From: Trond Myklebust <trond.myklebust@hammerspace.com>
Date: Tue, 11 May 2021 23:41:10 -0400
Subject: [PATCH] NFS: nfs_find_open_context() may only select open files
Git-commit: e97bc66377bca097e1f3349ca18ca17f202ff659
Patch-mainline: v5.14
References: git-fixes

If a file has already been closed, then it should not be selected to
support further I/O.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
[trond: Fix an invalid pointer deref reported by Colin Ian King]
Acked-by: NeilBrown <neilb@suse.com>

---
 fs/nfs/inode.c         |    4 ++++
 include/linux/nfs_fs.h |    1 +
 2 files changed, 5 insertions(+)

--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -940,6 +940,7 @@ EXPORT_SYMBOL_GPL(nfs_inode_attach_open_
 void nfs_file_set_open_context(struct file *filp, struct nfs_open_context *ctx)
 {
 	filp->private_data = get_nfs_open_context(ctx);
+	set_bit(NFS_CONTEXT_FILE_OPEN, &ctx->flags);
 	if (list_empty(&ctx->list))
 		nfs_inode_attach_open_context(ctx);
 }
@@ -959,6 +960,8 @@ struct nfs_open_context *nfs_find_open_c
 			continue;
 		if ((pos->mode & (FMODE_READ|FMODE_WRITE)) != mode)
 			continue;
+		if (!test_bit(NFS_CONTEXT_FILE_OPEN, &pos->flags))
+			continue;
 		ctx = get_nfs_open_context(pos);
 		break;
 	}
@@ -973,6 +976,7 @@ void nfs_file_clear_open_context(struct
 	if (ctx) {
 		struct inode *inode = d_inode(ctx->dentry);
 
+		clear_bit(NFS_CONTEXT_FILE_OPEN, &ctx->flags);
 		/*
 		 * We fatal error on write before. Try to writeback
 		 * every page again.
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -77,6 +77,7 @@ struct nfs_open_context {
 #define NFS_CONTEXT_RESEND_WRITES	(1)
 #define NFS_CONTEXT_BAD			(2)
 #define NFS_CONTEXT_UNLOCK	(3)
+#define NFS_CONTEXT_FILE_OPEN		(4)
 	int error;
 
 	struct list_head list;