[pnfs] [PATCH 01/25] pnfs: fix pnfs_{read|write}pages

[Fred Isaman]

THIS WILL BREAK OTHER LAYOUT DRIVERS that rely on old behavior.

This patch fixes two basic problems:
1. It is impossible to fall back to nfs from the layout driver's
read_pagelist or write_pagelist routines.
2. The pnfs.c code is assuming that if these routines return a non-zero
status, that pnfs_writeback_done (or pnfs_read_done) was not called, which
is not consistent with them returning count of bytes read/written.

This patch alters the call chain, and expects
ld_io_ops->{read|write}_pagelist to return either a 0 or 1, consistent
with its parents, putting any other information that needs to be returned
into the data.res and data.task structures.

Signed-off-by: Fred Isaman <iisaman at citi.umich.edu>
---
 fs/nfs/pnfs.c             |   31 ++++++++++++++++++++++---------
 include/linux/nfs4_pnfs.h |   10 ++++++++--
 2 files changed, 30 insertions(+), 11 deletions(-)

diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
index 3f34f34..5e12cd1 100644
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -1364,6 +1364,11 @@ pnfs_writepages(struct nfs_write_data *wdata, int how)
 	if (pnfs_get_type(inode) != LAYOUT_NFSV4_FILES)
 		wdata->pnfsflags |= PNFS_NO_RPC;
 	wdata->lseg = lseg;
+	/* FRED - this should return just 0 (to indicate done for now)
+	 * or 1 (to indicate try normal nfs).  It can indicate bytes
+	 * written in wdata->res.count.  It can indicate error status in
+	 * wdata->task.tk_status.
+	 */
 	status = nfss->pnfs_curr_ld->ld_io_ops->write_pagelist(
 							nfsi->current_layout,
 							args->pages,
@@ -1374,13 +1379,15 @@ pnfs_writepages(struct nfs_write_data *wdata, int how)
 							how,
 							wdata);
 
-	if (status)
+	if (status) {
 		put_lseg(lseg);
-	if (status > 0) {
-		dprintk("%s: LD write_pagelist returned status %d > 0\n", __FUNCTION__, status);
-		pnfs_update_last_write(nfsi, args->offset, status);
+		wdata->pnfsflags &= ~PNFS_NO_RPC;
+	}
+	if (status == 0 && wdata->res.count > 0) {
+		dprintk("%s: LD write_pagelist returned count %d > 0\n",
+			__FUNCTION__, wdata->res.count);
+		pnfs_update_last_write(nfsi, args->offset, wdata->res.count);
 		pnfs_need_layoutcommit(nfsi, wdata->args.context);
-		status = 0;
 	}
 
 out:
@@ -1447,6 +1454,11 @@ pnfs_readpages(struct nfs_read_data *rdata)
 	if (pnfs_get_type(inode) != LAYOUT_NFSV4_FILES)
 		rdata->pnfsflags |= PNFS_NO_RPC;
 	rdata->lseg = lseg;
+	/* FRED - this should return just 0 (to indicate done for now)
+	 * or 1 (to indicate try normal nfs).  It can indicate bytes
+	 * read in rdata->res.count.  It can indicate error status in
+	 * rdata->task.tk_status.
+	 */
 	status = nfss->pnfs_curr_ld->ld_io_ops->read_pagelist(
 							nfsi->current_layout,
 							args->pages,
@@ -1455,12 +1467,13 @@ pnfs_readpages(struct nfs_read_data *rdata)
 							(loff_t)args->offset,
 							args->count,
 							rdata);
-	if (status)
+	if (status) {
 		put_lseg(lseg);
-	if (status > 0) {
-		dprintk("%s: LD read_pagelist returned status %d > 0\n", __FUNCTION__, status);
-		status = 0;
+		rdata->pnfsflags &= ~PNFS_NO_RPC;
 	}
+	if (status == 0 && rdata->res.count > 0)
+		dprintk("%s: LD read_pagelist returned count %d > 0\n",
+			__FUNCTION__, status);
 
  out:
 	dprintk("%s: End Status %d\n", __FUNCTION__, status);
diff --git a/include/linux/nfs4_pnfs.h b/include/linux/nfs4_pnfs.h
index 8a720e5..655f1f7 100644
--- a/include/linux/nfs4_pnfs.h
+++ b/include/linux/nfs4_pnfs.h
@@ -115,8 +115,14 @@ struct layoutdriver_io_operations {
 	/* Functions that use the pagecache.
 	 * If use_pagecache == 1, then these functions must be implemented.
 	 */
-	ssize_t (*read_pagelist) (struct pnfs_layout_type *layoutid, struct page **pages, unsigned int pgbase, unsigned nr_pages, loff_t offset, size_t count, struct nfs_read_data *nfs_data);
-	ssize_t (*write_pagelist) (struct pnfs_layout_type *layoutid, struct page **pages, unsigned int pgbase, unsigned nr_pages, loff_t offset, size_t count, int sync, struct nfs_write_data *nfs_data);
+	int (*read_pagelist) (struct pnfs_layout_type *layoutid,
+			      struct page **pages, unsigned int pgbase,
+			      unsigned nr_pages, loff_t offset, size_t count,
+			      struct nfs_read_data *nfs_data);
+	int (*write_pagelist) (struct pnfs_layout_type *layoutid,
+			       struct page **pages, unsigned int pgbase,
+			       unsigned nr_pages, loff_t offset, size_t count,
+			       int sync, struct nfs_write_data *nfs_data);
 	int (*flush_one) (struct inode *inode, struct list_head *head, unsigned int npages, size_t count, int how);
 	void (*free_request_data) (struct nfs_page *);
 
-- 
1.5.3.3