[PATCH-RESEND 4/4] pnfsblock: do not ask for layout in pg_init

[Peng Tao <bergwolf@gmail.com>]

Asking for layout in pg_init will always make client ask for only 4KB
layout in every layoutget. This way, client drops the IO size information
that is meaningful for MDS in handing out layout.

In stead, if layout is not find in cache, do not send layoutget
at once. Wait until before issuing IO in pnfs_do_multiple_reads/writes
because that is where we know the real size of current IO. By telling the
real IO size to MDS, MDS will have a better chance to give proper layout.

Signed-off-by: Peng Tao <peng_tao@emc.com>
---
Resend to fix patch title. Sorry for the noise...

 fs/nfs/blocklayout/blocklayout.c |   54 ++++++++++++++++++++++++++++++++++++-
 1 files changed, 52 insertions(+), 2 deletions(-)

diff --git a/fs/nfs/blocklayout/blocklayout.c b/fs/nfs/blocklayout/blocklayout.c
index 48cfac3..fd585fe 100644
--- a/fs/nfs/blocklayout/blocklayout.c
+++ b/fs/nfs/blocklayout/blocklayout.c
@@ -39,6 +39,7 @@
 #include <linux/prefetch.h>
 
 #include "blocklayout.h"
+#include "../internal.h"
 
 #define NFSDBG_FACILITY	NFSDBG_PNFS_LD
 
@@ -990,14 +991,63 @@ bl_clear_layoutdriver(struct nfs_server *server)
 	return 0;
 }
 
+/* While RFC doesn't limit maximum size of layout, we better limit it ourself. */
+#define PNFSBLK_MAXRSIZE (0x1<<22)
+#define PNFSBLK_MAXWSIZE (0x1<<21)
+static void
+bl_pg_init_read(struct nfs_pageio_descriptor *pgio, struct nfs_page *req)
+{
+	struct inode *ino = pgio->pg_inode;
+	struct pnfs_layout_hdr *lo;
+
+	BUG_ON(pgio->pg_lseg != NULL);
+	spin_lock(&ino->i_lock);
+	lo = pnfs_find_alloc_layout(ino, req->wb_context, GFP_KERNEL);
+	if (!lo || test_bit(lo_fail_bit(IOMODE_READ), &lo->plh_flags)) {
+		spin_unlock(&ino->i_lock);
+		nfs_pageio_reset_read_mds(pgio);
+		return;
+	}
+
+	pgio->pg_bsize = PNFSBLK_MAXRSIZE;
+	pgio->pg_lseg = pnfs_find_get_layout_locked(ino,
+						req_offset(req),
+						req->wb_bytes,
+						IOMODE_READ);
+	spin_unlock(&ino->i_lock);
+}
+
+static void
+bl_pg_init_write(struct nfs_pageio_descriptor *pgio, struct nfs_page *req)
+{
+	struct inode *ino = pgio->pg_inode;
+	struct pnfs_layout_hdr *lo;
+
+	BUG_ON(pgio->pg_lseg != NULL);
+	spin_lock(&ino->i_lock);
+	lo = pnfs_find_alloc_layout(ino, req->wb_context, GFP_NOFS);
+	if (!lo || test_bit(lo_fail_bit(IOMODE_RW), &lo->plh_flags)) {
+		spin_unlock(&ino->i_lock);
+		nfs_pageio_reset_write_mds(pgio);
+		return;
+	}
+
+	pgio->pg_bsize = PNFSBLK_MAXWSIZE;
+	pgio->pg_lseg = pnfs_find_get_layout_locked(ino,
+						req_offset(req),
+						req->wb_bytes,
+						IOMODE_RW);
+	spin_unlock(&ino->i_lock);
+}
+
 static const struct nfs_pageio_ops bl_pg_read_ops = {
-	.pg_init = pnfs_generic_pg_init_read,
+	.pg_init = bl_pg_init_read,
 	.pg_test = pnfs_generic_pg_test,
 	.pg_doio = pnfs_generic_pg_readpages,
 };
 
 static const struct nfs_pageio_ops bl_pg_write_ops = {
-	.pg_init = pnfs_generic_pg_init_write,
+	.pg_init = bl_pg_init_write,
 	.pg_test = pnfs_generic_pg_test,
 	.pg_doio = pnfs_generic_pg_writepages,
 };
-- 
1.7.1.262.g5ef3d