[PATCH v2 3/3] fs: warn if stale pagecache is left after direct write

[Konstantin Khlebnikov]

Function generic_file_direct_write() tries to invalidate pagecache after
O_DIRECT write. Unlike to similar code in dio_complete() this silently
ignores error returned from invalidate_inode_pages2_range().

According to comment this code here because not all filesystems call
dio_complete() to do proper invalidation after O_DIRECT write.
Noticeable example is a blkdev_direct_IO().

This patch calls dio_warn_stale_pagecache() if invalidation fails.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
---
 mm/filemap.c |    8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index 189b8f318da2..dc3b78db079b 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -3241,11 +3241,13 @@ generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from)
 	 * do not end up with dio_complete() being called, so let's not break
 	 * them by removing it completely.
 	 *
+	 * Noticeable example is a blkdev_direct_IO().
+	 *
 	 * Skip invalidation for async writes or if mapping has no pages.
 	 */
-	if (written > 0 && mapping->nrpages)
-		invalidate_inode_pages2_range(mapping,
-					pos >> PAGE_SHIFT, end);
+	if (written > 0 && mapping->nrpages &&
+	    invalidate_inode_pages2_range(mapping, pos >> PAGE_SHIFT, end))
+		dio_warn_stale_pagecache(file);
 
 	if (written > 0) {
 		pos += written;