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| author | Nick Piggin <nickpiggin@yahoo.com.au> | 2009-06-16 15:31:39 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-06-16 19:47:30 -0700 |
| commit | d2bf6be8ab63aa84e6149aac934649aadf3828b1 (patch) | |
| tree | 65e7f74f1ed6fd9516f1615b0f293d2aaeede07b /mm/util.c | |
| parent | 7ffc59b4d0bdfa00e882339f85b8a969bb7021e2 (diff) | |
| download | lwn-d2bf6be8ab63aa84e6149aac934649aadf3828b1.tar.gz lwn-d2bf6be8ab63aa84e6149aac934649aadf3828b1.zip | |
mm: clean up get_user_pages_fast() documentation
Move more documentation for get_user_pages_fast into the new kerneldoc comment.
Add some comments for get_user_pages as well.
Also, move get_user_pages_fast declaration up to get_user_pages. It wasn't
there initially because it was once a static inline function.
[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Andy Grover <andy.grover@oracle.com>
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, 12 insertions, 4 deletions
diff --git a/mm/util.c b/mm/util.c index abc65aa7cdfc..d5d2213728c5 100644 --- a/mm/util.c +++ b/mm/util.c @@ -233,13 +233,21 @@ void arch_pick_mmap_layout(struct mm_struct *mm) * @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. + * + * get_user_pages_fast provides equivalent functionality to get_user_pages, + * operating on current and current->mm, with force=0 and vma=NULL. However + * unlike get_user_pages, it must be called without mmap_sem held. + * + * get_user_pages_fast may take mmap_sem and page table locks, so no + * assumptions can be made about lack of locking. get_user_pages_fast is to be + * implemented in a way that is advantageous (vs get_user_pages()) when the + * user memory area is already faulted in and present in ptes. However if the + * pages have to be faulted in, it may turn out to be slightly slower so + * callers need to carefully consider what to use. On many architectures, + * get_user_pages_fast simply falls back to get_user_pages. */ int __attribute__((weak)) get_user_pages_fast(unsigned long start, int nr_pages, int write, struct page **pages) |