[PATCH 5/5] smb3: fix temporary data corruption in insert range

[David Howells <dhowells@xxxxxxxxxx>]

insert range doesn't discard the affected cached region
so can risk temporarily corrupting file data.

Also includes some minor cleanup (avoiding rereading
inode size repeatedly unnecessarily) to make it clearer.

Cc: stable@xxxxxxxxxxxxxxx
Fixes: 7fe6fe95b9360 ("cifs: FALLOC_FL_INSERT_RANGE support")
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>
cc: Ronnie Sahlberg <lsahlber@xxxxxxxxxx>
---

 fs/cifs/smb2ops.c |   24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index 5b5ddc1b4638..00c8d6a715c7 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -3722,35 +3722,43 @@ static long smb3_insert_range(struct file *file, struct cifs_tcon *tcon,
 	struct cifsFileInfo *cfile = file->private_data;
 	struct inode *inode = file_inode(file);
 	__le64 eof;
-	__u64  count;
+	__u64  count, old_eof;
+
+	inode_lock(inode);
 
 	xid = get_xid();
 
-	if (off >= i_size_read(inode)) {
+	old_eof = i_size_read(inode);
+	if (off >= old_eof) {
 		rc = -EINVAL;
 		goto out;
 	}
 
-	count = i_size_read(inode) - off;
-	eof = cpu_to_le64(i_size_read(inode) + len);
+	count = old_eof - off;
+	eof = cpu_to_le64(old_eof + len);
 
+	filemap_invalidate_lock(inode->i_mapping);
 	filemap_write_and_wait(inode->i_mapping);
+	truncate_pagecache_range(inode, off, old_eof);
 
 	rc = SMB2_set_eof(xid, tcon, cfile->fid.persistent_fid,
 			  cfile->fid.volatile_fid, cfile->pid, &eof);
 	if (rc < 0)
-		goto out;
+		goto out_2;
 
 	rc = smb2_copychunk_range(xid, cfile, cfile, off, count, off + len);
 	if (rc < 0)
-		goto out;
+		goto out_2;
 
-	rc = smb3_zero_range(file, tcon, off, len, 1);
+	rc = smb3_zero_data(file, tcon, off, len, xid);
 	if (rc < 0)
-		goto out;
+		goto out_2;
 
 	rc = 0;
+out_2:
+	filemap_invalidate_unlock(inode->i_mapping);
  out:
+	inode_unlock(inode);
 	free_xid(xid);
 	return rc;
 }