ocfs2: fix reflink preserve cleanup issue

[ Upstream commit 5138c93 ]

commit c06c303 ("ocfs2: fix xattr array entry __counted_by error")
doesn't handle all cases and the cleanup job for preserved xattr entries
still has bug:
- the 'last' pointer should be shifted by one unit after cleanup
  an array entry.
- current code logic doesn't cleanup the first entry when xh_count is 1.

Note, commit c06c303 is also a bug fix for 0fe9b66.

Link: https://lkml.kernel.org/r/20251210015725.8409-2-heming.zhao@suse.com
Fixes: 0fe9b66 ("ocfs2: Add preserve to reflink.")
Signed-off-by: Heming Zhao <heming.zhao@suse.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Joseph Qi <jiangqi903@gmail.com>
Cc: Changwei Ge <gechangwei@live.cn>
Cc: Jun Piao <piaojun@huawei.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: zhaohem

fs/ocfs2/xattr.c

@@ -6364,6 +6364,10 @@ static int ocfs2_reflink_xattr_header(handle_t *handle,
 					(void *)last - (void *)xe);
 				memset(last, 0,
 				       sizeof(struct ocfs2_xattr_entry));
+				last = &new_xh->xh_entries[le16_to_cpu(new_xh->xh_count)] - 1;
+			} else {
+				memset(xe, 0, sizeof(struct ocfs2_xattr_entry));
+				last = NULL;
 			}
 
 			/*