Re: [PATCH v2 1/2] mm/page_alloc: drop the unnecessary pfn_valid() for start pfn

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 





On 4/24/2023 6:54 PM, Michal Hocko wrote:
On Mon 24-04-23 18:46:40, Baolin Wang wrote:


On 4/24/2023 5:50 PM, Michal Hocko wrote:
On Sun 23-04-23 18:59:10, Baolin Wang wrote:
We've already used pfn_to_online_page() for start pfn to make sure

Who is we? I do not see any note explicitly requiring that start_pfn has
to be valid for __pageblock_pfn_to_page.

Sorry for confusing, what I mean is the __pageblock_pfn_to_page() function,
which has used pfn_to_online_page() for start pfn. So the pfn_valid() in
__pageblock_pfn_to_page() for start pfn is unnecessary.

I will update the commit log to make it clear.

Your comment suggested that the check _has_ already been done. Which is
not the case. pfn_to_online_page is called later in the function so I
guess you should rephrase as following:

"
__pageblock_pfn_to_page currently performs both pfn_valid check and
pfn_to_online_page. The former one is redundant because the latter is a
stronger check. Drop pfn_valid.
"

Yes, will change the commit log.


With that or something going along with that. Feel free to add
Acked-by: Michal Hocko <mhocko@xxxxxxxx>

Thanks.

it is online and valid, so the pfn_valid() for the start pfn is
unnecessary, drop it.

Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
Reviewed-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
---
Changes from v1:
   - Collect reviewed tags. Thanks David and Ying.
---
   mm/page_alloc.c | 2 +-
   1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 9de2a18519a1..6457b64fe562 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1512,7 +1512,7 @@ struct page *__pageblock_pfn_to_page(unsigned long start_pfn,
   	/* end_pfn is one past the range we are checking */
   	end_pfn--;
-	if (!pfn_valid(start_pfn) || !pfn_valid(end_pfn))
+	if (!pfn_valid(end_pfn))
   		return NULL;
   	start_page = pfn_to_online_page(start_pfn);
--
2.27.0






[Index of Archives]     [Linux ARM Kernel]     [Linux ARM]     [Linux Omap]     [Fedora ARM]     [IETF Annouce]     [Bugtraq]     [Linux OMAP]     [Linux MIPS]     [eCos]     [Asterisk Internet PBX]     [Linux API]

  Powered by Linux