[Cluster-devel] [DLM] keep dlm from panicing when traversing rsb list in debugfs

[Steven Whitehouse <swhiteho@redhat.com>]

Hi,

Applied to the -nmw git tree. Thanks,

Steve.

On Wed, 2007-05-16 at 15:56 -0400, Josef Bacik wrote:
> Hello,
> 
> This problem was originally reported against GFS6.1, but the same issue exists
> in upstream DLM.  This patch keeps the rsb iterator assigning under the rsbtbl
> list lock.  Each time we process an rsb we grab a reference to it to make sure
> it is not freed out from underneath us, and then put it when we get the next rsb
> in the list or move onto another list.  Thank you,
> 
> Josef
> 
> 
> Signed-off-by: Josef Bacik <jwhiter@redhat.com>
> 
> diff --git a/fs/dlm/debug_fs.c b/fs/dlm/debug_fs.c
> index 61ba670..9e27a16 100644
> --- a/fs/dlm/debug_fs.c
> +++ b/fs/dlm/debug_fs.c
> @@ -17,6 +17,7 @@
>  #include <linux/debugfs.h>
>  
>  #include "dlm_internal.h"
> +#include "lock.h"
>  
>  #define DLM_DEBUG_BUF_LEN 4096
>  static char debug_buf[DLM_DEBUG_BUF_LEN];
> @@ -166,6 +167,9 @@ static int rsb_iter_next(struct rsb_iter
>  			read_lock(&ls->ls_rsbtbl[i].lock);
>  			if (!list_empty(&ls->ls_rsbtbl[i].list)) {
>  				ri->next = ls->ls_rsbtbl[i].list.next;
> +				ri->rsb = list_entry(ri->next, struct dlm_rsb,
> +							res_hashchain);
> +				dlm_hold_rsb(ri->rsb);
>  				read_unlock(&ls->ls_rsbtbl[i].lock);
>  				break;
>  			}
> @@ -176,6 +180,7 @@ static int rsb_iter_next(struct rsb_iter
>  		if (ri->entry >= ls->ls_rsbtbl_size)
>  			return 1;
>  	} else {
> +		struct dlm_rsb *old = ri->rsb;
>  		i = ri->entry;
>  		read_lock(&ls->ls_rsbtbl[i].lock);
>  		ri->next = ri->next->next;
> @@ -184,11 +189,13 @@ static int rsb_iter_next(struct rsb_iter
>  			ri->next = NULL;
>  			ri->entry++;
>  			read_unlock(&ls->ls_rsbtbl[i].lock);
> +			dlm_put_rsb(old);
>  			goto top;
>                  }
> +		ri->rsb = list_entry(ri->next, struct dlm_rsb, res_hashchain);
>  		read_unlock(&ls->ls_rsbtbl[i].lock);
> +		dlm_put_rsb(old);
>  	}
> -	ri->rsb = list_entry(ri->next, struct dlm_rsb, res_hashchain);
>  
>  	return 0;
>  }
>