[PATCH 11/17] mm/filemap: Add filemap_range_uptodate

["Matthew Wilcox (Oracle)" <willy@infradead.org>]

Move the complicated condition and the calculations out of
filemap_update_page() into its own function.
---
 mm/filemap.c | 49 +++++++++++++++++++++++++++++++++----------------
 1 file changed, 33 insertions(+), 16 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index 41b90243f4ee..81b569d818a3 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2228,11 +2228,39 @@ static int filemap_read_page(struct file *file, struct address_space *mapping,
 	return error;
 }
 
+static bool filemap_range_uptodate(struct kiocb *iocb,
+		struct address_space *mapping, struct iov_iter *iter,
+		struct page *page)
+{
+	loff_t pos;
+	int count;
+
+	if (PageUptodate(page))
+		return true;
+	/* pipes can't handle partially uptodate pages */
+	if (iov_iter_is_pipe(iter))
+		return false;
+	if (!mapping->a_ops->is_partially_uptodate)
+		return false;
+	if (mapping->host->i_blkbits >= (PAGE_SHIFT + thp_order(page)))
+		return false;
+
+	pos = (loff_t) page->index << PAGE_SHIFT;
+	if (pos > iocb->ki_pos) {
+		count = iocb->ki_pos + iter->count - pos;
+		pos = 0;
+	} else {
+		count = iter->count;
+		pos = iocb->ki_pos & (thp_size(page) - 1);
+	}
+
+	return mapping->a_ops->is_partially_uptodate(page, pos, count);
+}
+
 static int filemap_update_page(struct kiocb *iocb,
 		struct address_space *mapping, struct iov_iter *iter,
 		struct page *page, loff_t pos, loff_t count, bool first)
 {
-	struct inode *inode = mapping->host;
 	int error = -EAGAIN;
 
 	if (!trylock_page(page)) {
@@ -2252,22 +2280,11 @@ static int filemap_update_page(struct kiocb *iocb,
 
 	if (!page->mapping)
 		goto truncated;
-	if (PageUptodate(page))
-		goto uptodate;
-	if (inode->i_blkbits == PAGE_SHIFT ||
-			!mapping->a_ops->is_partially_uptodate)
-		goto readpage;
-	/* pipes can't handle partially uptodate pages */
-	if (unlikely(iov_iter_is_pipe(iter)))
-		goto readpage;
-	if (!mapping->a_ops->is_partially_uptodate(page,
-				pos & (thp_size(page) - 1), count))
-		goto readpage;
-uptodate:
-	unlock_page(page);
-	return 0;
+	if (filemap_range_uptodate(iocb, mapping, iter, page)) {
+		unlock_page(page);
+		return 0;
+	}
 
-readpage:
 	if (iocb->ki_flags & (IOCB_NOIO | IOCB_NOWAIT | IOCB_WAITQ)) {
 		unlock_page(page);
 		error = -EAGAIN;
-- 
2.28.0