NFS: Writeback optimisation

Schedule writes using WB_SYNC_NONE first, then come back for a second pass
using WB_SYNC_ALL.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 22 insertions, 10 deletions

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index 75adb8e78db9..b3c5f5db73a4 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -1325,21 +1325,14 @@ long nfs_sync_mapping_wait(struct address_space *mapping, struct writeback_contr
         return ret;
 }
 
-static int nfs_write_mapping(struct address_space *mapping, int how)
+static int __nfs_write_mapping(struct address_space *mapping, struct writeback_control *wbc, int how)
 {
-        struct writeback_control wbc = {
-                .bdi = mapping->backing_dev_info,
-                .sync_mode = WB_SYNC_ALL,
-                .nr_to_write = LONG_MAX,
-                .for_writepages = 1,
-                .range_cyclic = 1,
-        };
         int ret;
 
-        ret = nfs_writepages(mapping, &wbc);
+        ret = nfs_writepages(mapping, wbc);
         if (ret < 0)
                 goto out;
-        ret = nfs_sync_mapping_wait(mapping, &wbc, how);
+        ret = nfs_sync_mapping_wait(mapping, wbc, how);
         if (ret < 0)
                 goto out;
         return 0;
@@ -1348,6 +1341,25 @@ out:
         return ret;
 }
 
+/* Two pass sync: first using WB_SYNC_NONE, then WB_SYNC_ALL */
+static int nfs_write_mapping(struct address_space *mapping, int how)
+{
+        struct writeback_control wbc = {
+                .bdi = mapping->backing_dev_info,
+                .sync_mode = WB_SYNC_NONE,
+                .nr_to_write = LONG_MAX,
+                .for_writepages = 1,
+                .range_cyclic = 1,
+        };
+        int ret;
+
+        ret = __nfs_write_mapping(mapping, &wbc, how);
+        if (ret < 0)
+                return ret;
+        wbc.sync_mode = WB_SYNC_ALL;
+        return __nfs_write_mapping(mapping, &wbc, how);
+}
+
 /*
  * flush the inode to disk.
  */