From: Omar Sandoval <osandov@xxxxxx> The physical block size is "the lowest possible sector size that the hardware can operate on without reverting to read-modify-write operations" (from the comment on blk_queue_physical_block_size()). Since loop does buffered I/O on the backing file by default, the RMW unit is a page. This isn't the case for direct I/O mode, but let's keep it simple. Signed-off-by: Omar Sandoval <osandov@xxxxxx> --- drivers/block/loop.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/block/loop.c b/drivers/block/loop.c index 54e091887199..1a5b4ecf54ec 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -1764,6 +1764,8 @@ static int loop_add(struct loop_device **l, int i) } lo->lo_queue->queuedata = lo; + blk_queue_physical_block_size(lo->lo_queue, PAGE_SIZE); + /* * It doesn't make sense to enable merge because the I/O * submitted to backing file is handled page by page. -- 2.14.1
