linux-kernel - [PATCH v11 04/25] mm: Move readahead nr_pages check into read

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Date:   Tue, 14 Apr 2020 08:02:12 -0700
From:   Matthew Wilcox <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, linux-btrfs@...r.kernel.org,
        linux-erofs@...ts.ozlabs.org, linux-ext4@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net, cluster-devel@...hat.com,
        ocfs2-devel@....oracle.com, linux-xfs@...r.kernel.org,
        Zi Yan <ziy@...dia.com>, John Hubbard <jhubbard@...dia.com>,
        Christoph Hellwig <hch@....de>,
        William Kucharski <william.kucharski@...cle.com>
Subject: [PATCH v11 04/25] mm: Move readahead nr_pages check into read_pages

From: "Matthew Wilcox (Oracle)" <willy@...radead.org>

Simplify the callers by moving the check for nr_pages and the BUG_ON
into read_pages().

Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
Reviewed-by: Zi Yan <ziy@...dia.com>
Reviewed-by: John Hubbard <jhubbard@...dia.com>
Reviewed-by: Christoph Hellwig <hch@....de>
Reviewed-by: William Kucharski <william.kucharski@...cle.com>
---
 mm/readahead.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/mm/readahead.c b/mm/readahead.c
index 61b15b6b9e72..9fcd4e32b62d 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -119,6 +119,9 @@ static void read_pages(struct address_space *mapping, struct file *filp,
 	struct blk_plug plug;
 	unsigned page_idx;
 
+	if (!nr_pages)
+		return;
+
 	blk_start_plug(&plug);
 
 	if (mapping->a_ops->readpages) {
@@ -138,6 +141,8 @@ static void read_pages(struct address_space *mapping, struct file *filp,
 
 out:
 	blk_finish_plug(&plug);
+
+	BUG_ON(!list_empty(pages));
 }
 
 /*
@@ -180,8 +185,7 @@ void __do_page_cache_readahead(struct address_space *mapping,
 			 * contiguous pages before continuing with the next
 			 * batch.
 			 */
-			if (nr_pages)
-				read_pages(mapping, filp, &page_pool, nr_pages,
+			read_pages(mapping, filp, &page_pool, nr_pages,
 						gfp_mask);
 			nr_pages = 0;
 			continue;
@@ -202,9 +206,7 @@ void __do_page_cache_readahead(struct address_space *mapping,
 	 * uptodate then the caller will launch readpage again, and
 	 * will then handle the error.
 	 */
-	if (nr_pages)
-		read_pages(mapping, filp, &page_pool, nr_pages, gfp_mask);
-	BUG_ON(!list_empty(&page_pool));
+	read_pages(mapping, filp, &page_pool, nr_pages, gfp_mask);
 }
 
 /*
-- 
2.25.1