Re: [PATCH v3] intel: igb: igb_ethtool.c: Convert kmap() to kmap_local_page()

["Fabio M. De Francesco" <fmdefrancesco@gmail.com>]

On sabato 16 aprile 2022 17:52:20 CEST Fabio M. De Francesco wrote:
> If all calls should be changed with no regards to the surrounding 
contexts 
> and special situations, we can just make an automated s/kmap()/
> kmap_local_page()/ or something else similar

(I'm afraid that somehow I messed up with the HTML filters in KMail 
therefore I have to send this email again to the Outreachy list because 
this message has already been rejected twice - I hope this time it works). 

Hi Julia, 
  
Of course I was just kidding when talking of massively automated 

substitutions. They are not feasible and we cannot blindly replace all 
kmap() calls with kmap_local_page(). 

Although these code changes look good, your objections are appropriate and 
legitimate. 

Not all kmap() calls can be changed to kmap_local_page() and, if someone 
wants to make such replacements, they should also "prove" somehow that they 
are doing the right changes in that specific context. 

For example, the following is one of those cases where such a replacement 
is not allowed and a different solution has yet to be found: 

https://lore.kernel.org/lkml/2a7030f5-d55f-94c7-90ba-5a57235159f6@amd.com/ 

Furthermore, if people cannot "prove" that this change is feasible, their 
patches will probably be ignored / rejected just because many maintainers 
still don't know if those changes are correct and safe. 

Whoever wants to do these changes should understand the specific context in 
which they are working. 

For example, there have also been cases where alloc_page() + kmap() was 
simply replaced by kmalloc(). Sure! 

If you are interested to see how and why, please take a look at the commit 
633b0616cfe0 ("x86/sgx: Remove unnecessary kmap() from 
sgx_ioc_enclave_init()") from Ira Weiny. 

Regards, 

Fabio