU */
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if (!list_empty(&lru_head)) {
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rp = list_first_entry(&lru_head, struct svc_cacherep, 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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lru_put_end(rp);
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prune_cache_entries();
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goto setup_entry;
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}
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}
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/* Drop the lock and allocate a new entry */
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spin_unlock(&cache_lock);
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rp = nfsd_reply_cache_alloc();
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if (!rp) {
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dprintk("nfsd: unable to allocate DRC entry!\n");
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return RC_DOIT;
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}
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spin_lock(&cache_lock);
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++num_drc_entries;
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/*
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* Must search again just in case someone inserted one
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* after we dropped the lock above.
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*/
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found = nfsd_cache_search(rqstp, csum);
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if (found) {
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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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/*
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* We're keeping the one we just allocated. Are we now over the
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* limit? Prune one off the tip of the LRU in trade for the one we
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* just allocated if so.
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*/
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if (num_drc_entries >= max_drc_entries)
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nfsd_reply_cache_free_locked(list_first_entry(&lru_head,
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struct svc_cacherep, c_lru));
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setup_entry:
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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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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
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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 = rqstp->rq_cacherep;
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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)
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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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nfsd_reply_cache_free(rp);
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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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nfsd_reply_cache_free(rp);
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return;
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}
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cachv->iov_len = len << 2;
|
|
memcpy(cachv->iov_base, statp, len << 2);
|
|
break;
|
|
case RC_NOCACHE:
|
|
nfsd_reply_cache_free(rp);
|
|
return;
|
|
}
|
|
spin_lock(&cache_lock);
|
|
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;
|
|
}
|