[PATCH 2/2 v3] ceph: add ceph_lock_info support for file_lock

[xiubli@redhat.com]

From: Xiubo Li <xiubli@redhat.com>

When ceph releasing the file_lock it will try to get the inode pointer
from the fl->fl_file, which the memory could already be released by
another thread in filp_close(). Because in VFS layer the fl->fl_file
doesn't increase the file's reference counter.

Will switch to use ceph dedicate lock info to track the inode.

And in ceph_fl_release_lock() we should skip all the operations if
the fl->fl_u.ceph_fl.fl_inode is not set, which should come from
the request file_lock. And we will set fl->fl_u.ceph_fl.fl_inode when
inserting it to the inode lock list, which is when copying the lock.

Cc: stable@vger.kernel.org
Cc: Jeff Layton <jlayton@kernel.org>
URL: https://tracker.ceph.com/issues/57986
Signed-off-by: Xiubo Li <xiubli@redhat.com>
---
 fs/ceph/locks.c                 | 20 ++++++++++++++++++--
 include/linux/ceph/ceph_fs_fl.h | 17 +++++++++++++++++
 include/linux/fs.h              |  2 ++
 3 files changed, 37 insertions(+), 2 deletions(-)
 create mode 100644 include/linux/ceph/ceph_fs_fl.h

diff --git a/fs/ceph/locks.c b/fs/ceph/locks.c
index b191426bf880..621f38f10a88 100644
--- a/fs/ceph/locks.c
+++ b/fs/ceph/locks.c
@@ -34,18 +34,34 @@ static void ceph_fl_copy_lock(struct file_lock *dst, struct file_lock *src)
 {
 	struct inode *inode = file_inode(dst->fl_file);
 	atomic_inc(&ceph_inode(inode)->i_filelock_ref);
+	dst->fl_u.ceph_fl.fl_inode = igrab(inode);
 }
 
+/*
+ * Do not use the 'fl->fl_file' in release function, which
+ * is possibly already released by another thread.
+ */
 static void ceph_fl_release_lock(struct file_lock *fl)
 {
-	struct inode *inode = file_inode(fl->fl_file);
-	struct ceph_inode_info *ci = ceph_inode(inode);
+	struct inode *inode = fl->fl_u.ceph_fl.fl_inode;
+	struct ceph_inode_info *ci;
+
+	/*
+	 * If inode is NULL it should be a request file_lock,
+	 * nothing we can do.
+	 */
+	if (!inode)
+		return;
+
+	ci = ceph_inode(inode);
 	if (atomic_dec_and_test(&ci->i_filelock_ref)) {
 		/* clear error when all locks are released */
 		spin_lock(&ci->i_ceph_lock);
 		ci->i_ceph_flags &= ~CEPH_I_ERROR_FILELOCK;
 		spin_unlock(&ci->i_ceph_lock);
 	}
+	fl->fl_u.ceph_fl.fl_inode = NULL;
+	iput(inode);
 }
 
 static const struct file_lock_operations ceph_fl_lock_ops = {
diff --git a/include/linux/ceph/ceph_fs_fl.h b/include/linux/ceph/ceph_fs_fl.h
new file mode 100644
index 000000000000..ad1cf96329f9
--- /dev/null
+++ b/include/linux/ceph/ceph_fs_fl.h
@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * ceph_fs_fl.h - Ceph lock info
+ *
+ * LGPL2
+ */
+
+#ifndef CEPH_FS_FL_H
+#define CEPH_FS_FL_H
+
+#include <linux/fs.h>
+
+struct ceph_lock_info {
+	struct inode *fl_inode;
+};
+
+#endif
diff --git a/include/linux/fs.h b/include/linux/fs.h
index d6cb42b7e91c..2b03d5e375d7 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1066,6 +1066,7 @@ bool opens_in_grace(struct net *);
 
 /* that will die - we need it for nfs_lock_info */
 #include <linux/nfs_fs_i.h>
+#include <linux/ceph/ceph_fs_fl.h>
 
 /*
  * struct file_lock represents a generic "file lock". It's used to represent
@@ -1119,6 +1120,7 @@ struct file_lock {
 			int state;		/* state of grant or error if -ve */
 			unsigned int	debug_id;
 		} afs;
+		struct ceph_lock_info	ceph_fl;
 	} fl_u;
 } __randomize_layout;
 
-- 
2.31.1