From: Trond Myklebust <trond.myklebust@hammerspace.com>
Date: Sun, 28 Mar 2021 18:17:14 -0400
Subject: [PATCH] NFSv4.2: Always flush out writes in nfs42_proc_fallocate()
Git-commit: 99f23783224355e7022ceea9b8d9f62c0fd01bd8
Patch-mainline: v5.13
References: git-fixes

Whether we're allocating or delallocating space, we should flush out the
pending writes in order to avoid races with attribute updates.

Fixes: 1e564d3dbd68 ("NFSv4.2: Fix a race in nfs42_proc_deallocate()")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Acked-by: NeilBrown <neilb@suse.com>

---
 fs/nfs/nfs42proc.c |   16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

--- a/fs/nfs/nfs42proc.c
+++ b/fs/nfs/nfs42proc.c
@@ -57,7 +57,8 @@ static int _nfs42_proc_fallocate(struct
 static int nfs42_proc_fallocate(struct rpc_message *msg, struct file *filep,
 				loff_t offset, loff_t len)
 {
-	struct nfs_server *server = NFS_SERVER(file_inode(filep));
+	struct inode *inode = file_inode(filep);
+	struct nfs_server *server = NFS_SERVER(inode);
 	struct nfs4_exception exception = { };
 	struct nfs_lock_context *lock;
 	int err;
@@ -66,9 +67,13 @@ static int nfs42_proc_fallocate(struct r
 	if (IS_ERR(lock))
 		return PTR_ERR(lock);
 
-	exception.inode = file_inode(filep);
+	exception.inode = inode;
 	exception.state = lock->open_context->state;
 
+	err = nfs_sync_inode(inode);
+	if (err)
+		goto out;
+
 	do {
 		err = _nfs42_proc_fallocate(msg, filep, lock, offset, len);
 		if (err == -ENOTSUPP) {
@@ -77,7 +82,7 @@ static int nfs42_proc_fallocate(struct r
 		}
 		err = nfs4_handle_exception(server, err, &exception);
 	} while (exception.retry);
-
+out:
 	nfs_put_lock_context(lock);
 	return err;
 }
@@ -115,16 +120,13 @@ int nfs42_proc_deallocate(struct file *f
 		return -EOPNOTSUPP;
 
 	inode_lock(inode);
-	err = nfs_sync_inode(inode);
-	if (err)
-		goto out_unlock;
 
 	err = nfs42_proc_fallocate(&msg, filep, offset, len);
 	if (err == 0)
 		truncate_pagecache_range(inode, offset, (offset + len) -1);
 	if (err == -EOPNOTSUPP)
 		NFS_SERVER(inode)->caps &= ~NFS_CAP_DEALLOCATE;
-out_unlock:
+
 	inode_unlock(inode);
 	return err;
 }