[pnfs] [PATCH 22/37] pnfs: client layout cache: introduce pnfs_layout_segment

[Benny Halevy]

struct pnfs_layout_segment is used to cache layout metadata
for a specific byte range and iomode.  It is allocated, referenced
by and passed down to the layout driver by the generic pnfs client layer.

new layoutdriver_io_operations.{alloc,free}_lseg methods are used
to allocate/set and free a layout segment.

Signed-off-by: Benny Halevy <bhalevy at panasas.com>
---
 include/linux/nfs4_pnfs.h |   16 ++++++++++++++++
 1 files changed, 16 insertions(+), 0 deletions(-)

diff --git a/include/linux/nfs4_pnfs.h b/include/linux/nfs4_pnfs.h
index 7ea5c33..f59e6c2 100644
--- a/include/linux/nfs4_pnfs.h
+++ b/include/linux/nfs4_pnfs.h
@@ -91,6 +91,20 @@ PNFS_LD_POLICY_OPS(struct pnfs_layout_type *lo)
 	return PNFS_LD(lo)->ld_policy_ops;
 }
 
+struct pnfs_layout_segment {
+	struct list_head fi_list;
+	struct nfs4_pnfs_layout_segment range;
+	struct kref kref;
+	struct pnfs_layout_type *layout;
+	u8 ld_data[];			/* layout driver private data */
+};
+
+static inline void *
+LSEG_LD_DATA(struct pnfs_layout_segment *lseg)
+{
+	return lseg->ld_data;
+}
+
 /* Layout driver I/O operations.
  * Either the pagecache or non-pagecache read/write operations must be implemented
  */
@@ -115,6 +129,8 @@ struct layoutdriver_io_operations {
 	int (*has_layout) (struct pnfs_layout_type *layoutid, struct inode *inode, struct nfs4_pnfs_layout_segment *range);
 	void (*free_layout) (struct pnfs_layout_type **layoutidp, struct nfs4_pnfs_layout_segment *range);
 	struct pnfs_layout_type * (*set_layout) (struct pnfs_layout_type *layoutid, struct nfs4_pnfs_layoutget_res *lgr);
+	struct pnfs_layout_segment * (*alloc_lseg) (struct pnfs_layout_type *layoutid, struct nfs4_pnfs_layoutget_res *lgr);
+	void (*free_lseg) (struct pnfs_layout_type *layoutid, struct pnfs_layout_segment *lseg);
 
 	int (*setup_layoutcommit) (struct pnfs_layout_type *layoutid, struct pnfs_layoutcommit_arg *arg);
 	void (*cleanup_layoutcommit) (struct pnfs_layout_type *layoutid, struct pnfs_layoutcommit_arg *arg, struct pnfs_layoutcommit_res *res);
-- 
1.5.3.3