On Sun, Jun 12, 2011 at 7:44 PM, Jim Rees <rees@xxxxxxxxx> wrote:
> From: Fred Isaman <iisaman@xxxxxxxxxxxxxx>
>
> There is currently no good way for pnfs to communicate problems. For
> example - the linux read code first tries to do readahead through
> nfs_readpages. Failure there is ignored, and it will later call
> nfs_readpage. Failure there is also ignored, except that the lack of
> PG_uptodate is communicated back via -EIO.
>
> With pnfs, it would be useful to be able to communicate to
> nfs_readpage that direct disk IO failed on readahead, and that it
> should failover to using the MDS.
>
> Making the page flag PG_owner_priv_1 available as PG_pnfserr is one
> way to do so. (An alternative would be to embed this in the layout,
> but then pg_test can't easily access the info.)
>
> This may be better as generic pnfs code, in which case it should be
> put in pnfs.h, or even page-flags.h
>
> Signed-off-by: Fred Isaman <iisaman@xxxxxxxxxxxxxx>
> Signed-off-by: Benny Halevy <bhalevy@xxxxxxxxxxx>
> ---
The error handling has changed a bit since this was written. It is
currently very course grained for simplicity reasons.
Is there any reason you can't do similarly, and just use
NFS_LAYOUT_{RW|RO}_FAILED in lo->plh_flags?
Fred
> fs/nfs/blocklayout/blocklayout.h | 5 +++++
> 1 files changed, 5 insertions(+), 0 deletions(-)
>
> diff --git a/fs/nfs/blocklayout/blocklayout.h b/fs/nfs/blocklayout/blocklayout.h
> index 21fa21c..293f009 100644
> --- a/fs/nfs/blocklayout/blocklayout.h
> +++ b/fs/nfs/blocklayout/blocklayout.h
> @@ -35,6 +35,11 @@
> #include <linux/nfs_fs.h>
> #include "../pnfs.h"
>
> +#define PG_pnfserr PG_owner_priv_1
> +#define PagePnfsErr(page) test_bit(PG_pnfserr, &(page)->flags)
> +#define SetPagePnfsErr(page) set_bit(PG_pnfserr, &(page)->flags)
> +#define ClearPagePnfsErr(page) clear_bit(PG_pnfserr, &(page)->flags)
> +
> struct block_mount_id {
> spinlock_t bm_lock; /* protects list */
> struct list_head bm_devlist; /* holds pnfs_block_dev */
> --
> 1.7.4.1
>
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