On Tue, May 17, 2022 at 10:20:06PM +0000, Al Viro wrote:
> On Thu, May 12, 2022 at 08:29:10AM +1000, Daniil Lunev wrote:
> > Force unmount of FUSE severes the connection with the user space, even
> > if there are still open files. Subsequent remount tries to re-use the
> > superblock held by the open files, which is meaningless in the FUSE case
> > after disconnect - reused super block doesn't have userspace counterpart
> > attached to it and is incapable of doing any IO.
>
> Why not simply have those simply rejected by fuse_test_super()?
> Looks like that would be much smaller and less invasive patch...
> Confused...
... because Miklos had suggested that, apparently ;-/ I disagree -
that approach has more side effects. "mount will skip that sucker" is,
AFAICS, the only effect of modiyfing test_super callback(s); yours, OTOH...
Note that generic_shutdown_super() is *not* called while superblock is
mounted anywhere. And it doesn't get to eviction from the list while it still
has live dentries. Or inodes, for that matter.
So this
if (sb->s_bdi != &noop_backing_dev_info) {
if (sb->s_iflags & SB_I_PERSB_BDI)
bdi_unregister(sb->s_bdi);
bdi_put(sb->s_bdi);
sb->s_bdi = &noop_backing_dev_info;
}
is almost certainly not safe to be done on a live superblock.
