NFSv4.1: Remove a bogus BUG_ON() in nfs4_layoutreturn_done

Ever since commit 0a57cdac3f (NFSv4.1 send layoutreturn to fence
disconnected data server) we've been sending layoutreturn calls
while there is potentially still outstanding I/O to the data
servers. The reason we do this is to avoid races between replayed
writes to the MDS and the original writes to the DS.

When this happens, the BUG_ON() in nfs4_layoutreturn_done can
be triggered because it assumes that we would never call
layoutreturn without knowing that all I/O to the DS is
finished. The fix is to remove the BUG_ON() now that the
assumptions behind the test are obsolete.

Reported-by: Boaz Harrosh <bharrosh@panasas.com>
Reported-by: Tigran Mkrtchyan <tigran.mkrtchyan@desy.de>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: stable@vger.kernel.org [>=3.5]

1 files changed, 2 insertions, 6 deletions

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index f94f6b3928fc..c77d296bdaa6 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -6359,12 +6359,8 @@ static void nfs4_layoutreturn_done(struct rpc_task *task, void *calldata)
                 return;
         }
         spin_lock(&lo->plh_inode->i_lock);
-        if (task->tk_status == 0) {
-                if (lrp->res.lrs_present) {
-                        pnfs_set_layout_stateid(lo, &lrp->res.stateid, true);
-                } else
-                        BUG_ON(!list_empty(&lo->plh_segs));
-        }
+        if (task->tk_status == 0 && lrp->res.lrs_present)
+                pnfs_set_layout_stateid(lo, &lrp->res.stateid, true);
         lo->plh_block_lgets--;
         spin_unlock(&lo->plh_inode->i_lock);
         dprintk("<-- %s\n", __func__);