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Date: Wed, 20 Apr 2022 15:22:10 +0200 From: "Fabio M. De Francesco" <fmdefrancesco@...il.com> To: Julia Lawall <julia.lawall@...ia.fr>, ira.weiny@...el.com Cc: Alaa Mohamed <eng.alaamohamedsoliman.am@...il.com>, outreachy@...ts.linux.dev, boris.ostrovsky@...cle.com, jgross@...e.com, sstabellini@...nel.org, xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH v2] xen: Convert kmap() to kmap_local_page() 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
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