[PATCH v5 12/18] mm/filemap: Move the iocb checks into filemap_update_page

[Matthew Wilcox (Oracle)]

We don't need to give up when a non-blocking request sees a !Uptodate page.
We may be able to satisfy the read from a partially-uptodate page.

Signed-off-by: Matthew Wilcox (Oracle) <wi...@infradead.org>
Reviewed-by: Kent Overstreet <kent.overstr...@gmail.com>
Reviewed-by: Christoph Hellwig <h...@lst.de>
---
 mm/filemap.c | 24 ++++++++++--------------
 1 file changed, 10 insertions(+), 14 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index 469fc97659cb5..9fbfb27483147 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2253,15 +2253,16 @@ static int filemap_update_page(struct kiocb *iocb,
        struct inode *inode = mapping->host;
        int error;
 
-       if (iocb->ki_flags & IOCB_WAITQ) {
-               error = lock_page_async(page, iocb->ki_waitq);
-               if (error)
-                       return error;
-       } else {
-               if (!trylock_page(page)) {
+       if (!trylock_page(page)) {
+               if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_NOIO))
+                       return -EAGAIN;
+               if (!(iocb->ki_flags & IOCB_WAITQ)) {
                        put_and_wait_on_page_locked(page, TASK_KILLABLE);
                        return AOP_TRUNCATED_PAGE;
                }
+               error = __lock_page_async(page, iocb->ki_waitq);
+               if (error)
+                       return error;
        }
 
        if (!page->mapping)
@@ -2379,14 +2380,9 @@ static int filemap_get_pages(struct kiocb *iocb, struct 
iov_iter *iter,
                }
 
                if (!PageUptodate(page)) {
-                       if ((iocb->ki_flags & IOCB_NOWAIT) ||
-                           ((iocb->ki_flags & IOCB_WAITQ) && pvec->nr > 1)) {
-                               put_page(page);
-                               pvec->nr--;
-                               err = -EAGAIN;
-                               goto err;
-                       }
-
+                       if ((iocb->ki_flags & IOCB_WAITQ) &&
+                           pagevec_count(pvec) > 1)
+                               iocb->ki_flags |= IOCB_NOWAIT;
                        err = filemap_update_page(iocb, mapping, iter, page,
                                        pg_pos, pg_count);
                        if (err) {
-- 
2.29.2