diff options
| author | Alexey Romanov | 2022-08-11 18:37:54 +0300 |
|---|---|---|
| committer | Andrew Morton | 2022-09-11 20:25:49 -0700 |
| commit | 050a388b7f05b13dbcc5b6f14a4c7565a69a5020 (patch) | |
| tree | e2dd0fcfd8b8ee8a5904c3ef5e2a278a5c625ca8 | |
| parent | e9c2dbc8bf71a5039604a1dc45b10f24a2098f3b (diff) | |
zsmalloc: zs_object_copy: add clarifying comment
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.
[akpm@linux-foundation.org: tweak comment layout]
Link: https://lkml.kernel.org/r/20220811153755.16102-1-avromanov@sberdevices.ru
Link: https://lkml.kernel.org/r/20220811153755.16102-2-avromanov@sberdevices.ru
Signed-off-by: Alexey Romanov <avromanov@sberdevices.ru>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
| -rw-r--r-- | mm/zsmalloc.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c index 907c9b1e1e61..09ab91a3fa3f 100644 --- a/mm/zsmalloc.c +++ b/mm/zsmalloc.c @@ -1555,6 +1555,13 @@ static void zs_object_copy(struct size_class *class, unsigned long dst, 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@samsung.com/ + */ if (s_off >= PAGE_SIZE) { kunmap_atomic(d_addr); kunmap_atomic(s_addr); |