Re: [PATCH 1/1] mm/page_poison: slightly optimize check_poison_mem()

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On 21.08.24 09:53, Zhen Lei wrote:
When the debug information needs to be suppressed due to ratelimit,
it is unnecessary to determine the end of the corrupted memory.

Signed-off-by: Zhen Lei <thunder.leizhen@xxxxxxxxxx>
---
  mm/page_poison.c | 7 ++++---
  1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/mm/page_poison.c b/mm/page_poison.c
index 3e9037363cf9d85..23fa799214720f1 100644
--- a/mm/page_poison.c
+++ b/mm/page_poison.c
@@ -55,14 +55,15 @@ static void check_poison_mem(struct page *page, unsigned char *mem, size_t bytes
  	if (!start)
  		return;
+ if (!__ratelimit(&ratelimit))
+		return;
+
  	for (end = mem + bytes - 1; end > start; end--) {
  		if (*end != PAGE_POISON)
  			break;
  	}
- if (!__ratelimit(&ratelimit))
-		return;
-	else if (start == end && single_bit_flip(*start, PAGE_POISON))
+	if (start == end && single_bit_flip(*start, PAGE_POISON))
  		pr_err("pagealloc: single bit error\n");
  	else
  		pr_err("pagealloc: memory corruption\n");

This way, you will be ratelimiting on every function call, possibly skipping PAGE_POISON checks even if there was no prior corruption detected?

--
Cheers,

David / dhildenb





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