Re: NFS woes again Was: [linux-usb-devel] USB-related oops insysfs with linux v2.6.23-rc3-50-g28e8351

[Trond Myklebust]

On Thu, 2007-08-23 at 12:36 -0500, Florin Iucha wrote:
> On Thu, Aug 23, 2007 at 10:14:38AM -0700, Bret Towe wrote:
> > this sounds alot like the post i did yesterday titled 'nfs4 hang regression'
> > i tracked it down to commit 3d39c691ff486142dd9aaeac12f553f4476b7a6
> 
> Yes, it certainly does -- all the symptoms match!
> 
> I'm not [alone in] seeing dead keyboards!
> 
> Now, if only somebody could clarify to me the connection between
> the bad NFS4 shooting the keyboard but not the mouse, that would
> be wonderful.
> 
> florin

Could you and Bret please check if the attached patch fixes the hang?

Cheers
  Trond


> --- Begin Message ---
> We need to ensure that nobody adds anything to nfs_automount_list while we
> are killing off the work queue entry, or else nfs_expire_automounts will
> simply rearm it, and we hang.
>
> Signed-off-by: Trond Myklebust <Trond.Myklebust@xxxxxxxxxx>
> ---
>
>  fs/nfs/namespace.c |   14 +++++++++++++-
>  1 files changed, 13 insertions(+), 1 deletions(-)
>
> diff --git a/fs/nfs/namespace.c b/fs/nfs/namespace.c
> index aea76d0..bcd0777 100644
> --- a/fs/nfs/namespace.c
> +++ b/fs/nfs/namespace.c
> @@ -22,6 +22,11 @@ static void nfs_expire_automounts(struct work_struct *work);
>  
>  LIST_HEAD(nfs_automount_list);
>  static DECLARE_DELAYED_WORK(nfs_automount_task, nfs_expire_automounts);
> +/*
> + * The following mutex prevents nfs_follow_mountpoint from adding new
> + * entries to nfs_automount_list
> + */
> +static DEFINE_MUTEX(nfs_automount_mutex);
>  int nfs_mountpoint_expiry_timeout = 500 * HZ;
>  
>  static struct vfsmount *nfs_do_submount(const struct vfsmount *mnt_parent,
> @@ -128,18 +133,21 @@ static void * nfs_follow_mountpoint(struct dentry *dentry, struct nameidata *nd)
>  		goto out_err;
>  
>  	mntget(mnt);
> +	mutex_lock(&nfs_automount_mutex);
>  	err = do_add_mount(mnt, nd, nd->mnt->mnt_flags|MNT_SHRINKABLE, &nfs_automount_list);
>  	if (err < 0) {
> +		mutex_unlock(&nfs_automount_mutex);
>  		mntput(mnt);
>  		if (err == -EBUSY)
>  			goto out_follow;
>  		goto out_err;
>  	}
> +	schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
> +	mutex_unlock(&nfs_automount_mutex);
>  	mntput(nd->mnt);
>  	dput(nd->dentry);
>  	nd->mnt = mnt;
>  	nd->dentry = dget(mnt->mnt_root);
> -	schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
>  out:
>  	dprintk("%s: done, returned %d\n", __FUNCTION__, err);
>  
> @@ -175,8 +183,12 @@ static void nfs_expire_automounts(struct work_struct *work)
>  
>  void nfs_release_automount_timer(void)
>  {
> +	if (!list_empty(&nfs_automount_list))
> +		return;
> +	mutex_lock(&nfs_automount_mutex);
>  	if (list_empty(&nfs_automount_list))
>  		cancel_delayed_work_sync(&nfs_automount_task);
> +	mutex_unlock(&nfs_automount_mutex);
>  }
>  
>  /*
>
> --- End Message ---