1 files changed, 15 insertions, 4 deletions

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index da1093dd5016..8622d6dd45c0 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -1575,14 +1575,25 @@ static u32 nfsd4_get_drc_mem(struct nfsd4_channel_attrs *ca)
 	unsigned long avail, total_avail;
 
 	spin_lock(&nfsd_drc_lock);
-	total_avail = nfsd_drc_max_mem - nfsd_drc_mem_used;
+	if (nfsd_drc_max_mem > nfsd_drc_mem_used)
+		total_avail = nfsd_drc_max_mem - nfsd_drc_mem_used;
+	else
+		/* We have handed out more space than we chose in
+		 * set_max_drc() to allow.  That isn't really a
+		 * problem as long as that doesn't make us think we
+		 * have lots more due to integer overflow.
+		 */
+		total_avail = 0;
 	avail = min((unsigned long)NFSD_MAX_MEM_PER_SESSION, total_avail);
 	/*
 	 * Never use more than a third of the remaining memory,
-	 * unless it's the only way to give this client a slot:
+	 * unless it's the only way to give this client a slot.
+	 * Give the client one slot even if that would require
+	 * over-allocation--it is better than failure.
 	 */
 	avail = clamp_t(unsigned long, avail, slotsize, total_avail/3);
 	num = min_t(int, num, avail / slotsize);
+	num = max_t(int, num, 1);
 	nfsd_drc_mem_used += num * slotsize;
 	spin_unlock(&nfsd_drc_lock);
 
@@ -3174,10 +3185,10 @@ static __be32 check_forechannel_attrs(struct nfsd4_channel_attrs *ca, struct nfs
 	 * performance.  When short on memory we therefore prefer to
 	 * decrease number of slots instead of their size.  Clients that
 	 * request larger slots than they need will get poor results:
+	 * Note that we always allow at least one slot, because our
+	 * accounting is soft and provides no guarantees either way.
 	 */
 	ca->maxreqs = nfsd4_get_drc_mem(ca);
-	if (!ca->maxreqs)
-		return nfserr_jukebox;
 
 	return nfs_ok;
 }