[pnfs] [PATCH 7/7] nfs4_pnfs_layout_segment: layout driver has_layout method

[Benny Halevy]

declare and use a layout-driver has_layout method
that can optionally determine if the layout driver has the
layout for a given layout segment (iomode and byte range).

Layout drivers that maintain only a single layout per file
do not have to implement this method.

Use this method in virtual_update_layout to determine whether
LAYOUTGET is required or not.

Signed-off-by: Benny Halevy <bhalevy at panasas.com>
---
 fs/nfs/pnfs.c             |    5 ++++-
 include/linux/nfs4_pnfs.h |    1 +
 2 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
index aa7afa3..646db94 100644
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -462,7 +462,10 @@ virtual_update_layout(struct inode* ino,
 	arg.lseg.offset = pos;
 	arg.lseg.length = count;
 	/* Check to see if the layout for the given range already exists */
-	if (nfsi->current_layout != NULL) {
+	if (nfsi->current_layout != NULL &&
+            (!nfss->pnfs_curr_ld->ld_io_ops->has_layout ||
+             nfss->pnfs_curr_ld->ld_io_ops->has_layout(
+		nfsi->current_layout, ino, &arg.lseg))) {
 		/* TODO: To make this generic, I would need to compare the extents
 		 * of the existing layout information.
 		 * For now, assume that whole file layouts are always returned.
diff --git a/include/linux/nfs4_pnfs.h b/include/linux/nfs4_pnfs.h
index 964065d..493c842 100644
--- a/include/linux/nfs4_pnfs.h
+++ b/include/linux/nfs4_pnfs.h
@@ -62,6 +62,7 @@ struct layoutdriver_io_operations {
 	 * inode specific layout structure.  Each subsequent layoutget operation results in
 	 * a set_layout call to set the opaque layout in the layout driver.*/
 	struct pnfs_layout_type* (*alloc_layout) (struct pnfs_mount_type * mountid, struct inode * inode);
+	int (*has_layout) (struct pnfs_layout_type * layoutid, struct inode * inode, struct nfs4_pnfs_layout_segment *range);
 	void (*free_layout) (struct pnfs_layout_type * layoutid, struct inode * inode, struct nfs4_pnfs_layout_segment *range);
 	struct pnfs_layout_type* (*set_layout) (struct pnfs_layout_type * layoutid, struct inode * inode, struct nfs4_pnfs_layoutget_res *lgr);
 
-- 
1.5.2.5