linux-kernel - [PATCH v5 12/18] mm/filemap: Move the iocb checks into filemap_update

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Message-Id: <20210122160140.223228-13-willy@infradead.org>
Date:   Fri, 22 Jan 2021 16:01:34 +0000
From:   "Matthew Wilcox (Oracle)" <willy@...radead.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Kent Overstreet <kent.overstreet@...il.com>,
        Christoph Hellwig <hch@....de>
Subject: [PATCH v5 12/18] mm/filemap: Move the iocb checks into filemap_update_page

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) <willy@...radead.org>
Reviewed-by: Kent Overstreet <kent.overstreet@...il.com>
Reviewed-by: Christoph Hellwig <hch@....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