[PATCH v2 07/15] smb: client: drain outstanding I/O before truncating on O_TRUNC open

[Paulo Alcantara <pc@manguebit.org>]

cifs_do_truncate() flushes the pagecache with filemap_write_and_wait()
before resetting the file size to zero, but that does not wait for
direct/async I/O that was already in flight, which can complete after the
truncate and reinstate stale data past the new EOF.

Drain outstanding netfs I/O with netfs_wait_for_outstanding_io()
before resizing the file.

Reported-by: Frank Sorenson <sorenson@redhat.com>
Fixes: a8603b52b39f ("smb: client: fix data corruption with concurrent writes and O_TRUNC")
Reviewed-by: David Howells <dhowells@redhat.com>
Reviewed-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Paulo Alcantara <pc@manguebit.org>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Namjae Jeon <linkinjeon@kernel.org>
Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Cc: Shyam Prasad N <sprasad@microsoft.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Bharath SM <bharathsm@microsoft.com>
Cc: stable@vger.kernel.org
---
 fs/smb/client/file.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/smb/client/file.c b/fs/smb/client/file.c
index 4bcb87610897..11355d6bf89d 100644
--- a/fs/smb/client/file.c
+++ b/fs/smb/client/file.c
@@ -1012,6 +1012,8 @@ static int cifs_do_truncate(const unsigned int xid, struct dentry *dentry)
 	}
 	mapping_set_error(inode->i_mapping, rc);
 
+	netfs_wait_for_outstanding_io(inode);
+
 	cfile = find_writable_file(cinode, FIND_FSUID_ONLY);
 	rc = cifs_file_flush(xid, inode, cfile);
 	if (!rc) {
-- 
2.55.0