NFSv4.1: coelesce across layout stripes

Add a pg_test layout driver hook which is used to avoid coelescing I/O across
layout stripes.

Signed-off-by: Andy Adamson <andros@netapp.com>
Signed-off-by: Andy Adamson <andros@citi.umich.edu>
Signed-off-by: Dean Hildebrand <dhildeb@us.ibm.com>
Signed-off-by: Fred Isaman <iisaman@citi.umich.edu>
Signed-off-by: Fred Isaman <iisaman@netapp.com>
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
Signed-off-by: Tao Guo <guotao@nrchpc.ac.cn>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 26 insertions, 0 deletions

diff --git a/fs/nfs/nfs4filelayout.c b/fs/nfs/nfs4filelayout.c
index 23f930caf1e2..0efe8cbd9e3c 100644
--- a/fs/nfs/nfs4filelayout.c
+++ b/fs/nfs/nfs4filelayout.c
@@ -252,6 +252,31 @@ filelayout_free_lseg(struct pnfs_layout_segment *lseg)
         _filelayout_free_lseg(fl);
 }
 
+/*
+ * filelayout_pg_test(). Called by nfs_can_coalesce_requests()
+ *
+ * return 1 :  coalesce page
+ * return 0 :  don't coalesce page
+ */
+int
+filelayout_pg_test(struct nfs_pageio_descriptor *pgio, struct nfs_page *prev,
+                   struct nfs_page *req)
+{
+        u64 p_stripe, r_stripe;
+        u32 stripe_unit;
+
+        if (!pgio->pg_lseg)
+                return 1;
+        p_stripe = (u64)prev->wb_index << PAGE_CACHE_SHIFT;
+        r_stripe = (u64)req->wb_index << PAGE_CACHE_SHIFT;
+        stripe_unit = FILELAYOUT_LSEG(pgio->pg_lseg)->stripe_unit;
+
+        do_div(p_stripe, stripe_unit);
+        do_div(r_stripe, stripe_unit);
+
+        return (p_stripe == r_stripe);
+}
+
 static struct pnfs_layoutdriver_type filelayout_type = {
         .id = LAYOUT_NFSV4_1_FILES,
         .name = "LAYOUT_NFSV4_1_FILES",
@@ -260,6 +285,7 @@ static struct pnfs_layoutdriver_type filelayout_type = {
         .clear_layoutdriver = filelayout_clear_layoutdriver,
         .alloc_lseg              = filelayout_alloc_lseg,
         .free_lseg               = filelayout_free_lseg,
+        .pg_test                = filelayout_pg_test,
 };
 
 static int __init nfs4filelayout_init(void)