Re: [PATCH 1/2] iomap: support tail packing inline read

On Fri, Jul 16, 2021 at 10:19:09AM +0100, Christoph Hellwig wrote:

 static void
 iomap_read_inline_data(struct inode *inode, struct page *page,
-		struct iomap *iomap)
+		struct iomap *iomap, loff_t pos, unsigned int size)
 {
-	size_t size = i_size_read(inode);
+	unsigned int block_aligned_size = round_up(size, i_blocksize(inode));
+	unsigned int poff = offset_in_page(pos);
 	void *addr;
 
-	if (PageUptodate(page))
-		return;
-
-	BUG_ON(page_has_private(page));
-	BUG_ON(page->index);
+	/* make sure that inline_data doesn't cross page boundary */
 	BUG_ON(size > PAGE_SIZE - offset_in_page(iomap->inline_data));
+	BUG_ON(size != i_size_read(inode) - pos);
 
 	addr = kmap_atomic(page);
-	memcpy(addr, iomap->inline_data, size);
-	memset(addr + size, 0, PAGE_SIZE - size);
+	memcpy(addr + poff, iomap->inline_data - iomap->offset + pos, size);
+	memset(addr + poff + size, 0, block_aligned_size - size);
 	kunmap_atomic(addr);
-	SetPageUptodate(page);
+
+	iomap_set_range_uptodate(page, poff, block_aligned_size);
 }

This should be relatively straightforward to port to folios.
I think it looks something like this ...

@@ -211,23 +211,18 @@ struct iomap_readpage_ctx {
 };

 static void iomap_read_inline_data(struct inode *inode, struct folio *folio,
-               struct iomap *iomap)
+               struct iomap *iomap, loff_t pos, size_t size)
 {
-       size_t size = i_size_read(inode);
        void *addr;
+       size_t offset = offset_in_folio(folio, pos);

-       if (folio_test_uptodate(folio))
-               return;
+       BUG_ON(size != i_size_read(inode) - pos);

-       BUG_ON(folio->index);
-       BUG_ON(folio_multi(folio));
-       BUG_ON(size > PAGE_SIZE - offset_in_page(iomap->inline_data));
-
-       addr = kmap_local_folio(folio, 0);
+       addr = kmap_local_folio(folio, offset);
        memcpy(addr, iomap->inline_data, size);
        memset(addr + size, 0, PAGE_SIZE - size);
        kunmap_local(addr);
-       folio_mark_uptodate(folio);
+       iomap_set_range_uptodate(folio, to_iomap_page(folio), pos, size);
 }

-	if (iomap->type == IOMAP_INLINE) {
-		WARN_ON_ONCE(pos);
-		iomap_read_inline_data(inode, page, iomap);
-		return PAGE_SIZE;
-	}
+	if (iomap->type == IOMAP_INLINE && !pos)
+		WARN_ON_ONCE(to_iomap_page(page) != NULL);
+	else
+		iop = iomap_page_create(inode, page);

This WARN_ON doesn't make sense to me.  If a file contains bytes 0-2047
that are !INLINE and then bytes 2048-2050 that are INLINE, we're going
to trigger it.  Perhaps just make this:

	if (iomap->type != IOMAP_INLINE || pos)
		iop = iomap_page_create(inode, page);