From: Trond Myklebust <trond.myklebust@hammerspace.com>
Date: Mon, 4 Oct 2021 15:37:42 -0400
Subject: [PATCH] NFS: Fix up commit deadlocks
Git-commit: 133a48abf6ecc535d7eddc6da1c3e4c972445882
Patch-mainline: v5.16-rc1
References: git-fixes

If O_DIRECT bumps the commit_info rpcs_out field, then that could lead
to fsync() hangs. The fix is to ensure that O_DIRECT calls
nfs_commit_end().

Fixes: 723c921e7dfc ("sched/wait, fs/nfs: Convert wait_on_atomic_t() usage to the new wait_var_event() API")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Acked-by: NeilBrown <neilb@suse.com>

---
 fs/nfs/direct.c        |    2 +-
 fs/nfs/write.c         |    7 +++++--
 include/linux/nfs_fs.h |    1 +
 3 files changed, 7 insertions(+), 3 deletions(-)

--- a/fs/nfs/direct.c
+++ b/fs/nfs/direct.c
@@ -739,7 +739,7 @@ static void nfs_direct_commit_complete(s
 		nfs_unlock_and_release_request(req);
 	}
 
-	if (atomic_dec_and_test(&cinfo.mds->rpcs_out))
+	if (nfs_commit_end(cinfo.mds))
 		nfs_direct_write_complete(dreq);
 }
 
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -1666,10 +1666,13 @@ static void nfs_commit_begin(struct nfs_
 	atomic_inc(&cinfo->rpcs_out);
 }
 
-static void nfs_commit_end(struct nfs_mds_commit_info *cinfo)
+bool nfs_commit_end(struct nfs_mds_commit_info *cinfo)
 {
-	if (atomic_dec_and_test(&cinfo->rpcs_out))
+	if (atomic_dec_and_test(&cinfo->rpcs_out)) {
 		wake_up_var(&cinfo->rpcs_out);
+		return true;
+	}
+	return false;
 }
 
 void nfs_commitdata_release(struct nfs_commit_data *data)
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -545,6 +545,7 @@ extern int nfs_wb_page_cancel(struct ino
 extern int  nfs_commit_inode(struct inode *, int);
 extern struct nfs_commit_data *nfs_commitdata_alloc(bool never_fail);
 extern void nfs_commit_free(struct nfs_commit_data *data);
+bool nfs_commit_end(struct nfs_mds_commit_info *cinfo);
 
 static inline int
 nfs_have_writebacks(struct inode *inode)