linux-kernel - [PATCH v2 1/3] fs: remove redundant cache invalidation after async direct-io write

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Date:   Sat, 02 Nov 2019 16:12:58 +0300
From:   Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
To:     linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org
Cc:     linux-fsdevel@...r.kernel.org, Jens Axboe <axboe@...nel.dk>,
        Jan Kara <jack@...e.cz>,
        Alexander Viro <viro@...iv.linux.org.uk>
Subject: [PATCH v2 1/3] fs: remove redundant cache invalidation after async
 direct-io write

Function generic_file_direct_write() invalidates cache at entry. Second
time this should be done when request completes. But this function calls
second invalidation at exit unconditionally even for async requests.

This patch skips second invalidation for async requests (-EIOCBQUEUED).

Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
---
 mm/filemap.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index 85b7d087eb45..288e38199068 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -3218,9 +3218,11 @@ generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from)
 	 * Most of the time we do not need this since dio_complete() will do
 	 * the invalidation for us. However there are some file systems that
 	 * do not end up with dio_complete() being called, so let's not break
-	 * them by removing it completely
+	 * them by removing it completely.
+	 *
+	 * Skip invalidation for async writes or if mapping has no pages.
 	 */
-	if (mapping->nrpages)
+	if (written > 0 && mapping->nrpages)
 		invalidate_inode_pages2_range(mapping,
 					pos >> PAGE_SHIFT, end);