On 03/25/24 at 12:16pm, Heiko Carstens wrote: > On Mon, Mar 25, 2024 at 06:09:26PM +0800, Baoquan He wrote: > > On 03/25/24 at 10:39am, Heiko Carstens wrote: > > > On Sun, Mar 24, 2024 at 04:32:00PM -0700, Christoph Hellwig wrote: > > > > On Sat, Mar 23, 2024 at 03:15:44PM +0100, Uladzislau Rezki (Sony) wrote: > > ......snip > > > > I guess this is ok as an urgend bandaid to get s390 booting again, > > > > but calling find_vmap_area before the vmap area is initialized > > > > seems an actual issue in the s390 mm init code. > > > > > > > > Adding the s390 maintainers to see if they have and idea how this could > > > > get fixed in a better way. > > > > > > I'm going to push the patch below to the s390 git tree later. This is not a > > > piece of art, but I wanted to avoid to externalize vmalloc's vmap_initialized, > > > or come up with some s390 specific change_page_attr_alias_early() variant where > > > sooner or later nobody remembers what "early" means. > > > > > > So this seems to be "good enough". > ... > > > Add a slab_is_available() check to change_page_attr_alias() in order to > > > avoid early calls into vmalloc code. slab_is_available() is not exactly > > > what is needed, but there is currently no other way to tell if the vmalloc > > > code is initialized or not, and there is no reason to expose > > > e.g. vmap_initialized from vmalloc to achieve the same. > > > > If so, I would rather add a vmalloc_is_available() to achieve the same. > > The added code and the code comment definitely will confuse people and > > make people to dig why. > > So after having given this a bit more thought I think Uladzislau's patch is > probably the best way to address this. > > It seems to be better that the vmalloc code would just do the right thing, > regardless how early it is called, instead of adding yet another > subsystem_xyz_is_available() call. > > Alternatively this could be addressed in s390 code with some sort of > "early" calls, but as already stated, sooner or later nobody would remember > what "early" means, and even if that would be remembered: would that > restriction still be valid? I agree, it's better to let vmalloc code do the thing right whether it's early ot not with Uladzislau's patch.
