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

[Ilya Dryomov]

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?

Thanks,

                Ilya