The patch titled
Subject: mm/memory: use kmap_local_page() in __wp_page_copy_user()
has been added to the -mm mm-unstable branch. Its filename is
mm-memory-use-kmap_local_page-in-__wp_page_copy_user.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-memory-use-kmap_local_page-in-__wp_page_copy_user.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: "Fabio M. De Francesco" <fabio.maria.de.francesco@xxxxxxxxxxxxxxx>
Subject: mm/memory: use kmap_local_page() in __wp_page_copy_user()
Date: Mon, 20 Nov 2023 15:24:05 +0100
kmap_atomic() has been deprecated in favor of kmap_local_{folio,page}.
Therefore, replace kmap_atomic() with kmap_local_page in
__wp_page_copy_user().
kmap_atomic() disables preemption in !PREEMPT_RT kernels and
unconditionally disables also page-faults. My limited knowledge of the
implementation of __wp_page_copy_user() makes me think that the latter
side effect is still needed here, but kmap_local_page() is implemented not
to disable page-faults.
So, in addition to the conversion to local mapping, add explicit
pagefault_disable() / pagefault_enable() between mapping and un-mapping.
Link: https://lkml.kernel.org/r/20231120142418.6977-1-fmdefrancesco@xxxxxxxxx
Signed-off-by: Fabio M. De Francesco <fabio.maria.de.francesco@xxxxxxxxxxxxxxx>
Cc: Ira Weiny <ira.weiny@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memory.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
--- a/mm/memory.c~mm-memory-use-kmap_local_page-in-__wp_page_copy_user
+++ a/mm/memory.c
@@ -2841,7 +2841,8 @@ static inline int __wp_page_copy_user(st
* just copying from the original user address. If that
* fails, we just zero-fill it. Live with it.
*/
- kaddr = kmap_atomic(dst);
+ kaddr = kmap_local_page(dst);
+ pagefault_disable();
uaddr = (void __user *)(addr & PAGE_MASK);
/*
@@ -2909,7 +2910,8 @@ warn:
pte_unlock:
if (vmf->pte)
pte_unmap_unlock(vmf->pte, vmf->ptl);
- kunmap_atomic(kaddr);
+ pagefault_enable();
+ kunmap_local(kaddr);
flush_dcache_page(dst);
return ret;
_
Patches currently in -mm which might be from fabio.maria.de.francesco@xxxxxxxxxxxxxxx are
mm-memory-use-kmap_local_page-in-__wp_page_copy_user.patch
mm-mempool-replace-kmap_atomic-with-kmap_local_page.patch
mm-page_poison-replace-kmap_atomic-with-kmap_local_page.patch
