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authorAndy Grover <andy.grover@oracle.com>2009-04-09 16:45:29 -0700
committerIngo Molnar <mingo@elte.hu>2009-04-10 13:14:08 +0200
commita0d22f485af1553060b4094ee0154537a8f6a8a6 (patch)
treeb0c3a9b325bb93e0777a422cc076eae5c150a6a4
parent746cddd37d48a166f170165a0df4bd50fde1ea60 (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>
-rw-r--r--arch/x86/mm/gup.c16
1 files changed, 16 insertions, 0 deletions
diff --git a/arch/x86/mm/gup.c b/arch/x86/mm/gup.c
index be54176e9eb..6340cef6798 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)
{