There is no point in doing an fdatasync to write out pages when switching away from direct I/O, as there won't be any. The writeback is only needed when switching to direct I/O, which would have to invalidate the pagecache less efficiently from the I/O path. Signed-off-by: Christoph Hellwig <hch@xxxxxx> --- drivers/block/loop.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/block/loop.c b/drivers/block/loop.c index 55bea9c95b45..cf80cdf5e440 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -203,8 +203,9 @@ static void __loop_update_dio(struct loop_device *lo, bool dio) if (lo->use_dio == use_dio) return; - /* flush dirty pages before changing direct IO */ - vfs_fsync(lo->lo_backing_file, 0); + /* flush dirty pages before starting to use direct I/O */ + if (use_dio) + vfs_fsync(lo->lo_backing_file, 0); /* * The flag of LO_FLAGS_DIRECT_IO is handled similarly with -- 2.45.2
