On Thu, Aug 7, 2014 at 3:23 PM, Christoph Hellwig <hch@xxxxxx> wrote:
> The Linux VM subsystem can't support block sizes larger than page size
> for block based filesystems very well. While this can be hacked around
> to some extent for simple filesystems the read-modify-write cycles
> required for pnfs block invalid extents are extremly deadlock prone
> when operating on multiple pages. Reject this case early on instead
> of pretending to support it (badly).
>
So this kills EMC server support. Can you please share what kind of
badly deadlock you saw with large block size support?
Thanks,
Tao
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
> fs/nfs/blocklayout/blocklayout.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/fs/nfs/blocklayout/blocklayout.c b/fs/nfs/blocklayout/blocklayout.c
> index cbb1797..6c1a421 100644
> --- a/fs/nfs/blocklayout/blocklayout.c
> +++ b/fs/nfs/blocklayout/blocklayout.c
> @@ -1115,6 +1115,12 @@ bl_set_layoutdriver(struct nfs_server *server, const struct nfs_fh *fh)
> dprintk("%s Server did not return blksize\n", __func__);
> return -EINVAL;
> }
> + if (server->pnfs_blksize > PAGE_SIZE) {
> + printk(KERN_ERR "%s: pNFS blksize %d not supported.\n",
> + __func__, server->pnfs_blksize);
> + return -EINVAL;
> + }
> +
> b_mt_id = kzalloc(sizeof(struct block_mount_id), GFP_NOFS);
> if (!b_mt_id) {
> status = -ENOMEM;
> --
> 1.9.1
>
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