Re: [RFC PATCH] mm/highmem: VM_BUG_ON() if offset + len > PAGE_SIZE

[Fabio M. De Francesco]

On lunedì 25 aprile 2022 18:47:18 CEST Ira Weiny wrote:
> On Mon, Apr 25, 2022 at 03:47:38AM +0200, Fabio M. De Francesco wrote:
> > On domenica 24 aprile 2022 12:48:06 CEST Fabio M. De Francesco wrote:
> > > Call VM_BUG_ON() if offset + len > PAGE_SIZE.
> > > 
> > > This is an RFC patch because I'm not sure if we actually need to 
> > BUG_ON(),
> > 
> > Actually I considered VM_BUG_ON() for consistency with the other 
functions 
> > in highmem.h
> > 
> > What about VM_WARN_ON_ONCE() here and also in memset_page?
> 
> For consistency leave this as a VM_BUG_ON[1]
> 
> I've been down a similar path[2] and there was a long discussion about 
it.[3]
> 
> In the end we settled on VM_BUG_ON.[4]

Thanks for your reply and for providing so many helpful links :)

I just read the ones related to VM_BUG_ON() (I don't have time for 
flush_dcache_page() today). Since the consensus for these kinds of issues 
is in favor of using VM_BUG_ON(), that's OK for me.

I will send a "real" patch by tomorrow.

Again, thanks,

Fabio

> As to the addition of flush_dcache_page().  There was a discussion here.
> 
> https://lore.kernel.org/lkml/CAHk-=wiKac4t-fOP_3fAf7nETfFLhT3ShmRmBq2J96y6jAr56Q@xxxxxxxxxxxxxx/
> 
> Ira
> 
> [1] https://lore.kernel.org/lkml/20210209205249.GB2975576@xxxxxxxxxxxxxxxxxxxxxxxxx/
> 
> [2] https://lore.kernel.org/lkml/20201209022250.GP1563847@xxxxxxxxxxxxxxxxxxxxxxxxx/
> 
> [3] https://lore.kernel.org/lkml/20201208213255.GO1563847@xxxxxxxxxxxxxxxxxxxxxxxxx/
> 
> [4] https://lore.kernel.org/lkml/20210210174928.3156073-1-ira.weiny@xxxxxxxxx/