Re: [PATCH] mm/vmalloc: Check absolute error return from vmap_[p4d|pud|pmd|pte]_range()

[Anshuman Khandual]

On 06/13/2019 09:01 PM, Matthew Wilcox wrote:
> On Thu, Jun 13, 2019 at 08:51:17PM +0530, Anshuman Khandual wrote:
>> acceptable ? What we have currently is wrong where vmap_pmd_range() could
>> just wrap EBUSY as ENOMEM and send up the call chain.
> 
> It's not wrong.  We do it in lots of places.  Unless there's a caller
> which really needs to know the difference, it's often better than
> returning the "real error".

I can understand the fact that because there are no active users of this
return code, the current situation has been alright. But then I fail to
understand how can EBUSY be made ENOMEM and let the caller to think that
vmap_page_rage() failed because of lack of memory when it is clearly not
the case. It is really surprising how it can be acceptable inside kernel
(init_mm) page table functions which need to be thorough enough.