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

[Jeff Layton]

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.

Thanks
-- 
Jeff Layton <jlayton@xxxxxxxxxx>