[PATCH 04/13] mm: handle readahead in generic_file_buffered_read_pagenotuptodate

[Christoph Hellwig <hch@xxxxxx>]

Move the calculation of the per-page variables and the readahead handling
from the only caller into generic_file_buffered_read_pagenotuptodate,
which now becomes a routine to handle everything related to bringing
one page uptodate and thus is renamed to filemap_read_one_page.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
 mm/filemap.c | 63 +++++++++++++++++++++++-----------------------------
 1 file changed, 28 insertions(+), 35 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index bae5b905aa7bdc..5cdf8090d4e12c 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2217,13 +2217,26 @@ static int filemap_readpage(struct kiocb *iocb, struct page *page)
 	return error;
 }
 
-static int generic_file_buffered_read_pagenotuptodate(struct kiocb *iocb,
-		struct iov_iter *iter, struct page *page, loff_t pos,
-		loff_t count, bool first)
+static int filemap_make_page_uptodate(struct kiocb *iocb, struct iov_iter *iter,
+		struct page *page, pgoff_t pg_index, bool first)
 {
-	struct address_space *mapping = iocb->ki_filp->f_mapping;
+	struct file *file = iocb->ki_filp;
+	struct address_space *mapping = file->f_mapping;
+	loff_t last = iocb->ki_pos + iter->count;
+	pgoff_t last_index = (last + PAGE_SIZE - 1) >> PAGE_SHIFT;
+	loff_t pos = max(iocb->ki_pos, (loff_t)pg_index << PAGE_SHIFT);
 	int error = -EAGAIN;
 
+	if (PageReadahead(page)) {
+		if (iocb->ki_flags & IOCB_NOIO)
+			goto put_page;
+		page_cache_async_readahead(mapping, &file->f_ra, file, page,
+					   pg_index, last_index - pg_index);
+	}
+
+	if (PageUptodate(page))
+		return 0;
+
 	if (iocb->ki_flags & IOCB_NOWAIT)
 		goto put_page;
 
@@ -2255,8 +2268,8 @@ static int generic_file_buffered_read_pagenotuptodate(struct kiocb *iocb,
 	/* Did it get truncated before we got the lock? */
 	if (!page->mapping)
 		goto page_not_up_to_date_locked;
-	if (!mapping->a_ops->is_partially_uptodate(page,
-				pos & ~PAGE_MASK, count))
+	if (!mapping->a_ops->is_partially_uptodate(page, pos & ~PAGE_MASK,
+			last - pos))
 		goto page_not_up_to_date_locked;
 
 unlock_page:
@@ -2360,35 +2373,15 @@ static int generic_file_buffered_read_get_pages(struct kiocb *iocb,
 		nr_got = 1;
 got_pages:
 	for (i = 0; i < nr_got; i++) {
-		struct page *page = pages[i];
-		pgoff_t pg_index = index + i;
-		loff_t pg_pos = max(iocb->ki_pos,
-				    (loff_t) pg_index << PAGE_SHIFT);
-		loff_t pg_count = iocb->ki_pos + iter->count - pg_pos;
-
-		if (PageReadahead(page)) {
-			if (iocb->ki_flags & IOCB_NOIO) {
-				for (j = i; j < nr_got; j++)
-					put_page(pages[j]);
-				nr_got = i;
-				err = -EAGAIN;
-				break;
-			}
-			page_cache_async_readahead(mapping, ra, filp, page,
-					pg_index, last_index - pg_index);
-		}
-
-		if (!PageUptodate(page)) {
-			err = generic_file_buffered_read_pagenotuptodate(iocb,
-					iter, page, pg_pos, pg_count, i == 0);
-			if (err) {
-				if (err == AOP_TRUNCATED_PAGE)
-					err = 0;
-				for (j = i + 1; j < nr_got; j++)
-					put_page(pages[j]);
-				nr_got = i;
-				break;
-			}
+		err = filemap_make_page_uptodate(iocb, iter, pages[i],
+				index + i, i == 0);
+		if (err) {
+			if (err == AOP_TRUNCATED_PAGE)
+				err = 0;
+			for (j = i + 1; j < nr_got; j++)
+				put_page(pages[j]);
+			nr_got = i;
+			break;
 		}
 	}
 
-- 
2.28.0