Commit fc9dc401 authored by Trond Myklebust's avatar Trond Myklebust Committed by Anna Schumaker
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NFS: Optimise sparse writes past the end of file 



If we're doing a write, and the entire page lies beyond the end-of-file,
then we can assume the write can be extended to cover the beginning of
the page, since we know the data in that region will be all zeros.

Signed-off-by: default avatarTrond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: default avatarAnna Schumaker <Anna.Schumaker@Netapp.com>
parent 37eaeed1

fs/nfs/file.c

+1 −3
Original line number Diff line number Diff line
@@ -626,13 +626,11 @@ ssize_t nfs_file_write(struct kiocb *iocb, struct iov_iter *from) 
	/*

	 * O_APPEND implies that we must revalidate the file length.

	 */

	if (iocb->ki_flags & IOCB_APPEND) {

	if (iocb->ki_flags & IOCB_APPEND || iocb->ki_pos > i_size_read(inode)) {

		result = nfs_revalidate_file_size(inode, file);

		if (result)

			goto out;

	}

	if (iocb->ki_pos > i_size_read(inode))

		nfs_revalidate_mapping(inode, file->f_mapping);



	since = filemap_sample_wb_err(file->f_mapping);

	nfs_start_io_write(inode);

fs/nfs/write.c

+12 −8
Original line number Diff line number Diff line
@@ -1278,19 +1278,21 @@ bool nfs_ctx_key_to_expire(struct nfs_open_context *ctx, struct inode *inode) 
 * the PageUptodate() flag. In this case, we will need to turn off

 * write optimisations that depend on the page contents being correct.

 */

static bool nfs_write_pageuptodate(struct page *page, struct inode *inode)

static bool nfs_write_pageuptodate(struct page *page, struct inode *inode,

				   unsigned int pagelen)

{

	struct nfs_inode *nfsi = NFS_I(inode);



	if (nfs_have_delegated_attributes(inode))

		goto out;

	if (nfsi->cache_validity & NFS_INO_REVAL_PAGECACHE)

	if (nfsi->cache_validity &

	    (NFS_INO_REVAL_PAGECACHE | NFS_INO_INVALID_SIZE))

		return false;

	smp_rmb();

	if (test_bit(NFS_INO_INVALIDATING, &nfsi->flags))

	if (test_bit(NFS_INO_INVALIDATING, &nfsi->flags) && pagelen != 0)

		return false;

out:

	if (nfsi->cache_validity & NFS_INO_INVALID_DATA)

	if (nfsi->cache_validity & NFS_INO_INVALID_DATA && pagelen != 0)

		return false;

	return PageUptodate(page) != 0;

}
@@ -1310,7 +1312,8 @@ is_whole_file_wrlock(struct file_lock *fl) 
 * If the file is opened for synchronous writes then we can just skip the rest

 * of the checks.

 */

static int nfs_can_extend_write(struct file *file, struct page *page, struct inode *inode)

static int nfs_can_extend_write(struct file *file, struct page *page,

				struct inode *inode, unsigned int pagelen)

{

	int ret;

	struct file_lock_context *flctx = inode->i_flctx;
@@ -1318,7 +1321,7 @@ static int nfs_can_extend_write(struct file *file, struct page *page, struct ino 


	if (file->f_flags & O_DSYNC)

		return 0;

	if (!nfs_write_pageuptodate(page, inode))

	if (!nfs_write_pageuptodate(page, inode, pagelen))

		return 0;

	if (NFS_PROTO(inode)->have_delegation(inode, FMODE_WRITE))

		return 1;
@@ -1356,6 +1359,7 @@ int nfs_updatepage(struct file *file, struct page *page, 
	struct nfs_open_context *ctx = nfs_file_open_context(file);

	struct address_space *mapping = page_file_mapping(page);

	struct inode	*inode = mapping->host;

	unsigned int	pagelen = nfs_page_length(page);

	int		status = 0;



	nfs_inc_stats(inode, NFSIOS_VFSUPDATEPAGE);
@@ -1366,8 +1370,8 @@ int nfs_updatepage(struct file *file, struct page *page, 
	if (!count)

		goto out;



	if (nfs_can_extend_write(file, page, inode)) {

		count = max(count + offset, nfs_page_length(page));

	if (nfs_can_extend_write(file, page, inode, pagelen)) {

		count = max(count + offset, pagelen);

		offset = 0;

	}