On Mon, Jul 10, 2023 at 02:02:53PM +0100, Matthew Wilcox (Oracle) wrote:
> If we have a large folio, we can copy in larger chunks than PAGE_SIZE.
> Start at the maximum page cache size and shrink by half every time we
> hit the "we are short on memory" problem.
>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
> Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Looks good!
Reviewed-by: Darrick J. Wong <djwong@xxxxxxxxxx>
--D
> ---
> fs/iomap/buffered-io.c | 32 +++++++++++++++++---------------
> 1 file changed, 17 insertions(+), 15 deletions(-)
>
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index 2d3e90f4d16e..f21f1f641c4a 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -769,6 +769,7 @@ static size_t iomap_write_end(struct iomap_iter *iter, loff_t pos, size_t len,
> static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
> {
> loff_t length = iomap_length(iter);
> + size_t chunk = PAGE_SIZE << MAX_PAGECACHE_ORDER;
> loff_t pos = iter->pos;
> ssize_t written = 0;
> long status = 0;
> @@ -777,15 +778,12 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
>
> do {
> struct folio *folio;
> - struct page *page;
> - unsigned long offset; /* Offset into pagecache page */
> - unsigned long bytes; /* Bytes to write to page */
> + size_t offset; /* Offset into folio */
> + size_t bytes; /* Bytes to write to folio */
> size_t copied; /* Bytes copied from user */
>
> - offset = offset_in_page(pos);
> - bytes = min_t(unsigned long, PAGE_SIZE - offset,
> - iov_iter_count(i));
> -again:
> + offset = pos & (chunk - 1);
> + bytes = min(chunk - offset, iov_iter_count(i));
> status = balance_dirty_pages_ratelimited_flags(mapping,
> bdp_flags);
> if (unlikely(status))
> @@ -815,12 +813,14 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
> if (iter->iomap.flags & IOMAP_F_STALE)
> break;
>
> - page = folio_file_page(folio, pos >> PAGE_SHIFT);
> - if (mapping_writably_mapped(mapping))
> - flush_dcache_page(page);
> + offset = offset_in_folio(folio, pos);
> + if (bytes > folio_size(folio) - offset)
> + bytes = folio_size(folio) - offset;
>
> - copied = copy_page_from_iter_atomic(page, offset, bytes, i);
> + if (mapping_writably_mapped(mapping))
> + flush_dcache_folio(folio);
>
> + copied = copy_folio_from_iter_atomic(folio, offset, bytes, i);
> status = iomap_write_end(iter, pos, bytes, copied, folio);
>
> if (unlikely(copied != status))
> @@ -836,11 +836,13 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
> */
> if (copied)
> bytes = copied;
> - goto again;
> + if (chunk > PAGE_SIZE)
> + chunk /= 2;
> + } else {
> + pos += status;
> + written += status;
> + length -= status;
> }
> - pos += status;
> - written += status;
> - length -= status;
> } while (iov_iter_count(i) && length);
>
> if (status == -EAGAIN) {
> --
> 2.39.2
>
