iomap: Allow iomap_write_begin() to be called with the full length

In the future, we want write_begin to know the entire length of the
write so that it can choose to allocate large folios.  Pass the full
length in from __iomap_zero_iter() and limit it where necessary.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 8d7a67655b60957adc5d9db991f0eec1bbd4f296..b1ded5204d1c450fbf1b2370e2d5473d420a3274 100644 (file)
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -619,6 +619,9 @@ static int iomap_write_begin(const struct iomap_iter *iter, loff_t pos,
        if (fatal_signal_pending(current))
                return -EINTR;
 
+       if (!mapping_large_folio_support(iter->inode->i_mapping))
+               len = min_t(size_t, len, PAGE_SIZE - offset_in_page(pos));
+
        if (page_ops && page_ops->page_prepare) {
                status = page_ops->page_prepare(iter->inode, pos, len);
                if (status)
@@ -632,6 +635,8 @@ static int iomap_write_begin(const struct iomap_iter *iter, loff_t pos,
                goto out_no_page;
        }
        folio = page_folio(page);
+       if (pos + len > folio_pos(folio) + folio_size(folio))
+               len = folio_pos(folio) + folio_size(folio) - pos;
 
        if (srcmap->type == IOMAP_INLINE)
                status = iomap_write_begin_inline(iter, page);
@@ -891,11 +896,13 @@ 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);
+       unsigned bytes = min_t(u64, UINT_MAX, length);
 
        status = iomap_write_begin(iter, pos, bytes, &page);
        if (status)
                return status;
+       if (bytes > PAGE_SIZE - offset)
+               bytes = PAGE_SIZE - offset;
 
        zero_user(page, offset, bytes);
        mark_page_accessed(page);