2022-08-15 14:56:58

by Alexey Romanov

Subject: [PATCH v1] zsmalloc: zs_object_copy: replace email link to doc

Emails are not documentation.

Signed-off-by: Alexey Romanov <[email protected]>
---
mm/zsmalloc.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 99d93a48cbe0..17641bde5432 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -1559,8 +1559,8 @@ static void zs_object_copy(struct size_class *class, unsigned long dst,
* 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/[email protected]/
+ * kunmap_atomic(d_addr). For more details see
+ * Documentation/mm/highmem
*/
if (s_off >= PAGE_SIZE) {
kunmap_atomic(d_addr);
--
2.25.1

2022-09-01 01:29:43

by Sergey Senozhatsky

Subject: Re: [PATCH v1] zsmalloc: zs_object_copy: replace email link to doc

On (22/08/15 17:48), Alexey Romanov wrote:
> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> index 99d93a48cbe0..17641bde5432 100644
> --- a/mm/zsmalloc.c
> +++ b/mm/zsmalloc.c
> @@ -1559,8 +1559,8 @@ static void zs_object_copy(struct size_class *class, unsigned long dst,
> * 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/[email protected]/
> + * kunmap_atomic(d_addr). For more details see
> + * Documentation/mm/highmem
> */
> if (s_off >= PAGE_SIZE) {
> kunmap_atomic(d_addr);

So I'm not against this patch, but in general I don't think we document
kmap_atomic/kunmap_atomic in the kernel. That's type of API that people
get BUG() on and then figure out that it's a stack and pop-s should
mirror push-es. We have lots of undocumented src/dst kmap-s:

src = kmap_atomic(s_page);
dst = kmap_atomic(d_page);
do_copy_page(dst, src);
kunmap_atomic(dst);
kunmap_atomic(src);

Like I said, I'm not against this patch, so FWIW
Reviewed-by: Sergey Senozhatsky <[email protected]>

I'll let Minchan to have the final word.