[PATCH 1/9] xfs: avoid memory allocation under m_peraglock in growfs code

[Felix Blyakher]

On Jul 18, 2009, at 5:14 PM, Christoph Hellwig wrote:

> Allocate the memory for the larger m_perag array before taking the
> per-AG lock as the per-AG lock can be taken under the i_lock which
> can be taken from reclaim context.
>
> Reported by the new reclaim context tracing in lockdep.
>
> Signed-off-by: Christoph Hellwig <hch at lst.de>

For the whole series:

Reviewed-by: Felix Blyakher <felixb at sgi.com>

>
>
> Index: linux-2.6/fs/xfs/xfs_fsops.c
> ===================================================================
> --- linux-2.6.orig/fs/xfs/xfs_fsops.c	2009-07-10 13:05:24.798364926  
> +0200
> +++ linux-2.6/fs/xfs/xfs_fsops.c	2009-07-10 13:16:00.827394975 +0200
> @@ -167,17 +167,25 @@ xfs_growfs_data_private(
> 	new = nb - mp->m_sb.sb_dblocks;
> 	oagcount = mp->m_sb.sb_agcount;
> 	if (nagcount > oagcount) {
> +		void *new_perag, *old_perag;
> +
> 		xfs_filestream_flush(mp);
> +
> +		new_perag = kmem_zalloc(sizeof(xfs_perag_t) * nagcount,
> +					KM_MAYFAIL);
> +		if (!new_perag)
> +			return XFS_ERROR(ENOMEM);
> +
> 		down_write(&mp->m_peraglock);
> -		mp->m_perag = kmem_realloc(mp->m_perag,
> -			sizeof(xfs_perag_t) * nagcount,
> -			sizeof(xfs_perag_t) * oagcount,
> -			KM_SLEEP);
> -		memset(&mp->m_perag[oagcount], 0,
> -			(nagcount - oagcount) * sizeof(xfs_perag_t));
> +		memcpy(new_perag, mp->m_perag, sizeof(xfs_perag_t) * oagcount);
> +		old_perag = mp->m_perag;
> +		mp->m_perag = new_perag;
> +
> 		mp->m_flags |= XFS_MOUNT_32BITINODES;
> 		nagimax = xfs_initialize_perag(mp, nagcount);
> 		up_write(&mp->m_peraglock);
> +
> +		kmem_free(old_perag);
> 	}
> 	tp = xfs_trans_alloc(mp, XFS_TRANS_GROWFS);
> 	tp->t_flags |= XFS_TRANS_RESERVE;
>
> _______________________________________________
> xfs mailing list
> xfs at oss.sgi.com
> http://oss.sgi.com/mailman/listinfo/xfs