NFS: Fix deadlocks in nfs_scan_commit_list()

Partially revert commit 2ce209c42c01 ("NFS: Wait for requests that are
locked on the commit list"), since it can lead to deadlocks between
commit requests and nfs_join_page_group().
For now we should assume that any locked requests on the commit list are
either about to be removed and committed by another task, or the writes
they describe are about to be retransmitted. In either case, we should
not need to worry.

Fixes: 2ce209c42c01 ("NFS: Wait for requests that are locked on the commit list")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index b89d5ef3af0e485d61f2887c4d7ee1dc0dae4fa2..38f181e1343a48f1e94b0f5baf4024de52f0cd43 100644 (file)
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -1039,25 +1039,11 @@ nfs_scan_commit_list(struct list_head *src, struct list_head *dst,
        struct nfs_page *req, *tmp;
        int ret = 0;
 
-restart:
        list_for_each_entry_safe(req, tmp, src, wb_list) {
                kref_get(&req->wb_kref);
                if (!nfs_lock_request(req)) {
-                       int status;
-
-                       /* Prevent deadlock with nfs_lock_and_join_requests */
-                       if (!list_empty(dst)) {
-                               nfs_release_request(req);
-                               continue;
-                       }
-                       /* Ensure we make progress to prevent livelock */
-                       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;
-                       goto restart;
+                       continue;
                }
                nfs_request_remove_commit_list(req, cinfo);
                clear_bit(PG_COMMIT_TO_DS, &req->wb_flags);
@@ -1952,6 +1938,7 @@ static int __nfs_commit_inode(struct inode *inode, int how,
        int may_wait = how & FLUSH_SYNC;
        int ret, nscan;
 
+       how &= ~FLUSH_SYNC;
        nfs_init_cinfo_from_inode(&cinfo, inode);
        nfs_commit_begin(cinfo.mds);
        for (;;) {