pNFS: Add tracking to limit the number of pNFS retries

When the client is reading or writing using pNFS, and hits an error
on the DS, then it typically sends a LAYOUTERROR and/or LAYOUTRETURN
to the MDS, before redirtying the failed pages, and going for a new
round of reads/writebacks. The problem is that if the server has no
way to fix the DS, then we may need a way to interrupt this loop
after a set number of attempts have been made.
This patch adds an optional module parameter that allows the admin
to specify how many times to retry the read/writeback process before
failing with a fatal error.
The default behaviour is to retry forever.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

1 files changed, 3 insertions, 1 deletions

diff --git a/include/linux/nfs_page.h b/include/linux/nfs_page.h
index b7d0f15615c2..8b36800d342d 100644
--- a/include/linux/nfs_page.h
+++ b/include/linux/nfs_page.h
@@ -53,6 +53,7 @@ struct nfs_page {
 	struct nfs_write_verifier	wb_verf;	/* Commit cookie */
 	struct nfs_page		*wb_this_page;  /* list of reqs for this page */
 	struct nfs_page		*wb_head;       /* head pointer for req list */
+	unsigned short		wb_nio;		/* Number of I/O attempts */
 };
 
 struct nfs_pageio_descriptor;
@@ -87,7 +88,6 @@ struct nfs_pgio_mirror {
 };
 
 struct nfs_pageio_descriptor {
-	unsigned char		pg_moreio : 1;
 	struct inode		*pg_inode;
 	const struct nfs_pageio_ops *pg_ops;
 	const struct nfs_rw_ops *pg_rw_ops;
@@ -105,6 +105,8 @@ struct nfs_pageio_descriptor {
 	struct nfs_pgio_mirror	pg_mirrors_static[1];
 	struct nfs_pgio_mirror	*pg_mirrors_dynamic;
 	u32			pg_mirror_idx;	/* current mirror */
+	unsigned short		pg_maxretrans;
+	unsigned char		pg_moreio : 1;
 };
 
 /* arbitrarily selected limit to number of mirrors */