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SubjectRe: [PATCH v2 19/28] iomap: Convert __iomap_zero_iter to use a folio
On Thu, Dec 09, 2021 at 09:38:03PM +0000, Matthew Wilcox wrote:
> @@ -891,16 +893,19 @@ static s64 __iomap_zero_iter(struct iomap_iter *iter, loff
> _t pos, u64 length)
> struct page *page;
> 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);
> + if (length > UINT_MAX)
> + length = UINT_MAX;
> + status = iomap_write_begin(iter, pos, length, &page);
> if (status)
> return status;
> + if (length > PAGE_SIZE - offset)
> + length = PAGE_SIZE - offset;
>
> - zero_user(page, offset, bytes);
> + zero_user(page, offset, length);
> mark_page_accessed(page);
>
> - return iomap_write_end(iter, pos, bytes, bytes, page);
> + return iomap_write_end(iter, pos, length, length, page);
> }

After attempting the merge with Christoph's ill-timed refactoring,
I decided that eliding the use of 'bytes' here was the wrong approach,
because it very much needs to be put back in for the merge.

Here's the merge as I have it:

diff --cc fs/iomap/buffered-io.c
index f3176cf90351,d1aa0f0e7fd5..40356db3e856
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@@ -888,19 -926,12 +904,23 @@@ static loff_t iomap_zero_iter(struct io
return length;

do {
- unsigned offset = offset_in_page(pos);
- size_t bytes = min_t(u64, PAGE_SIZE - offset, length);
- struct page *page;
- s64 bytes;
++ struct folio *folio;
+ int status;
++ size_t offset;
++ size_t bytes = min_t(u64, SIZE_MAX, 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);
++ offset = offset_in_folio(folio, pos);
++ if (bytes > folio_size(folio) - offset)
++ bytes = folio_size(folio) - offset;
++
++ folio_zero_range(folio, offset, bytes);
++ folio_mark_accessed(folio);
- bytes = iomap_write_end(iter, pos, bytes, bytes, page);
- if (IS_DAX(iter->inode))
- bytes = dax_iomap_zero(pos, length, iomap);
- else
- bytes = __iomap_zero_iter(iter, pos, length);
++ bytes = iomap_write_end(iter, pos, bytes, bytes, folio);
if (bytes < 0)
return bytes;
I've pushed out a new tag:

https://git.infradead.org/users/willy/linux.git/shortlog/refs/tags/iomap-folio-5.17d

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