Re: [PATCH 15/21] iomap: Convert iomap_write_begin and iomap_write_end to folios

Darrick J. Wong
2021-11-02T23:22:17Z

On Mon, Nov 01, 2021 at 08:39:23PM +0000, Matthew Wilcox (Oracle) wrote:
> These functions still only work in PAGE_SIZE chunks, but there are
> fewer conversions from tail to head pages as a result of this patch.
>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> ---
> fs/iomap/buffered-io.c | 67 ++++++++++++++++++++++--------------------
> 1 file changed, 35 insertions(+), 32 deletions(-)
>
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index b55d947867b1..6df8fdbb1951 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -539,9 +539,8 @@ static int iomap_read_folio_sync(loff_t block_start, struct folio *folio,
> }
>
> static int __iomap_write_begin(const struct iomap_iter *iter, loff_t pos,
> - unsigned len, struct page *page)
> + size_t len, struct folio *folio)
> {
> - struct folio *folio = page_folio(page);
> const struct iomap *srcmap = iomap_iter_srcmap(iter);
> struct iomap_page *iop = iomap_page_create(iter->inode, folio);
> loff_t block_size = i_blocksize(iter->inode);
> @@ -583,9 +582,8 @@ static int __iomap_write_begin(const struct iomap_iter *iter, loff_t pos,
> }
>
> static int iomap_write_begin_inline(const struct iomap_iter *iter,
> - struct page *page)
> + struct folio *folio)
> {
> - struct folio *folio = page_folio(page);
> int ret;
>
> /* needs more work for the tailpacking case; disable for now */
> @@ -598,11 +596,13 @@ static int iomap_write_begin_inline(const struct iomap_iter *iter,
> }
>
> static int iomap_write_begin(const struct iomap_iter *iter, loff_t pos,
> - unsigned len, struct page **pagep)
> + size_t len, struct folio **foliop)
> {
> const struct iomap_page_ops *page_ops = iter->iomap.page_ops;
> const struct iomap *srcmap = iomap_iter_srcmap(iter);
> + struct folio *folio;
> struct page *page;
> + unsigned fgp = FGP_LOCK | FGP_WRITE | FGP_CREAT | FGP_STABLE | FGP_NOFS;
> int status = 0;
>
> BUG_ON(pos + len > iter->iomap.offset + iter->iomap.length);
> @@ -618,29 +618,30 @@ static int iomap_write_begin(const struct iomap_iter *iter, loff_t pos,
> return status;
> }
>
> - page = grab_cache_page_write_begin(iter->inode->i_mapping,
> - pos >> PAGE_SHIFT, AOP_FLAG_NOFS);
> - if (!page) {
> + folio = __filemap_get_folio(iter->inode->i_mapping, pos >> PAGE_SHIFT,
> + fgp, mapping_gfp_mask(iter->inode->i_mapping));
> + if (!folio) {
> status = -ENOMEM;
> goto out_no_page;
> }
>
> + page = folio_file_page(folio, pos >> PAGE_SHIFT);

Isn't this only needed in the BUFFER_HEAD case?

--D

> if (srcmap->type == IOMAP_INLINE)
> - status = iomap_write_begin_inline(iter, page);
> + status = iomap_write_begin_inline(iter, folio);
> else if (srcmap->flags & IOMAP_F_BUFFER_HEAD)
> status = __block_write_begin_int(page, pos, len, NULL, srcmap);
> else
> - status = __iomap_write_begin(iter, pos, len, page);
> + status = __iomap_write_begin(iter, pos, len, folio);
>
> if (unlikely(status))
> goto out_unlock;
>
> - *pagep = page;
> + *foliop = folio;
> return 0;
>
> out_unlock:
> - unlock_page(page);
> - put_page(page);
> + folio_unlock(folio);
> + folio_put(folio);
> iomap_write_failed(iter->inode, pos, len);
>
> out_no_page:
> @@ -650,11 +651,10 @@ static int iomap_write_begin(const struct iomap_iter *iter, loff_t pos,
> }
>
> static size_t __iomap_write_end(struct inode *inode, loff_t pos, size_t len,
> - size_t copied, struct page *page)
> + size_t copied, struct folio *folio)
> {
> - struct folio *folio = page_folio(page);
> struct iomap_page *iop = to_iomap_page(folio);
> - flush_dcache_page(page);
> + flush_dcache_folio(folio);
>
> /*
> * The blocks that were entirely written will now be uptodate, so we
> @@ -667,10 +667,10 @@ static size_t __iomap_write_end(struct inode *inode, loff_t pos, size_t len,
> * non-uptodate page as a zero-length write, and force the caller to
> * redo the whole thing.
> */
> - if (unlikely(copied < len && !PageUptodate(page)))
> + if (unlikely(copied < len && !folio_test_uptodate(folio)))
> return 0;
> iomap_set_range_uptodate(folio, iop, offset_in_folio(folio, pos), len);
> - __set_page_dirty_nobuffers(page);
> + filemap_dirty_folio(inode->i_mapping, folio);
> return copied;
> }
>
> @@ -694,8 +694,9 @@ static size_t iomap_write_end_inline(const struct iomap_iter *iter,
>
> /* Returns the number of bytes copied. May be 0. Cannot be an errno. */
> static size_t iomap_write_end(struct iomap_iter *iter, loff_t pos, size_t len,
> - size_t copied, struct page *page)
> + size_t copied, struct folio *folio)
> {
> + struct page *page = folio_file_page(folio, pos >> PAGE_SHIFT);
> const struct iomap_page_ops *page_ops = iter->iomap.page_ops;
> const struct iomap *srcmap = iomap_iter_srcmap(iter);
> loff_t old_size = iter->inode->i_size;
> @@ -707,7 +708,7 @@ static size_t iomap_write_end(struct iomap_iter *iter, loff_t pos, size_t len,
> ret = block_write_end(NULL, iter->inode->i_mapping, pos, len,
> copied, page, NULL);
> } else {
> - ret = __iomap_write_end(iter->inode, pos, len, copied, page);
> + ret = __iomap_write_end(iter->inode, pos, len, copied, folio);
> }
>
> /*
> @@ -719,13 +720,13 @@ static size_t iomap_write_end(struct iomap_iter *iter, loff_t pos, size_t len,
> i_size_write(iter->inode, pos + ret);
> iter->iomap.flags |= IOMAP_F_SIZE_CHANGED;
> }
> - unlock_page(page);
> + folio_unlock(folio);
>
> if (old_size < pos)
> pagecache_isize_extended(iter->inode, old_size, pos);
> if (page_ops && page_ops->page_done)
> page_ops->page_done(iter->inode, pos, ret, page);
> - put_page(page);
> + folio_put(folio);
>
> if (ret < len)
> iomap_write_failed(iter->inode, pos, len);
> @@ -740,6 +741,7 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
> long status = 0;
>
> do {
> + struct folio *folio;
> struct page *page;
> unsigned long offset; /* Offset into pagecache page */
> unsigned long bytes; /* Bytes to write to page */
> @@ -763,16 +765,17 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
> break;
> }
>
> - status = iomap_write_begin(iter, pos, bytes, &page);
> + status = iomap_write_begin(iter, pos, bytes, &folio);
> if (unlikely(status))
> break;
>
> + page = folio_file_page(folio, pos >> PAGE_SHIFT);
> if (mapping_writably_mapped(iter->inode->i_mapping))
> flush_dcache_page(page);
>
> copied = copy_page_from_iter_atomic(page, offset, bytes, i);
>
> - status = iomap_write_end(iter, pos, bytes, copied, page);
> + status = iomap_write_end(iter, pos, bytes, copied, folio);
>
> if (unlikely(copied != status))
> iov_iter_revert(i, copied - status);
> @@ -838,13 +841,13 @@ static loff_t iomap_unshare_iter(struct iomap_iter *iter)
> do {
> unsigned long offset = offset_in_page(pos);
> unsigned long bytes = min_t(loff_t, PAGE_SIZE - offset, length);
> - struct page *page;
> + struct folio *folio;
>
> - status = iomap_write_begin(iter, pos, bytes, &page);
> + status = iomap_write_begin(iter, pos, bytes, &folio);
> if (unlikely(status))
> return status;
>
> - status = iomap_write_end(iter, pos, bytes, bytes, page);
> + status = iomap_write_end(iter, pos, bytes, bytes, folio);
> if (WARN_ON_ONCE(status == 0))
> return -EIO;
>
> @@ -880,19 +883,19 @@ EXPORT_SYMBOL_GPL(iomap_file_unshare);
>
> static s64 __iomap_zero_iter(struct iomap_iter *iter, loff_t pos, u64 length)
> {
> - struct page *page;
> + struct folio *folio;
> int status;
> unsigned offset = offset_in_page(pos);
> unsigned bytes = min_t(u64, PAGE_SIZE - offset, length);
>
> - status = iomap_write_begin(iter, pos, bytes, &page);
> + status = iomap_write_begin(iter, pos, bytes, &folio);
> if (status)
> return status;
>
> - zero_user(page, offset, bytes);
> - mark_page_accessed(page);
> + zero_user(folio_file_page(folio, pos >> PAGE_SHIFT), offset, bytes);
> + folio_mark_accessed(folio);
>
> - return iomap_write_end(iter, pos, bytes, bytes, page);
> + return iomap_write_end(iter, pos, bytes, bytes, folio);
> }
>
> static loff_t iomap_zero_iter(struct iomap_iter *iter, bool *did_zero)
> --
> 2.33.0
>