linux-kernel - Re: [PATCH] ocfs2: fix unbalanced locking

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Date:   Mon, 27 Jul 2020 15:15:04 +0800
From:   Joseph Qi <joseph.qi@...ux.alibaba.com>
To:     Pavel Machek <pavel@....cz>, trivial@...nel.org, mark@...heh.com,
        jlbec@...lplan.org, ocfs2-devel@....oracle.com,
        linux-kernel@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Junxiao Bi <junxiao.bi@...cle.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] ocfs2: fix unbalanced locking



On 2020/7/24 20:44, Pavel Machek wrote:
> 
> Based on what fails, function can return with nfs_sync_rwlock either
> locked or unlocked. That can not be right.
> 
> Always return with lock unlocked on error.
> 
> Signed-off-by: Pavel Machek (CIP) <pavel@...x.de>

Looks good.

Fixes: 4cd9973f9ff6 ("ocfs2: avoid inode removal while nfsd is accessing it")
Reviewed-by: Joseph Qi <joseph.qi@...ux.alibaba.com>

> 
> diff --git a/fs/ocfs2/dlmglue.c b/fs/ocfs2/dlmglue.c
> index 751bc4dc7466..8e3a369086db 100644
> --- a/fs/ocfs2/dlmglue.c
> +++ b/fs/ocfs2/dlmglue.c
> @@ -2871,9 +2871,15 @@ int ocfs2_nfs_sync_lock(struct ocfs2_super *osb, int ex)
>  
>  	status = ocfs2_cluster_lock(osb, lockres, ex ? LKM_EXMODE : LKM_PRMODE,
>  				    0, 0);
> -	if (status < 0)
> +	if (status < 0) {
>  		mlog(ML_ERROR, "lock on nfs sync lock failed %d\n", status);
>  
> +		if (ex)
> +			up_write(&osb->nfs_sync_rwlock);
> +		else
> +			up_read(&osb->nfs_sync_rwlock);
> +	}
> +
>  	return status;
>  }
>  
>