NFSv4.1: filelayout i/o helpers

Prepare for filelayout_read_pagelist with helper functions that find the correct
data server, filehandle, and offset.

Signed-off-by: Andy Adamson <andros@citi.umich.edu>
Signed-off-by: Dean Hildebrand <dhildeb@us.ibm.com>
Signed-off-by: Fred Isaman <iisaman@netapp.com>
Signed-off-by: Marc Eshel <eshel@almaden.ibm.com>
Signed-off-by: Mike Sager <sager@netapp.com>
Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
Signed-off-by: Tao Guo <guotao@nrchpc.ac.cn>
Signed-off-by: Tigran Mkrtchyan <tigran@anahit.desy.de>
Signed-off-by: Tigran Mkrtchyan <tigran.mkrtchyan@desy.de>
Signed-off-by: Andy Adamson <andros@netapp.com>
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 34 insertions, 0 deletions

diff --git a/fs/nfs/nfs4filelayout.c b/fs/nfs/nfs4filelayout.c
index 0efe8cbd9e3c..ed833705dcee 100644
--- a/fs/nfs/nfs4filelayout.c
+++ b/fs/nfs/nfs4filelayout.c
@@ -66,6 +66,40 @@ filelayout_clear_layoutdriver(struct nfs_server *nfss)
         return 0;
 }
 
+static loff_t
+filelayout_get_dense_offset(struct nfs4_filelayout_segment *flseg,
+                            loff_t offset)
+{
+        u32 stripe_width = flseg->stripe_unit * flseg->dsaddr->stripe_count;
+        u64 tmp;
+
+        offset -= flseg->pattern_offset;
+        tmp = offset;
+        do_div(tmp, stripe_width);
+
+        return tmp * flseg->stripe_unit + do_div(offset, flseg->stripe_unit);
+}
+
+/* This function is used by the layout driver to calculate the
+ * offset of the file on the dserver based on whether the
+ * layout type is STRIPE_DENSE or STRIPE_SPARSE
+ */
+static loff_t
+filelayout_get_dserver_offset(struct pnfs_layout_segment *lseg, loff_t offset)
+{
+        struct nfs4_filelayout_segment *flseg = FILELAYOUT_LSEG(lseg);
+
+        switch (flseg->stripe_type) {
+        case STRIPE_SPARSE:
+                return offset;
+
+        case STRIPE_DENSE:
+                return filelayout_get_dense_offset(flseg, offset);
+        }
+
+        BUG();
+}
+
 /*
  * filelayout_check_layout()
  *