The patch titled
Subject: lib: replace kmap() with kmap_local_page()
has been added to the -mm mm-nonmm-unstable branch. Its filename is
lib-replace-kmap-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/lib-replace-kmap-with-kmap_local_page.patch
This patch will later appear in the mm-nonmm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Sumitra Sharma <sumitraartsy@xxxxxxxxx>
Subject: lib: replace kmap() with kmap_local_page()
Date: Sat, 10 Jun 2023 10:57:12 -0700
kmap() has been deprecated in favor of the kmap_local_page() due to high
cost, restricted mapping space, the overhead of a global lock for
synchronization, and making the process sleep in the absence of free
slots.
kmap_local_page() is faster than kmap() and offers thread-local and
CPU-local mappings, take pagefaults in a local kmap region and preserves
preemption by saving the mappings of outgoing tasks and restoring those of
the incoming one during a context switch.
The mappings are kept thread local in the functions â??dmirror_do_readâ??
and â??dmirror_do_writeâ?? in test_hmm.c
Therefore, replace kmap() with kmap_local_page() and use
mempcy_from/to_page() to avoid open coding kmap_local_page() + memcpy() +
kunmap_local().
Remove the unused variable â??tmpâ??.
Link: https://lkml.kernel.org/r/20230610175712.GA348514@xxxxxxxxxxx
Signed-off-by: Sumitra Sharma <sumitraartsy@xxxxxxxxx>
Suggested-by: Fabio M. De Francesco <fmdefrancesco@xxxxxxxxx>
Reviewed-by: Fabio M. De Francesco <fmdefrancesco@xxxxxxxxx>
Reviewed-by: Ira Weiny <ira.weiny@xxxxxxxxx>
Cc: Deepak R Varma <drv@xxxxxxxxx>
Cc: Jérôme Glisse <jglisse@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
lib/test_hmm.c | 10 ++--------
1 file changed, 2 insertions(+), 8 deletions(-)
--- a/lib/test_hmm.c~lib-replace-kmap-with-kmap_local_page
+++ a/lib/test_hmm.c
@@ -368,16 +368,13 @@ static int dmirror_do_read(struct dmirro
for (pfn = start >> PAGE_SHIFT; pfn < (end >> PAGE_SHIFT); pfn++) {
void *entry;
struct page *page;
- void *tmp;
entry = xa_load(&dmirror->pt, pfn);
page = xa_untag_pointer(entry);
if (!page)
return -ENOENT;
- tmp = kmap(page);
- memcpy(ptr, tmp, PAGE_SIZE);
- kunmap(page);
+ memcpy_from_page(ptr, page, 0, PAGE_SIZE);
ptr += PAGE_SIZE;
bounce->cpages++;
@@ -437,16 +434,13 @@ static int dmirror_do_write(struct dmirr
for (pfn = start >> PAGE_SHIFT; pfn < (end >> PAGE_SHIFT); pfn++) {
void *entry;
struct page *page;
- void *tmp;
entry = xa_load(&dmirror->pt, pfn);
page = xa_untag_pointer(entry);
if (!page || xa_pointer_tag(entry) != DPT_XA_TAG_WRITE)
return -ENOENT;
- tmp = kmap(page);
- memcpy(tmp, ptr, PAGE_SIZE);
- kunmap(page);
+ memcpy_to_page(page, 0, ptr, PAGE_SIZE);
ptr += PAGE_SIZE;
bounce->cpages++;
_
Patches currently in -mm which might be from sumitraartsy@xxxxxxxxx are
lib-replace-kmap-with-kmap_local_page.patch
