[PATCH] NFS: Write optimization for short files and small O_SYNC writes.

 Use stable writes if we can see that we are only going to put a single
 write on the wire.

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

1 files changed, 11 insertions, 3 deletions

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index c574d551f029..79b621a545b2 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -750,7 +750,7 @@ int nfs_updatepage(struct file *file, struct page *page,
          * is entirely in cache, it may be more efficient to avoid
          * fragmenting write requests.
          */
-        if (PageUptodate(page) && inode->i_flock == NULL) {
+        if (PageUptodate(page) && inode->i_flock == NULL && !(file->f_mode & O_SYNC)) {
                 loff_t end_offs = i_size_read(inode) - 1;
                 unsigned long end_index = end_offs >> PAGE_CACHE_SHIFT;
 
@@ -1342,8 +1342,16 @@ static int nfs_flush_inode(struct inode *inode, unsigned long idx_start,
         spin_lock(&nfsi->req_lock);
         res = nfs_scan_dirty(inode, &head, idx_start, npages);
         spin_unlock(&nfsi->req_lock);
-        if (res)
-                error = nfs_flush_list(&head, NFS_SERVER(inode)->wpages, how);
+        if (res) {
+                struct nfs_server *server = NFS_SERVER(inode);
+
+                /* For single writes, FLUSH_STABLE is more efficient */
+                if (res == nfsi->npages && nfsi->npages <= server->wpages) {
+                        if (res > 1 || nfs_list_entry(head.next)->wb_bytes <= server->wsize)
+                                how |= FLUSH_STABLE;
+                }
+                error = nfs_flush_list(&head, server->wpages, how);
+        }
         if (error < 0)
                 return error;
         return res;