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| author | Andy Grover <andy.grover@oracle.com> | 2009-04-13 23:40:05 +0200 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-04-14 00:04:32 +0200 |
| commit | 9de100d001564f58c3fb2ec1bd03e540ac0aa357 (patch) | |
| tree | ee7d599718821e0d272d3d63325ad940fc982e0e /mm/util.c | |
| parent | initramfs: fix initramfs to work with hardlinked init (diff) | |
| download | linux-9de100d001564f58c3fb2ec1bd03e540ac0aa357.tar.xz linux-9de100d001564f58c3fb2ec1bd03e540ac0aa357.zip | |
mm: document get_user_pages_fast()
While better than get_user_pages(), the usage of gupf(), especially the
return values and the fact that it can potentially only partially pin the
range, warranted some documentation.
Signed-off-by: Andy Grover <andy.grover@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/util.c')
| -rw-r--r-- | mm/util.c | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/mm/util.c b/mm/util.c index 2599e83eea17..55bef160b9f1 100644 --- a/mm/util.c +++ b/mm/util.c @@ -223,6 +223,22 @@ void arch_pick_mmap_layout(struct mm_struct *mm) } #endif +/** + * 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) { |