The patch titled
Subject: mm/zswap: replace kmap_atomic() with kmap_local_page()
has been added to the -mm mm-unstable branch. Its filename is
mm-zswap-replace-kmap_atomic-with-kmap_local_page.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-zswap-replace-kmap_atomic-with-kmap_local_page.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: "Fabio M. De Francesco" <fabio.maria.de.francesco@xxxxxxxxxxxxxxx>
Subject: mm/zswap: replace kmap_atomic() with kmap_local_page()
Date: Mon, 27 Nov 2023 16:55:21 +0100
kmap_atomic() has been deprecated in favor of kmap_local_page().
Therefore, replace kmap_atomic() with kmap_local_page() in
zswap.c.
kmap_atomic() is implemented like a kmap_local_page() which also disables
page-faults and preemption (the latter only in !PREEMPT_RT kernels). The
kernel virtual addresses returned by these two API are only valid in the
context of the callers (i.e., they cannot be handed to other threads).
With kmap_local_page() the mappings are per thread and CPU local like in
kmap_atomic(); however, they can handle page-faults and can be called from
any context (including interrupts). The tasks that call kmap_local_page()
can be preempted and, when they are scheduled to run again, the kernel
virtual addresses are restored and are still valid.
In mm/zswap.c, the blocks of code between the mappings and un-mappings do
not depend on the above-mentioned side effects of kmap_atomic(), so that
the mere replacements of the old API with the new one is all that is
required (i.e., there is no need to explicitly call pagefault_disable()
and/or preempt_disable()).
Link: https://lkml.kernel.org/r/20231127160058.586446-1-fabio.maria.de.francesco@xxxxxxxxxxxxxxx
Signed-off-by: Fabio M. De Francesco <fabio.maria.de.francesco@xxxxxxxxxxxxxxx>
Cc: Ira Weiny <ira.weiny@xxxxxxxxx>
Cc: Seth Jennings <sjenning@xxxxxxxxxx>
Cc: Dan Streetman <ddstreet@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/zswap.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
--- a/mm/zswap.c~mm-zswap-replace-kmap_atomic-with-kmap_local_page
+++ a/mm/zswap.c
@@ -1267,16 +1267,16 @@ bool zswap_store(struct folio *folio)
}
if (zswap_same_filled_pages_enabled) {
- src = kmap_atomic(page);
+ src = kmap_local_page(page);
if (zswap_is_page_same_filled(src, &value)) {
- kunmap_atomic(src);
+ kunmap_local(src);
entry->swpentry = swp_entry(type, offset);
entry->length = 0;
entry->value = value;
atomic_inc(&zswap_same_filled_pages);
goto insert_entry;
}
- kunmap_atomic(src);
+ kunmap_local(src);
}
if (!zswap_non_same_filled_pages_enabled)
@@ -1422,9 +1422,9 @@ bool zswap_load(struct folio *folio)
spin_unlock(&tree->lock);
if (!entry->length) {
- dst = kmap_atomic(page);
+ dst = kmap_local_page(page);
zswap_fill_page(dst, entry->value);
- kunmap_atomic(dst);
+ kunmap_local(dst);
ret = true;
goto stats;
}
_
Patches currently in -mm which might be from fabio.maria.de.francesco@xxxxxxxxxxxxxxx are
mm-util-use-kmap_local_page-in-memcmp_pages.patch
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
mm-zswap-replace-kmap_atomic-with-kmap_local_page.patch
mm-swapfile-replace-kmap_atomic-with-kmap_local_page.patch
