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SubjectRe: [PATCH 5/6] mlock: do not hold mmap_sem for extended periods of time
On Thu,  2 Dec 2010 16:16:51 -0800
Michel Lespinasse <walken@google.com> wrote:

> __get_user_pages gets a new 'nonblocking' parameter to signal that the
> caller is prepared to re-acquire mmap_sem and retry the operation if needed.
> This is used to split off long operations if they are going to block on
> a disk transfer, or when we detect contention on the mmap_sem.

Doesn't apply to linux-next because the KVM guys snuck in a new
FAULT_FLAG_MINOR (who knew?). With a bonus, undocumented,
exported-to-modules get_user_pages_noio().

I liked your code better so I munged __get_user_pages() together thusly:


cond_resched();
while (!(page = follow_page(vma, start, foll_flags))) {
int ret;
unsigned int fault_flags = 0;
if (foll_flags & FOLL_WRITE)
fault_flags |= FAULT_FLAG_WRITE;
if (nonblocking)
fault_flags |= FAULT_FLAG_ALLOW_RETRY;
if (foll_flags & FOLL_MINOR)
fault_flags |= FAULT_FLAG_MINOR;
ret = handle_mm_fault(mm, vma, start,
fault_flags);


please review the end result..


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