From: Scott Mayhew <smayhew@redhat.com>
Date: Sat, 1 Aug 2020 07:10:38 -0400
Subject: [PATCH] nfs: ensure correct writeback errors are returned on close()
Git-commit: 67dd23f9e6fbaf163431912ef5599c5e0693476c
Patch-mainline: v5.9-rc1
References: git-fixes

nfs_wb_all() calls filemap_write_and_wait(), which uses
filemap_check_errors() to determine the error to return.
filemap_check_errors() only looks at the mapping->flags and will
therefore only return either -ENOSPC or -EIO.  To ensure that the
correct error is returned on close(), nfs{,4}_file_flush() should call
filemap_check_wb_err() which looks at the errseq value in
mapping->wb_err without consuming it.

Fixes: 6fbda89b257f ("NFS: Replace custom error reporting mechanism with
generic one")

Signed-off-by: Scott Mayhew <smayhew@redhat.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Acked-by: NeilBrown <neilb@suse.com>

---
 fs/nfs/file.c     |    5 ++++-
 fs/nfs/nfs4file.c |    5 ++++-
 2 files changed, 8 insertions(+), 2 deletions(-)

--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -152,6 +152,7 @@ static int
 nfs_file_flush(struct file *file, fl_owner_t id)
 {
 	struct inode	*inode = file_inode(file);
+	errseq_t since;
 
 	dprintk("NFS: flush(%pD2)\n", file);
 
@@ -160,7 +161,9 @@ nfs_file_flush(struct file *file, fl_own
 		return 0;
 
 	/* Flush writes to the server and return any errors */
-	return nfs_wb_all(inode);
+	since = filemap_sample_wb_err(file->f_mapping);
+	nfs_wb_all(inode);
+	return filemap_check_wb_err(file->f_mapping, since);
 }
 
 ssize_t
--- a/fs/nfs/nfs4file.c
+++ b/fs/nfs/nfs4file.c
@@ -110,6 +110,7 @@ static int
 nfs4_file_flush(struct file *file, fl_owner_t id)
 {
 	struct inode	*inode = file_inode(file);
+	errseq_t since;
 
 	dprintk("NFS: flush(%pD2)\n", file);
 
@@ -125,7 +126,9 @@ nfs4_file_flush(struct file *file, fl_ow
 		return filemap_fdatawrite(file->f_mapping);
 
 	/* Flush writes to the server and return any errors */
-	return nfs_wb_all(inode);
+	since = filemap_sample_wb_err(file->f_mapping);
+	nfs_wb_all(inode);
+	return filemap_check_wb_err(file->f_mapping, since);
 }
 
 #ifdef CONFIG_NFS_V4_2