Commit a9507f6a authored by Chuck Lever's avatar Chuck Lever
Browse files

NFSD: Replace nfsd_prune_bucket() 



Enable nfsd_prune_bucket() to drop the bucket lock while calling
kfree(). Use the same pattern that Jeff recently introduced in the
NFSD filecache.

A few percpu operations are moved outside the lock since they
temporarily disable local IRQs which is expensive and does not
need to be done while the lock is held.

Reviewed-by: default avatarJeff Layton <jlayton@kernel.org>
Signed-off-by: default avatarChuck Lever <chuck.lever@oracle.com>
parent ff0d1693

fs/nfsd/nfscache.c

+63 −15
Original line number Diff line number Diff line
@@ -117,6 +117,21 @@ static void nfsd_cacherep_free(struct svc_cacherep *rp) 
	kmem_cache_free(drc_slab, rp);

}



static unsigned long

nfsd_cacherep_dispose(struct list_head *dispose)

{

	struct svc_cacherep *rp;

	unsigned long freed = 0;



	while (!list_empty(dispose)) {

		rp = list_first_entry(dispose, struct svc_cacherep, c_lru);

		list_del(&rp->c_lru);

		nfsd_cacherep_free(rp);

		freed++;

	}

	return freed;

}



static void

nfsd_cacherep_unlink_locked(struct nfsd_net *nn, struct nfsd_drc_bucket *b,

			    struct svc_cacherep *rp)
@@ -260,6 +275,41 @@ nfsd_cache_bucket_find(__be32 xid, struct nfsd_net *nn) 
	return &nn->drc_hashtbl[hash];

}



/*

 * Remove and return no more than @max expired entries in bucket @b.

 * If @max is zero, do not limit the number of removed entries.

 */

static void

nfsd_prune_bucket_locked(struct nfsd_net *nn, struct nfsd_drc_bucket *b,

			 unsigned int max, struct list_head *dispose)

{

	unsigned long expiry = jiffies - RC_EXPIRE;

	struct svc_cacherep *rp, *tmp;

	unsigned int freed = 0;



	lockdep_assert_held(&b->cache_lock);



	/* The bucket LRU is ordered oldest-first. */

	list_for_each_entry_safe(rp, tmp, &b->lru_head, c_lru) {

		/*

		 * Don't free entries attached to calls that are still

		 * in-progress, but do keep scanning the list.

		 */

		if (rp->c_state == RC_INPROG)

			continue;



		if (atomic_read(&nn->num_drc_entries) <= nn->max_drc_entries &&

		    time_before(expiry, rp->c_timestamp))

			break;



		nfsd_cacherep_unlink_locked(nn, b, rp);

		list_add(&rp->c_lru, dispose);



		if (max && ++freed > max)

			break;

	}

}



static long prune_bucket(struct nfsd_drc_bucket *b, struct nfsd_net *nn,

			 unsigned int max)

{
@@ -283,11 +333,6 @@ static long prune_bucket(struct nfsd_drc_bucket *b, struct nfsd_net *nn, 
	return freed;

}



static long nfsd_prune_bucket(struct nfsd_drc_bucket *b, struct nfsd_net *nn)

{

	return prune_bucket(b, nn, 3);

}



/*

 * 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.
@@ -443,6 +488,8 @@ int nfsd_cache_lookup(struct svc_rqst *rqstp) 
	__wsum			csum;

	struct nfsd_drc_bucket	*b;

	int type = rqstp->rq_cachetype;

	unsigned long freed;

	LIST_HEAD(dispose);

	int rtn = RC_DOIT;



	rqstp->rq_cacherep = NULL;
@@ -467,20 +514,18 @@ int nfsd_cache_lookup(struct svc_rqst *rqstp) 
	found = nfsd_cache_insert(b, rp, nn);

	if (found != rp)

		goto found_entry;



	nfsd_stats_rc_misses_inc();

	rqstp->rq_cacherep = rp;

	rp->c_state = RC_INPROG;

	nfsd_prune_bucket_locked(nn, b, 3, &dispose);

	spin_unlock(&b->cache_lock);



	freed = nfsd_cacherep_dispose(&dispose);

	trace_nfsd_drc_gc(nn, freed);



	nfsd_stats_rc_misses_inc();

	atomic_inc(&nn->num_drc_entries);

	nfsd_stats_drc_mem_usage_add(nn, sizeof(*rp));



	nfsd_prune_bucket(b, nn);



out_unlock:

	spin_unlock(&b->cache_lock);

out:

	return rtn;

	goto out;



found_entry:

	/* We found a matching entry which is either in progress or done. */
@@ -518,7 +563,10 @@ int nfsd_cache_lookup(struct svc_rqst *rqstp) 


out_trace:

	trace_nfsd_drc_found(nn, rqstp, rtn);

	goto out_unlock;

out_unlock:

	spin_unlock(&b->cache_lock);

out:

	return rtn;

}



/**

fs/nfsd/trace.h

+22 −0
Original line number Diff line number Diff line
@@ -1262,6 +1262,28 @@ TRACE_EVENT(nfsd_drc_mismatch, 
		__entry->ingress)

);



TRACE_EVENT_CONDITION(nfsd_drc_gc,

	TP_PROTO(

		const struct nfsd_net *nn,

		unsigned long freed

	),

	TP_ARGS(nn, freed),

	TP_CONDITION(freed > 0),

	TP_STRUCT__entry(

		__field(unsigned long long, boot_time)

		__field(unsigned long, freed)

		__field(int, total)

	),

	TP_fast_assign(

		__entry->boot_time = nn->boot_time;

		__entry->freed = freed;

		__entry->total = atomic_read(&nn->num_drc_entries);

	),

	TP_printk("boot_time=%16llx total=%d freed=%lu",

		__entry->boot_time, __entry->total, __entry->freed

	)

);



TRACE_EVENT(nfsd_cb_args,

	TP_PROTO(

		const struct nfs4_client *clp,