[merged mm-nonmm-stable] lib-replace-kmap-with-kmap_local_page.patch removed from -mm tree

[merged mm-nonmm-stable] lib-replace-kmap-with-kmap_local_page.patch removed from -mm tree

[Andrew Morton]

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The quilt patch titled
     Subject: lib: replace kmap() with kmap_local_page()
has been removed from the -mm tree.  Its filename was
     lib-replace-kmap-with-kmap_local_page.patch

This patch was dropped because it was merged into the mm-nonmm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Sumitra Sharma <sumitraartsy@gmail.com>
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 “dmirror_do_read”
and “dmirror_do_write” 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 “tmp”.

Link: https://lkml.kernel.org/r/20230610175712.GA348514@sumitra.com
Signed-off-by: Sumitra Sharma <sumitraartsy@gmail.com>
Suggested-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Reviewed-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Cc: Deepak R Varma <drv@mailo.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 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@gmail.com are