On 22.02.24 17:24, Matthew Cassell wrote:
Resending due to plain-text email issue that caused mailing list to get skipped. Thank you for the feedback. I agree with you and would prefer to use bytes/kbytes. Here are the 2 concerns that led to me keeping it as pages: 1. Reduce the impact of the patch. Here is the call trace to reach the failure warning: <… usual mmap() stuff …> mmap_region() -> security_enough_memory_mm() -> __vm_enough_memory() Within mmap_region(), the length variable originally passed to mmap() gets right-shifted to get the page count. My first thought was to add an additional an additional argument to security_enough_memory_mm() of type unsigned long to keep that variable, but saw a handful of calls to it that would have to conform to the change. Not that I do not think this debug statement does not warrant that, I felt the less impact, the better. 2. Concerned about losing bits. When converting back to bytes I was worried about the loss of precision and printing that number back to users: unsigned long bytes_failed = pages << (PAGE_SHIFT);
In which scenario would you imagine that we lose precision? In other words, how would someone be able to create a VMA that is larger than what we can fit into an unsigned long in bytes?
I'd simply print "pages << PAGE_SHIFT" here and not worry about that :) -- Cheers, David / dhildenb
