Re: [PATCH] xfs/log: protect xc_cil in xlog_cil_push()

[Brian Foster <bfoster@redhat.com>]

On Wed, Oct 30, 2019 at 02:29:40PM +0800, Pingfan Liu wrote:
> xlog_cil_push() is the reader and writer of xc_cil, and should be protected
> against xlog_cil_insert_items().
> 
> Signed-off-by: Pingfan Liu <kernelfans@gmail.com>
> Cc: "Darrick J. Wong" <darrick.wong@oracle.com>
> To: linux-xfs@vger.kernel.org
> Cc: linux-fsdevel@vger.kernel.org
> ---
>  fs/xfs/xfs_log_cil.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/fs/xfs/xfs_log_cil.c b/fs/xfs/xfs_log_cil.c
> index ef652abd..004af09 100644
> --- a/fs/xfs/xfs_log_cil.c
> +++ b/fs/xfs/xfs_log_cil.c
> @@ -723,6 +723,7 @@ xlog_cil_push(
>  	 */
>  	lv = NULL;
>  	num_iovecs = 0;
> +	spin_lock(&cil->xc_cil_lock);
>  	while (!list_empty(&cil->xc_cil)) {
>  		struct xfs_log_item	*item;
>  
> @@ -737,6 +738,7 @@ xlog_cil_push(
>  		item->li_lv = NULL;
>  		num_iovecs += lv->lv_niovecs;
>  	}
> +	spin_unlock(&cil->xc_cil_lock);

The majority of this function executes under exclusive ->xc_ctx_lock.
xlog_cil_insert_items() runs with the ->xc_ctx_lock taken in read mode.
The ->xc_cil_lock spinlock is used in the latter case to protect the
list under concurrent transaction commits.

Brian

>  
>  	/*
>  	 * initialise the new context and attach it to the CIL. Then attach
> -- 
> 2.7.5
>