NFSv4.2: Always flush out writes in nfs42_proc_fallocate()

stable inclusion
from stable-5.10.38
commit cbc868ea28a8db2daab63cfb4d8c08ccafda5c10
bugzilla: 51875
CVE: NA

--------------------------------

[ Upstream commit 99f23783 ]

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

Fixes: 1e564d3d ("NFSv4.2: Fix a race in nfs42_proc_deallocate()")
Signed-off-by: NTrond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Acked-by: NWeilong Chen <chenweilong@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

fs/nfs/nfs42proc.c

@@ -90,7 +90,8 @@ static int _nfs42_proc_fallocate(struct rpc_message *msg, struct file *filep,
 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;
@@ -99,9 +100,13 @@ static int nfs42_proc_fallocate(struct rpc_message *msg, struct file *filep,
 	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) {
@@ -110,7 +115,7 @@ static int nfs42_proc_fallocate(struct rpc_message *msg, struct file *filep,
 		}
 		err = nfs4_handle_exception(server, err, &exception);
 	} while (exception.retry);
-
+out:
 	nfs_put_lock_context(lock);
 	return err;
 }
@@ -148,16 +153,13 @@ int nfs42_proc_deallocate(struct file *filep, loff_t offset, loff_t len)
 		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;
 }