Re: 回复: [PATCH V5] loop: Add sanity check for read/write_iter

[hch@xxxxxxxxxxxxx]

On Tue, May 20, 2025 at 06:29:48AM +0000, Xu, Lizhi wrote:
> I figured out your steps to reproduce, and yes, this problem will occur if you do losetup with a file in a filesystem that does not support read_iter, which is what this patch does.

isofs does support read_iter, without that it would not have worked
before either. That is not the problem.  It must be related to
the FMODE_WRITE check - i.e. we have a writable FD here, but a file
system that does not actually supports writes.  Which honestly feels
weird, but we'll have to figure it out to unbreak these setups.