diff options
| author | Andy Grover <andy.grover@oracle.com> | 2009-04-09 16:45:29 -0700 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2009-04-10 13:14:08 +0200 |
| commit | a0d22f485af1553060b4094ee0154537a8f6a8a6 (patch) | |
| tree | b0c3a9b325bb93e0777a422cc076eae5c150a6a4 /arch/x86/mm/gup.c | |
| parent | 746cddd37d48a166f170165a0df4bd50fde1ea60 (diff) | |
x86: 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: npiggin@suse.de
Cc: akpm@linux-foundation.org
LKML-Reference: <1239320729-3262-1-git-send-email-andy.grover@oracle.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch/x86/mm/gup.c')
| -rw-r--r-- | arch/x86/mm/gup.c | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/arch/x86/mm/gup.c b/arch/x86/mm/gup.c index be54176e9eb2..6340cef6798a 100644 --- a/arch/x86/mm/gup.c +++ b/arch/x86/mm/gup.c @@ -219,6 +219,22 @@ static int gup_pud_range(pgd_t pgd, unsigned long addr, unsigned long end, return 1; } +/** + * 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 get_user_pages_fast(unsigned long start, int nr_pages, int write, struct page **pages) { |