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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: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
This commit is contained in:
Trond Myklebust 2021-02-08 08:55:46 -05:00 committed by Anna Schumaker
parent 37eaeed1a5
commit fc9dc40189
2 changed files with 13 additions and 11 deletions
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4
fs/nfs/file.c
View File

@ -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);

20
fs/nfs/write.c
View File

@ -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;
}