On Tue, May 20, 2025 at 02:46:22PM +0200, Christian Hesse wrote: > "Xu, Lizhi" <Lizhi.Xu@xxxxxxxxxxxxx> on Tue, 2025/05/20 12:27: > > If it is a regular file, generic_ro_fops is used. In this case, > > isofs supports read_iter. When a regular file has a writable attribute, > > Just tested with an iso file where writable flag from loopback file inside > was explicitly removed. No change. > > > the problem will recur because isofs does not support write_iter. > > We have two indications here that setup should happen in read-only mode: > > * The underlaying filesystem is read-only > * `losetup` is called with switch `--read-only` > > I would expect both to make this happy. Can you test this patch? We historically allow a writable fd on block devices even when they are read-only. I suspect your use case is doing that and the new check for write_iter is interfering with that: diff --git a/drivers/block/loop.c b/drivers/block/loop.c index b8ba7de08753..e2b1f377f585 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -979,9 +979,6 @@ static int loop_configure(struct loop_device *lo, blk_mode_t mode, if (!file) return -EBADF; - if ((mode & BLK_OPEN_WRITE) && !file->f_op->write_iter) - return -EINVAL; - error = loop_check_backing_file(file); if (error) return error;
