SUNRPC: Fix up backchannel slot table accounting

Add a per-transport maximum limit in the socket case, and add
helpers to allow the NFSv4 code to discover that limit.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 52de7245a2ee..39896afc6edf 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -8380,6 +8380,7 @@ static void nfs4_init_channel_attrs(struct nfs41_create_session_args *args,
 {
         unsigned int max_rqst_sz, max_resp_sz;
         unsigned int max_bc_payload = rpc_max_bc_payload(clnt);
+        unsigned int max_bc_slots = rpc_num_bc_slots(clnt);
 
         max_rqst_sz = NFS_MAX_FILE_IO_SIZE + nfs41_maxwrite_overhead;
         max_resp_sz = NFS_MAX_FILE_IO_SIZE + nfs41_maxread_overhead;
@@ -8402,6 +8403,8 @@ static void nfs4_init_channel_attrs(struct nfs41_create_session_args *args,
         args->bc_attrs.max_resp_sz_cached = 0;
         args->bc_attrs.max_ops = NFS4_MAX_BACK_CHANNEL_OPS;
         args->bc_attrs.max_reqs = max_t(unsigned short, max_session_cb_slots, 1);
+        if (args->bc_attrs.max_reqs > max_bc_slots)
+                args->bc_attrs.max_reqs = max_bc_slots;
 
         dprintk("%s: Back Channel : max_rqst_sz=%u max_resp_sz=%u "
                 "max_resp_sz_cached=%u max_ops=%u max_reqs=%u\n",