linux-kernel - [PATCH] afs: Use a pagevec in afs

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Date:   Mon, 24 Aug 2020 19:34:24 +0100
From:   "Matthew Wilcox (Oracle)" <willy@...radead.org>
To:     David Howells <dhowells@...hat.com>
Cc:     "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        linux-afs@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH] afs: Use a pagevec in afs_writepages()

This amortises the overhead of retrieving pages from the pagecache
and the overhead of freeing pages if we happen to end up with the
last references to the pages.

Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
---
 fs/afs/write.c | 41 ++++++++++++++++++++++++-----------------
 1 file changed, 24 insertions(+), 17 deletions(-)

diff --git a/fs/afs/write.c b/fs/afs/write.c
index a121c247d95a..2d20037c7ff0 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -673,16 +673,24 @@ static int afs_writepages_region(struct address_space *mapping,
 				 struct writeback_control *wbc,
 				 pgoff_t index, pgoff_t end, pgoff_t *_next)
 {
-	struct page *page;
-	int ret, n;
+	struct pagevec pvec;
+	int ret, i = 0;
 
 	_enter(",,%lx,%lx,", index, end);
 
+	pagevec_init(&pvec);
 	do {
-		n = find_get_pages_range_tag(mapping, &index, end,
-					PAGECACHE_TAG_DIRTY, 1, &page);
-		if (!n)
-			break;
+		struct page *page;
+
+		if (i == pagevec_count(&pvec)) {
+			pagevec_release(&pvec);
+			if (!pagevec_lookup_range_tag(&pvec, mapping,
+					&index, end, PAGECACHE_TAG_DIRTY))
+				break;
+			i = 0;
+		}
+
+		page = pvec.pages[i++];
 
 		_debug("wback %lx", page->index);
 
@@ -693,15 +701,11 @@ static int afs_writepages_region(struct address_space *mapping,
 		 * back from swapper_space to tmpfs file mapping
 		 */
 		ret = lock_page_killable(page);
-		if (ret < 0) {
-			put_page(page);
-			_leave(" = %d", ret);
-			return ret;
-		}
+		if (ret < 0)
+			goto err;
 
 		if (page->mapping != mapping || !PageDirty(page)) {
 			unlock_page(page);
-			put_page(page);
 			continue;
 		}
 
@@ -709,7 +713,6 @@ static int afs_writepages_region(struct address_space *mapping,
 			unlock_page(page);
 			if (wbc->sync_mode != WB_SYNC_NONE)
 				wait_on_page_writeback(page);
-			put_page(page);
 			continue;
 		}
 
@@ -717,19 +720,23 @@ static int afs_writepages_region(struct address_space *mapping,
 			BUG();
 		ret = afs_write_back_from_locked_page(mapping, wbc, page, end);
 		put_page(page);
-		if (ret < 0) {
-			_leave(" = %d", ret);
-			return ret;
-		}
+		if (ret < 0)
+			goto err;
 
 		wbc->nr_to_write -= ret;
 
 		cond_resched();
 	} while (index < end && wbc->nr_to_write > 0);
 
+	pagevec_release(&pvec);
 	*_next = index;
 	_leave(" = 0 [%lx]", *_next);
 	return 0;
+
+err:
+	pagevec_release(&pvec);
+	_leave(" = %d", ret);
+	return ret;
 }
 
 /*
-- 
2.28.0