linux-kernel - Re: [PATCH v4 2/2] ceph: add ceph specific member support for file

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Date:   Tue, 13 Dec 2022 19:05:47 +0100
From:   Ilya Dryomov <idryomov@...il.com>
To:     xiubli@...hat.com
Cc:     jlayton@...nel.org, ceph-devel@...r.kernel.org,
        mchangir@...hat.com, lhenriques@...e.de, viro@...iv.linux.org.uk,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH v4 2/2] ceph: add ceph specific member support for file_lock

On Tue, Dec 13, 2022 at 1:11 PM <xiubli@...hat.com> wrote:
>
> From: Xiubo Li <xiubli@...hat.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@...r.kernel.org
> Cc: Jeff Layton <jlayton@...nel.org>
> URL: https://tracker.ceph.com/issues/57986
> Signed-off-by: Xiubo Li <xiubli@...hat.com>
> ---
>  fs/ceph/locks.c    | 20 ++++++++++++++++++--
>  include/linux/fs.h |  3 +++
>  2 files changed, 21 insertions(+), 2 deletions(-)
>
> diff --git a/fs/ceph/locks.c b/fs/ceph/locks.c
> index b191426bf880..cf78608a3f9a 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_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_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_inode = NULL;
> +       iput(inode);
>  }
>
>  static const struct file_lock_operations ceph_fl_lock_ops = {
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 7b52fdfb6da0..6106374f5257 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1119,6 +1119,9 @@ struct file_lock {
>                         int state;              /* state of grant or error if -ve */
>                         unsigned int    debug_id;
>                 } afs;
> +               struct {
> +                       struct inode *fl_inode;

Hi Xiubo,

Nit: I think it could be just "inode", without the prefix which is
already present in the union field name.

Thanks,

                Ilya