On mercoledì 20 aprile 2022 08:03:05 CEST Julia Lawall wrote:
>
> On Wed, 20 Apr 2022, Alaa Mohamed wrote:
>
> > kmap() is being deprecated and these usages are all local to the thread
> > so there is no reason kmap_local_page() can't be used.
> >
> > Replace kmap() calls with kmap_local_page().
>
> OK, so from a Coccinelle point of view, could we do
>
> @@
> expression e1,e2,x,f;
> @@
>
> e1 =
> - kmap
> + kmap_local_page
> (e2)
> ... when != x = e1 // not stored in any location and not passed to
another function
> when != f(...,e1,...)
> when != x = e2
> when != f(...,e2,...)
> -kunmap(e2)
> +kunmap_local(e1)
>
> julia
>
I've never spent sufficient time to understand properly the syntax and
semantics of expressions of Coccinelle. However, thanks Julia, this code
looks good and can be very helpful.
Only a minor objection... it doesn't tell when 'e2' has been allocated
within the same function where the kmap() call is.
In the particular case that I cite above, I'd prefer to remove the
allocation of the page (say with alloc_page()) and convert kmap() /kunmap()
to use kmalloc() / kfree().
Fox example, this is done in the following patch:
commit 633b0616cfe0 ("x86/sgx: Remove unnecessary kmap() from
sgx_ioc_enclave_init()") from Ira Weiny.
Can Coccinelle catch also those special cases where a page that is passed
to kmap() is allocated within that same function (vs. being passed as
argument to this function) and, if so, propose a replacement with
kmalloc()?
Thanks,
Fabio
On Wed, 20 Apr 2022, Fabio M. De Francesco wrote:
> On mercoledì 20 aprile 2022 08:03:05 CEST Julia Lawall wrote:
> >
> > On Wed, 20 Apr 2022, Alaa Mohamed wrote:
> >
> > > kmap() is being deprecated and these usages are all local to the thread
> > > so there is no reason kmap_local_page() can't be used.
> > >
> > > Replace kmap() calls with kmap_local_page().
> >
> > OK, so from a Coccinelle point of view, could we do
> >
> > @@
> > expression e1,e2,x,f;
> > @@
> >
> > e1 =
> > - kmap
> > + kmap_local_page
> > (e2)
> > ... when != x = e1 // not stored in any location and not passed to
> another function
> > when != f(...,e1,...)
> > when != x = e2
> > when != f(...,e2,...)
> > -kunmap(e2)
> > +kunmap_local(e1)
> >
> > julia
> >
>
> I've never spent sufficient time to understand properly the syntax and
> semantics of expressions of Coccinelle. However, thanks Julia, this code
> looks good and can be very helpful.
>
> Only a minor objection... it doesn't tell when 'e2' has been allocated
> within the same function where the kmap() call is.
OK, thanks for pointing that out. That seems like a key point that should
be mentioned in log messages. It's not even visible in the context lines
around the patch.
>
> In the particular case that I cite above, I'd prefer to remove the
> allocation of the page (say with alloc_page()) and convert kmap() /kunmap()
> to use kmalloc() / kfree().
>
> Fox example, this is done in the following patch:
>
> commit 633b0616cfe0 ("x86/sgx: Remove unnecessary kmap() from
> sgx_ioc_enclave_init()") from Ira Weiny.
>
> Can Coccinelle catch also those special cases where a page that is passed
> to kmap() is allocated within that same function (vs. being passed as
> argument to this function) and, if so, propose a replacement with
> kmalloc()?
Sure. I'll take a look at the precise example Alaa started with and see
if I can come up with something.
thanks,
julia
On Wed, 20 Apr 2022, Fabio M. De Francesco wrote:
> On mercoledì 20 aprile 2022 08:03:05 CEST Julia Lawall wrote:
> >
> > On Wed, 20 Apr 2022, Alaa Mohamed wrote:
> >
> > > kmap() is being deprecated and these usages are all local to the thread
> > > so there is no reason kmap_local_page() can't be used.
> > >
> > > Replace kmap() calls with kmap_local_page().
> >
> > OK, so from a Coccinelle point of view, could we do
> >
> > @@
> > expression e1,e2,x,f;
> > @@
> >
> > e1 =
> > - kmap
> > + kmap_local_page
> > (e2)
> > ... when != x = e1 // not stored in any location and not passed to
> another function
> > when != f(...,e1,...)
> > when != x = e2
> > when != f(...,e2,...)
> > -kunmap(e2)
> > +kunmap_local(e1)
> >
> > julia
> >
>
> I've never spent sufficient time to understand properly the syntax and
> semantics of expressions of Coccinelle. However, thanks Julia, this code
> looks good and can be very helpful.
>
> Only a minor objection... it doesn't tell when 'e2' has been allocated
> within the same function where the kmap() call is.
>
> In the particular case that I cite above, I'd prefer to remove the
> allocation of the page (say with alloc_page()) and convert kmap() /kunmap()
> to use kmalloc() / kfree().
>
> Fox example, this is done in the following patch:
>
> commit 633b0616cfe0 ("x86/sgx: Remove unnecessary kmap() from
> sgx_ioc_enclave_init()") from Ira Weiny.
>
> Can Coccinelle catch also those special cases where a page that is passed
> to kmap() is allocated within that same function (vs. being passed as
> argument to this function) and, if so, propose a replacement with
> kmalloc()?
It looks complex in this case, because the allocation is in another
function, and it is passed to another function.
julia
>
> Thanks,
>
> Fabio
>
>
>
>