[pnfs] [PATCH 13/21] pnfsblock: allow use of PG_owner_priv_1 flag

[Fred Isaman]

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 at citi.umich.edu>
---
 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 fab9934..f804f02 100644
--- a/fs/nfs/blocklayout/blocklayout.h
+++ b/fs/nfs/blocklayout/blocklayout.h
@@ -37,6 +37,11 @@
 #include <linux/nfs4_pnfs.h>
 #include <linux/dm-ioctl.h> /* Needed for struct dm_ioctl*/
 
+#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)
+
 extern struct class shost_class; /* exported from drivers/scsi/hosts.c */
 extern int dm_dev_create(struct dm_ioctl *param); /* from dm-ioctl.c */
 extern int dm_dev_remove(struct dm_ioctl *param); /* from dm-ioctl.c */
-- 
1.5.3.3