NFS: Optimise nfs_vm_page_mkwrite()

The current model locks the page twice for no good reason. Optimise by
inlining the parts of nfs_write_begin()/nfs_write_end() that we care about.

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

1 files changed, 14 insertions, 22 deletions

diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index b3bb89f7d5d2..4560fc2ddb4a 100644
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -392,35 +392,27 @@ static int nfs_vm_page_mkwrite(struct vm_area_struct *vma, struct page *page)
         struct file *filp = vma->vm_file;
         unsigned pagelen;
         int ret = -EINVAL;
-        void *fsdata;
         struct address_space *mapping;
-        loff_t offset;
 
         lock_page(page);
         mapping = page->mapping;
-        if (mapping != vma->vm_file->f_path.dentry->d_inode->i_mapping) {
-                unlock_page(page);
-                return -EINVAL;
-        }
+        if (mapping != vma->vm_file->f_path.dentry->d_inode->i_mapping)
+                goto out_unlock;
+
+        ret = 0;
         pagelen = nfs_page_length(page);
-        offset = (loff_t)page->index << PAGE_CACHE_SHIFT;
-        unlock_page(page);
+        if (pagelen == 0)
+                goto out_unlock;
 
-        /*
-         * we can use mapping after releasing the page lock, because:
-         * we hold mmap_sem on the fault path, which should pin the vma
-         * which should pin the file, which pins the dentry which should
-         * hold a reference on inode.
-         */
+        ret = nfs_flush_incompatible(filp, page);
+        if (ret != 0)
+                goto out_unlock;
 
-        if (pagelen) {
-                struct page *page2 = NULL;
-                ret = nfs_write_begin(filp, mapping, offset, pagelen,
-                                0, &page2, &fsdata);
-                if (!ret)
-                        ret = nfs_write_end(filp, mapping, offset, pagelen,
-                                        pagelen, page2, fsdata);
-        }
+        ret = nfs_updatepage(filp, page, 0, pagelen);
+        if (ret == 0)
+                ret = pagelen;
+out_unlock:
+        unlock_page(page);
         return ret;
 }