Re: [External] Re: [PATCH v2] ext4: make dioread_nolock consistent in each mapping round

[hanjinke]

在 2023/2/16 下午9:13, Ritesh Harjani (IBM) 写道:
> Jinke Han <hanjinke.666@xxxxxxxxxxxxx> writes:
>
> > From: Jinke Han <hanjinke.666@xxxxxxxxxxxxx>
> >
> > When disable and enable dioread_nolock by remount, we may see
> > dioread_lock in ext4_do_writepages while see dioread_nolock in
> > mpage_map_one_extent. This inconsistency may triger the warning
> > in ext4_add_complete_io when the io_end->handle is NULL. Although
> > this warning is harmless in most cases, there is still a risk of
> > insufficient log reservation in conversion of unwritten extents.
>
> Sorry, I haven't completely gone through the patch yet. But this idea of
> caching the initial value of mount parameter and passing it do different
> functions while an I/O request completes, is not looking right to me.
>
> If that's the case shouldn't we disallow this mount option to change
> until all the outstanding I/O's are done or complete?
> Then we need not cache the value of dioread_nolock at the start of
> writepages and continue to pass it down in case it it changes.
>
> Just my initial thoughts.
>
> -ritesh

Fair enough, thanks.