nfs: don't sleep with inode lock in lock_and_join_requests

This handles the 'nonblock=false' case in nfs_lock_and_join_requests.
If the group is already locked and blocking is allowed, drop the inode lock
and wait for the group lock to be cleared before trying it all again.
This should fix warnings found in peterz's tree (sched/wait branch), where
might_sleep() checks are added to wait.[ch].

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Weston Andros Adamson <dros@primarydata.com>
Reviewed-by: Peng Tao <tao.peng@primarydata.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

1 files changed, 11 insertions, 1 deletions

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index e056f617adf2..175d5d073ccf 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -478,13 +478,23 @@ try_again:
                 return NULL;
         }
 
-        /* lock each request in the page group */
+        /* holding inode lock, so always make a non-blocking call to try the
+         * page group lock */
         ret = nfs_page_group_lock(head, true);
         if (ret < 0) {
                 spin_unlock(&inode->i_lock);
+
+                if (!nonblock && ret == -EAGAIN) {
+                        nfs_page_group_lock_wait(head);
+                        nfs_release_request(head);
+                        goto try_again;
+                }
+
                 nfs_release_request(head);
                 return ERR_PTR(ret);
         }
+
+        /* lock each request in the page group */
         subreq = head;
         do {
                 /*