Commit 8b1f9ee5 authored by Trond Myklebust's avatar Trond Myklebust
Browse files

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: default avatarTrond Myklebust <Trond.Myklebust@netapp.com>
parent 77f11192

fs/nfs/file.c

+14 −22
Original line number Diff line number Diff line
@@ -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;

}