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Commit aca8a23d authored by Jeff Layton's avatar Jeff Layton Committed by J. Bruce Fields
Browse files

nfsd: add recurring workqueue job to clean the cache 



It's not sufficient to only clean the cache when requests come in. What
if we have a flurry of activity and then the server goes idle? Add a
workqueue job that will clean the cache every RC_EXPIRE period.

Care is taken to only run this when we expect to have entries expiring.

Signed-off-by: default avatarJeff Layton <jlayton@redhat.com>
Signed-off-by: default avatarJ. Bruce Fields <bfields@redhat.com>
parent 2c6b691c

fs/nfsd/nfscache.c

+47 −3
Original line number Diff line number Diff line
@@ -36,6 +36,7 @@ static inline u32 request_hash(u32 xid) 
}



static int	nfsd_cache_append(struct svc_rqst *rqstp, struct kvec *vec);

static void	cache_cleaner_func(struct work_struct *unused);



/*

 * locking for the reply cache:
@@ -43,6 +44,7 @@ static int nfsd_cache_append(struct svc_rqst *rqstp, struct kvec *vec); 
 * Otherwise, it when accessing _prev or _next, the lock must be held.

 */

static DEFINE_SPINLOCK(cache_lock);

static DECLARE_DELAYED_WORK(cache_cleaner, cache_cleaner_func);



/*

 * Put a cap on the size of the DRC based on the amount of available
@@ -131,6 +133,8 @@ void nfsd_reply_cache_shutdown(void) 
{

	struct svc_cacherep	*rp;



	cancel_delayed_work_sync(&cache_cleaner);



	while (!list_empty(&lru_head)) {

		rp = list_entry(lru_head.next, struct svc_cacherep, c_lru);

		nfsd_reply_cache_free_locked(rp);
@@ -146,13 +150,15 @@ void nfsd_reply_cache_shutdown(void) 
}



/*

 * Move cache entry to end of LRU list

 * Move cache entry to end of LRU list, and queue the cleaner to run if it's

 * not already scheduled.

 */

static void

lru_put_end(struct svc_cacherep *rp)

{

	rp->c_timestamp = jiffies;

	list_move_tail(&rp->c_lru, &lru_head);

	schedule_delayed_work(&cache_cleaner, RC_EXPIRE);

}



/*
@@ -172,6 +178,42 @@ nfsd_cache_entry_expired(struct svc_cacherep *rp) 
	       time_after(jiffies, rp->c_timestamp + RC_EXPIRE);

}



/*

 * Walk the LRU list and prune off entries that are older than RC_EXPIRE.

 * Also prune the oldest ones when the total exceeds the max number of entries.

 */

static void

prune_cache_entries(void)

{

	struct svc_cacherep *rp, *tmp;



	list_for_each_entry_safe(rp, tmp, &lru_head, c_lru) {

		if (!nfsd_cache_entry_expired(rp) &&

		    num_drc_entries <= max_drc_entries)

			break;

		nfsd_reply_cache_free_locked(rp);

	}



	/*

	 * Conditionally rearm the job. If we cleaned out the list, then

	 * cancel any pending run (since there won't be any work to do).

	 * Otherwise, we rearm the job or modify the existing one to run in

	 * RC_EXPIRE since we just ran the pruner.

	 */

	if (list_empty(&lru_head))

		cancel_delayed_work(&cache_cleaner);

	else

		mod_delayed_work(system_wq, &cache_cleaner, RC_EXPIRE);

}



static void

cache_cleaner_func(struct work_struct *unused)

{

	spin_lock(&cache_lock);

	prune_cache_entries();

	spin_unlock(&cache_lock);

}



/*

 * Search the request hash for an entry that matches the given rqstp.

 * Must be called with cache_lock held. Returns the found entry or
@@ -192,7 +234,6 @@ nfsd_cache_search(struct svc_rqst *rqstp) 
	hlist_for_each_entry(rp, hn, rh, c_hash) {

		if (xid == rp->c_xid && proc == rp->c_proc &&

		    proto == rp->c_prot && vers == rp->c_vers &&

		    !nfsd_cache_entry_expired(rp) &&

		    rpc_cmp_addr(svc_addr(rqstp), (struct sockaddr *)&rp->c_addr) &&

		    rpc_get_port(svc_addr(rqstp)) == rpc_get_port((struct sockaddr *)&rp->c_addr))

			return rp;
@@ -234,9 +275,12 @@ nfsd_cache_lookup(struct svc_rqst *rqstp) 
	if (!list_empty(&lru_head)) {

		rp = list_first_entry(&lru_head, struct svc_cacherep, c_lru);

		if (nfsd_cache_entry_expired(rp) ||

		    num_drc_entries >= max_drc_entries)

		    num_drc_entries >= max_drc_entries) {

			lru_put_end(rp);

			prune_cache_entries();

			goto setup_entry;

		}

	}



	spin_unlock(&cache_lock);

	rp = nfsd_reply_cache_alloc();