[PATCH v2 1/4] cifs: use cifs_invalidate_cache() in cifs_do_truncate() for O_TRUNC

[Frank Sorenson <sorenson@redhat.com>]

cifs_do_truncate() is invoked from cifs_open() without i_rwsem, so it
cannot use cifs_resize_file_locked() to perform a proper fscache cookie
resize.  Instead, add cifs_invalidate_cache() after cifs_setsize().

cifs_invalidate_cache() calls fscache_invalidate(), which works without
holding i_rwsem: it unconditionally increments inval_counter and sets
FSCACHE_COOKIE_NO_DATA_TO_READ, ensuring that stale cached data is not
served once the cookie is later activated by fscache_use_cookie().
Truncation to zero leaves no valid cached data, making invalidation the
correct semantic here.

Fixes: fa724e235cfd ("cifs: add fscache_resize_cookie() to cifs_setsize()")
Cc: stable@vger.kernel.org
Cc: David Howells <dhowells@redhat.com>
Cc: Paulo Alcantara <pc@manguebit.com>
Signed-off-by: Frank Sorenson <sorenson@redhat.com>
Reviewed-by: Paulo Alcantara (Red Hat) <pc@manguebit.org>
---
 fs/smb/client/file.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/smb/client/file.c b/fs/smb/client/file.c
index ac89c1ba56b1..389083f9ce00 100644
--- a/fs/smb/client/file.c
+++ b/fs/smb/client/file.c
@@ -1016,6 +1016,7 @@ static int cifs_do_truncate(const unsigned int xid, struct dentry *dentry)
 		if (!rc) {
 			netfs_resize_file(&cinode->netfs, 0, true);
 			cifs_setsize(inode, 0);
+			cifs_invalidate_cache(inode, 0);
 		}
 	}
 	if (cfile)
-- 
2.55.0