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

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On 13/12/2022 02:02, Jeff Layton wrote:
On Mon, 2022-12-12 at 18:56 +0100, Ilya Dryomov wrote:
On Fri, Nov 18, 2022 at 3:07 AM <xiubli@xxxxxxxxxx> wrote:
From: Xiubo Li <xiubli@xxxxxxxxxx>

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@xxxxxxxxxxxxxxx
Cc: Jeff Layton <jlayton@xxxxxxxxxx>
URL: https://tracker.ceph.com/issues/57986
Signed-off-by: Xiubo Li <xiubli@xxxxxxxxxx>
---
  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;
Hi Xiubo and Jeff,

Xiubo, instead of defining struct ceph_lock_info and including
a CephFS-specific header file in linux/fs.h, I think we should repeat
what was done for AFS -- particularly given that ceph_lock_info ends up
being a dummy type that isn't mentioned anywhere else.

Jeff, could you please ack this with your file locking hat on?

ACK. I think that would be cleaner.

Sure, will fix this.

Thanks,

- Xiubo


Thanks




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