Messages in this thread | | | From | KOSAKI Motohiro <> | Subject | Re: [PATCH 1/1] Document get_user_pages_fast() | Date | Fri, 10 Apr 2009 11:17:22 +0900 (JST) |
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> +/** > + * get_user_pages_fast() - pin user pages in memory > + * @start: starting user address > + * @nr_pages: number of pages from start to pin > + * @write: whether pages will be written to > + * @pages: array that receives pointers to the pages pinned. > + * Should be at least nr_pages long. > + * > + * Attempt to pin user pages in memory without taking mm->mmap_sem. > + * If not successful, it will fall back to taking the lock and > + * calling get_user_pages(). > + * > + * Returns number of pages pinned. This may be fewer than the number > + * requested. If nr_pages is 0 or negative, returns 0. If no pages > + * were pinned, returns -errno. > + */ > int __attribute__((weak)) get_user_pages_fast(unsigned long start, > int nr_pages, int write, struct page **pages) > {
There is one problem. gup and get_page() don't provide any page pinning.
get_page() only gurantee not freed. but don't gurantee to prevent page reclaim and Cow change owner process.
Yes, current all gup caller have serious bug. especially direct-io, aio, bio are broken.
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