[Cluster-devel] [GFS2 Patch] GFS2: stuck in inode wait, no glocks stuck

[Steven Whitehouse]

Hi,

Now in the -nmw git tree. Thanks,

Steve.

On Tue, 2010-05-11 at 17:58 -0400, Bob Peterson wrote:
> Hi,
> 
> This patch changes the lock ordering when gfs2 reclaims
> unlinked dinodes, thereby avoiding a livelock.
> 
> Regards,
> 
> Bob Peterson
> Red Hat GFS
> 
> Signed-off-by: Bob Peterson <rpeterso at redhat.com> 
> --
> GFS2: stuck in inode wait, no glocks stuck
> 
> This patch changes the lock ordering when gfs2 reclaims
> unlinked dinodes, thereby avoiding a livelock.
> 
> rhbz#583737
> 
> diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c
> index 3739155..8bce73e 100644
> --- a/fs/gfs2/rgrp.c
> +++ b/fs/gfs2/rgrp.c
> @@ -952,16 +952,14 @@ static int try_rgrp_fit(struct gfs2_rgrpd *rgd, struct gfs2_alloc *al)
>   *          The inode, if one has been found, in inode.
>   */
>  
> -static int try_rgrp_unlink(struct gfs2_rgrpd *rgd, u64 *last_unlinked,
> -			   u64 skip, struct inode **inode)
> +static u64 try_rgrp_unlink(struct gfs2_rgrpd *rgd, u64 *last_unlinked,
> +			   u64 skip)
>  {
>  	u32 goal = 0, block;
>  	u64 no_addr;
>  	struct gfs2_sbd *sdp = rgd->rd_sbd;
>  	unsigned int n;
> -	int error = 0;
>  
> -	*inode = NULL;
>  	for(;;) {
>  		if (goal >= rgd->rd_data)
>  			break;
> @@ -981,10 +979,7 @@ static int try_rgrp_unlink(struct gfs2_rgrpd *rgd, u64 *last_unlinked,
>  		if (no_addr == skip)
>  			continue;
>  		*last_unlinked = no_addr;
> -		error = gfs2_unlinked_inode_lookup(rgd->rd_sbd->sd_vfs,
> -						   no_addr, inode);
> -		if (*inode || error)
> -			return error;
> +		return no_addr;
>  	}
>  
>  	rgd->rd_flags &= ~GFS2_RDF_CHECK;
> @@ -1069,11 +1064,12 @@ static void forward_rgrp_set(struct gfs2_sbd *sdp, struct gfs2_rgrpd *rgd)
>   * Try to acquire rgrp in way which avoids contending with others.
>   *
>   * Returns: errno
> + *          unlinked: the block address of an unlinked block to be reclaimed
>   */
>  
> -static struct inode *get_local_rgrp(struct gfs2_inode *ip, u64 *last_unlinked)
> +static int get_local_rgrp(struct gfs2_inode *ip, u64 *unlinked,
> +			  u64 *last_unlinked)
>  {
> -	struct inode *inode = NULL;
>  	struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
>  	struct gfs2_rgrpd *rgd, *begin = NULL;
>  	struct gfs2_alloc *al = ip->i_alloc;
> @@ -1082,6 +1078,7 @@ static struct inode *get_local_rgrp(struct gfs2_inode *ip, u64 *last_unlinked)
>  	int loops = 0;
>  	int error, rg_locked;
>  
> +	*unlinked = 0;
>  	rgd = gfs2_blk2rgrpd(sdp, ip->i_goal);
>  
>  	while (rgd) {
> @@ -1103,29 +1100,19 @@ static struct inode *get_local_rgrp(struct gfs2_inode *ip, u64 *last_unlinked)
>  			   because that would require an iput which can only
>  			   happen after the rgrp is unlocked. */
>  			if (!rg_locked && rgd->rd_flags & GFS2_RDF_CHECK)
> -				error = try_rgrp_unlink(rgd, last_unlinked,
> -							ip->i_no_addr, &inode);
> +				*unlinked = try_rgrp_unlink(rgd, last_unlinked,
> +							   ip->i_no_addr);
>  			if (!rg_locked)
>  				gfs2_glock_dq_uninit(&al->al_rgd_gh);
> -			if (inode) {
> -				if (error) {
> -					if (inode->i_state & I_NEW)
> -						iget_failed(inode);
> -					else
> -						iput(inode);
> -					return ERR_PTR(error);
> -				}
> -				return inode;
> -			}
> -			if (error)
> -				return ERR_PTR(error);
> +			if (*unlinked)
> +				return -EAGAIN;
>  			/* fall through */
>  		case GLR_TRYFAILED:
>  			rgd = recent_rgrp_next(rgd);
>  			break;
>  
>  		default:
> -			return ERR_PTR(error);
> +			return error;
>  		}
>  	}
>  
> @@ -1148,22 +1135,12 @@ static struct inode *get_local_rgrp(struct gfs2_inode *ip, u64 *last_unlinked)
>  			if (try_rgrp_fit(rgd, al))
>  				goto out;
>  			if (!rg_locked && rgd->rd_flags & GFS2_RDF_CHECK)
> -				error = try_rgrp_unlink(rgd, last_unlinked,
> -							ip->i_no_addr, &inode);
> +				*unlinked = try_rgrp_unlink(rgd, last_unlinked,
> +							    ip->i_no_addr);
>  			if (!rg_locked)
>  				gfs2_glock_dq_uninit(&al->al_rgd_gh);
> -			if (inode) {
> -				if (error) {
> -					if (inode->i_state & I_NEW)
> -						iget_failed(inode);
> -					else
> -						iput(inode);
> -					return ERR_PTR(error);
> -				}
> -				return inode;
> -			}
> -			if (error)
> -				return ERR_PTR(error);
> +			if (*unlinked)
> +				return -EAGAIN;
>  			break;
>  
>  		case GLR_TRYFAILED:
> @@ -1171,7 +1148,7 @@ static struct inode *get_local_rgrp(struct gfs2_inode *ip, u64 *last_unlinked)
>  			break;
>  
>  		default:
> -			return ERR_PTR(error);
> +			return error;
>  		}
>  
>  		rgd = gfs2_rgrpd_get_next(rgd);
> @@ -1180,7 +1157,7 @@ static struct inode *get_local_rgrp(struct gfs2_inode *ip, u64 *last_unlinked)
>  
>  		if (rgd == begin) {
>  			if (++loops >= 3)
> -				return ERR_PTR(-ENOSPC);
> +				return -ENOSPC;
>  			if (!skipped)
>  				loops++;
>  			flags = 0;
> @@ -1200,7 +1177,7 @@ out:
>  		forward_rgrp_set(sdp, rgd);
>  	}
>  
> -	return NULL;
> +	return 0;
>  }
>  
>  /**
> @@ -1216,7 +1193,7 @@ int gfs2_inplace_reserve_i(struct gfs2_inode *ip, char *file, unsigned int line)
>  	struct gfs2_alloc *al = ip->i_alloc;
>  	struct inode *inode;
>  	int error = 0;
> -	u64 last_unlinked = NO_BLOCK;
> +	u64 last_unlinked = NO_BLOCK, unlinked;
>  
>  	if (gfs2_assert_warn(sdp, al->al_requested))
>  		return -EINVAL;
> @@ -1232,14 +1209,19 @@ try_again:
>  	if (error)
>  		return error;
>  
> -	inode = get_local_rgrp(ip, &last_unlinked);
> -	if (inode) {
> +	error = get_local_rgrp(ip, &unlinked, &last_unlinked);
> +	if (error) {
>  		if (ip != GFS2_I(sdp->sd_rindex))
>  			gfs2_glock_dq_uninit(&al->al_ri_gh);
> -		if (IS_ERR(inode))
> -			return PTR_ERR(inode);
> -		iput(inode);
> +		if (error != -EAGAIN)
> +			return error;
> +		error = gfs2_unlinked_inode_lookup(ip->i_inode.i_sb,
> +						   unlinked, &inode);
> +		if (inode)
> +			iput(inode);
>  		gfs2_log_flush(sdp, NULL);
> +		if (error == GLR_TRYFAILED)
> +			error = 0;
>  		goto try_again;
>  	}
>