NFS: Wait for requests that are locked on the commit list

If a request is on the commit list, but is locked, we will currently skip
it, which can lead to livelocking when the commit count doesn't reduce
to zero.

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

1 files changed, 13 insertions, 4 deletions

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index 866702823869..5dd3b212376e 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -1030,13 +1030,22 @@ int
 nfs_scan_commit_list(struct list_head *src, struct list_head *dst,
                      struct nfs_commit_info *cinfo, int max)
 {
-        struct nfs_page *req, *tmp;
+        struct nfs_page *req;
         int ret = 0;
 
-        list_for_each_entry_safe(req, tmp, src, wb_list) {
-                if (!nfs_lock_request(req))
-                        continue;
+        while(!list_empty(src)) {
+                req = list_first_entry(src, struct nfs_page, wb_list);
                 kref_get(&req->wb_kref);
+                if (!nfs_lock_request(req)) {
+                        int status;
+                        mutex_unlock(&NFS_I(cinfo->inode)->commit_mutex);
+                        status = nfs_wait_on_request(req);
+                        nfs_release_request(req);
+                        mutex_lock(&NFS_I(cinfo->inode)->commit_mutex);
+                        if (status < 0)
+                                break;
+                        continue;
+                }
                 nfs_request_remove_commit_list(req, cinfo);
                 nfs_list_add_request(req, dst);
                 ret++;