The patch titled
Subject: zsmalloc: zs_object_copy: add clarifying comment
has been added to the -mm mm-unstable branch. Its filename is
zsmalloc-zs_object_copy-add-clarifying-comment.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/zsmalloc-zs_object_copy-add-clarifying-comment.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: Alexey Romanov <avromanov@xxxxxxxxxxxxxx>
Subject: zsmalloc: zs_object_copy: add clarifying comment
Date: Thu, 11 Aug 2022 18:37:54 +0300
Patch series "tidy up zsmalloc implementation"
This patchset remove some unnecessary checks and adds a clarifying
comment. While analysing zs_object_copy() function code, I spent some
time to understand what the call kunmap_atomic(d_addr) is for. It seems
that this point is not trivial and it is worth adding a comment.
This patch (of 2):
It's not obvious why kunmap_atomic(d_addr) call is needed.
Link: https://lkml.kernel.org/r/20220811153755.16102-1-avromanov@xxxxxxxxxxxxxx
Link: https://lkml.kernel.org/r/20220811153755.16102-2-avromanov@xxxxxxxxxxxxxx
Signed-off-by: Alexey Romanov <avromanov@xxxxxxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
Cc: Nitin Gupta <ngupta@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/zsmalloc.c | 6 ++++++
1 file changed, 6 insertions(+)
--- a/mm/zsmalloc.c~zsmalloc-zs_object_copy-add-clarifying-comment
+++ a/mm/zsmalloc.c
@@ -1555,6 +1555,12 @@ static void zs_object_copy(struct size_c
d_off += size;
d_size -= size;
+ /* Calling kunmap_atomic(d_addr) is necessary. kunmap_atomic() calls
+ * must occurs in reverse order of calls to kmap_atomic().
+ * So, to call kunmap_atomic(s_addr) we should first call kunmap_atomic(d_addr).
+ * For more details see:
+ * https://lore.kernel.org/linux-mm/5512421D.4000603@xxxxxxxxxxx/
+ */
if (s_off >= PAGE_SIZE) {
kunmap_atomic(d_addr);
kunmap_atomic(s_addr);
_
Patches currently in -mm which might be from avromanov@xxxxxxxxxxxxxx are
zsmalloc-zs_object_copy-add-clarifying-comment.patch
zsmalloc-remove-unnecessary-size_class-null-check.patch
