Re: [PATCH v14 098/138] iomap: Use folio offsets instead of page offsets

Darrick J. Wong
2021-07-15T21:27:02Z

On Thu, Jul 15, 2021 at 04:36:24AM +0100, Matthew Wilcox (Oracle) wrote:
> Pass a folio around instead of the page, and make sure the offset
> is relative to the start of the folio instead of the start of a page.
> Also use size_t for offset & length to make it clear that these are byte
> counts, and to support >2GB folios in the future.
>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> ---
> fs/iomap/buffered-io.c | 85 ++++++++++++++++++++++--------------------
> 1 file changed, 44 insertions(+), 41 deletions(-)
>
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index fbe4ebc074ce..707a96e36651 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -75,18 +75,18 @@ static void iomap_page_release(struct folio *folio)
> }
>
> /*
> - * Calculate the range inside the page that we actually need to read.
> + * Calculate the range inside the folio that we actually need to read.
> */
> -static void
> -iomap_adjust_read_range(struct inode *inode, struct iomap_page *iop,
> - loff_t *pos, loff_t length, unsigned *offp, unsigned *lenp)
> +static void iomap_adjust_read_range(struct inode *inode, struct folio *folio,
> + loff_t *pos, loff_t length, size_t *offp, size_t *lenp)
> {
> + struct iomap_page *iop = to_iomap_page(folio);
> loff_t orig_pos = *pos;
> loff_t isize = i_size_read(inode);
> unsigned block_bits = inode->i_blkbits;
> unsigned block_size = (1 << block_bits);
> - unsigned poff = offset_in_page(*pos);
> - unsigned plen = min_t(loff_t, PAGE_SIZE - poff, length);
> + size_t poff = offset_in_folio(folio, *pos);
> + size_t plen = min_t(loff_t, folio_size(folio) - poff, length);

I'm confused about 'size_t poff' here vs. 'unsigned end' later -- why do
we need a 64-bit quantity for poff? I suppose some day we might want to
have folios larger than 4GB or so, but so far we don't need that large
of a byte offset within a page/folio, right?

Or are you merely moving the codebase towards using size_t for all byte
offsets?

The rest of the conversion code looked ok though.

--D

> unsigned first = poff >> block_bits;
> unsigned last = (poff + plen - 1) >> block_bits;
>
> @@ -124,7 +124,7 @@ iomap_adjust_read_range(struct inode *inode, struct iomap_page *iop,
> * page cache for blocks that are entirely outside of i_size.
> */
> if (orig_pos <= isize && orig_pos + length > isize) {
> - unsigned end = offset_in_page(isize - 1) >> block_bits;
> + unsigned end = offset_in_folio(folio, isize - 1) >> block_bits;
>
> if (first <= end && last > end)
> plen -= (last - end) * block_size;
> @@ -134,31 +134,31 @@ iomap_adjust_read_range(struct inode *inode, struct iomap_page *iop,
> *lenp = plen;
> }
>
> -static void iomap_iop_set_range_uptodate(struct page *page,
> - struct iomap_page *iop, unsigned off, unsigned len)
> +static void iomap_iop_set_range_uptodate(struct folio *folio,
> + struct iomap_page *iop, size_t off, size_t len)
> {
> - struct inode *inode = page->mapping->host;
> + struct inode *inode = folio->mapping->host;
> unsigned first = off >> inode->i_blkbits;
> unsigned last = (off + len - 1) >> inode->i_blkbits;
> unsigned long flags;
>
> spin_lock_irqsave(&iop->uptodate_lock, flags);
> bitmap_set(iop->uptodate, first, last - first + 1);
> - if (bitmap_full(iop->uptodate, i_blocks_per_page(inode, page)))
> - SetPageUptodate(page);
> + if (bitmap_full(iop->uptodate, i_blocks_per_folio(inode, folio)))
> + folio_mark_uptodate(folio);
> spin_unlock_irqrestore(&iop->uptodate_lock, flags);
> }
>
> -static void iomap_set_range_uptodate(struct page *page,
> - struct iomap_page *iop, unsigned off, unsigned len)
> +static void iomap_set_range_uptodate(struct folio *folio,
> + struct iomap_page *iop, size_t off, size_t len)
> {
> - if (PageError(page))
> + if (folio_test_error(folio))
> return;
>
> if (iop)
> - iomap_iop_set_range_uptodate(page, iop, off, len);
> + iomap_iop_set_range_uptodate(folio, iop, off, len);
> else
> - SetPageUptodate(page);
> + folio_mark_uptodate(folio);
> }
>
> static void
> @@ -169,15 +169,17 @@ iomap_read_page_end_io(struct bio_vec *bvec, int error)
> struct iomap_page *iop = to_iomap_page(folio);
>
> if (unlikely(error)) {
> - ClearPageUptodate(page);
> - SetPageError(page);
> + folio_clear_uptodate(folio);
> + folio_set_error(folio);
> } else {
> - iomap_set_range_uptodate(page, iop, bvec->bv_offset,
> - bvec->bv_len);
> + size_t off = (page - &folio->page) * PAGE_SIZE +
> + bvec->bv_offset;
> +
> + iomap_set_range_uptodate(folio, iop, off, bvec->bv_len);
> }
>
> if (!iop || atomic_sub_and_test(bvec->bv_len, &iop->read_bytes_pending))
> - unlock_page(page);
> + folio_unlock(folio);
> }
>
> static void
> @@ -237,7 +239,7 @@ iomap_readpage_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
> struct iomap_page *iop = iomap_page_create(inode, folio);
> bool same_page = false, is_contig = false;
> loff_t orig_pos = pos;
> - unsigned poff, plen;
> + size_t poff, plen;
> sector_t sector;
>
> if (iomap->type == IOMAP_INLINE) {
> @@ -246,14 +248,14 @@ iomap_readpage_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
> return PAGE_SIZE;
> }
>
> - /* zero post-eof blocks as the page may be mapped */
> - iomap_adjust_read_range(inode, iop, &pos, length, &poff, &plen);
> + /* zero post-eof blocks as the folio may be mapped */
> + iomap_adjust_read_range(inode, folio, &pos, length, &poff, &plen);
> if (plen == 0)
> goto done;
>
> if (iomap_block_needs_zeroing(inode, iomap, pos)) {
> - zero_user(page, poff, plen);
> - iomap_set_range_uptodate(page, iop, poff, plen);
> + zero_user(&folio->page, poff, plen);
> + iomap_set_range_uptodate(folio, iop, poff, plen);
> goto done;
> }
>
> @@ -264,7 +266,7 @@ iomap_readpage_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
> /* Try to merge into a previous segment if we can */
> sector = iomap_sector(iomap, pos);
> if (ctx->bio && bio_end_sector(ctx->bio) == sector) {
> - if (__bio_try_merge_page(ctx->bio, page, plen, poff,
> + if (__bio_try_merge_page(ctx->bio, &folio->page, plen, poff,
> &same_page))
> goto done;
> is_contig = true;
> @@ -296,7 +298,7 @@ iomap_readpage_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
> ctx->bio->bi_end_io = iomap_read_end_io;
> }
>
> - bio_add_page(ctx->bio, page, plen, poff);
> + bio_add_folio(ctx->bio, folio, plen, poff);
> done:
> /*
> * Move the caller beyond our range so that it keeps making progress.
> @@ -531,9 +533,8 @@ iomap_write_failed(struct inode *inode, loff_t pos, unsigned len)
> truncate_pagecache_range(inode, max(pos, i_size), pos + len);
> }
>
> -static int
> -iomap_read_page_sync(loff_t block_start, struct page *page, unsigned poff,
> - unsigned plen, struct iomap *iomap)
> +static int iomap_read_folio_sync(loff_t block_start, struct folio *folio,
> + size_t poff, size_t plen, struct iomap *iomap)
> {
> struct bio_vec bvec;
> struct bio bio;
> @@ -542,7 +543,7 @@ iomap_read_page_sync(loff_t block_start, struct page *page, unsigned poff,
> bio.bi_opf = REQ_OP_READ;
> bio.bi_iter.bi_sector = iomap_sector(iomap, block_start);
> bio_set_dev(&bio, iomap->bdev);
> - __bio_add_page(&bio, page, plen, poff);
> + bio_add_folio(&bio, folio, plen, poff);
> return submit_bio_wait(&bio);
> }
>
> @@ -555,14 +556,15 @@ __iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, int flags,
> loff_t block_size = i_blocksize(inode);
> loff_t block_start = round_down(pos, block_size);
> loff_t block_end = round_up(pos + len, block_size);
> - unsigned from = offset_in_page(pos), to = from + len, poff, plen;
> + size_t from = offset_in_folio(folio, pos), to = from + len;
> + size_t poff, plen;
>
> - if (PageUptodate(page))
> + if (folio_test_uptodate(folio))
> return 0;
> - ClearPageError(page);
> + folio_clear_error(folio);
>
> do {
> - iomap_adjust_read_range(inode, iop, &block_start,
> + iomap_adjust_read_range(inode, folio, &block_start,
> block_end - block_start, &poff, &plen);
> if (plen == 0)
> break;
> @@ -575,14 +577,15 @@ __iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, int flags,
> if (iomap_block_needs_zeroing(inode, srcmap, block_start)) {
> if (WARN_ON_ONCE(flags & IOMAP_WRITE_F_UNSHARE))
> return -EIO;
> - zero_user_segments(page, poff, from, to, poff + plen);
> + zero_user_segments(&folio->page, poff, from, to,
> + poff + plen);
> } else {
> - int status = iomap_read_page_sync(block_start, page,
> + int status = iomap_read_folio_sync(block_start, folio,
> poff, plen, srcmap);
> if (status)
> return status;
> }
> - iomap_set_range_uptodate(page, iop, poff, plen);
> + iomap_set_range_uptodate(folio, iop, poff, plen);
> } while ((block_start += plen) < block_end);
>
> return 0;
> @@ -661,7 +664,7 @@ static size_t __iomap_write_end(struct inode *inode, loff_t pos, size_t len,
> */
> if (unlikely(copied < len && !PageUptodate(page)))
> return 0;
> - iomap_set_range_uptodate(page, iop, offset_in_page(pos), len);
> + iomap_set_range_uptodate(folio, iop, offset_in_folio(folio, pos), len);
> __set_page_dirty_nobuffers(page);
> return copied;
> }
> --
> 2.30.2
>