diff options
author | Huang Ying <ying.huang@intel.com> | 2011-01-30 03:15:47 (GMT) |
---|---|---|
committer | Marcelo Tosatti <mtosatti@redhat.com> | 2011-03-17 16:08:27 (GMT) |
commit | 0014bd990e69063b0fb78940b35439d7980ce3ee (patch) | |
tree | 56d4576cc07954eb304abaf602aba44a6aa2a4f1 /mm/memory.c | |
parent | 91c9c3eda4f3066980d13a6907ef84f3a99364bd (diff) | |
download | linux-0014bd990e69063b0fb78940b35439d7980ce3ee.tar.xz |
mm: export __get_user_pages
In most cases, get_user_pages and get_user_pages_fast should be used
to pin user pages in memory. But sometimes, some special flags except
FOLL_GET, FOLL_WRITE and FOLL_FORCE are needed, for example in
following patch, KVM needs FOLL_HWPOISON. To support these users,
__get_user_pages is exported directly.
There are some symbol name conflicts in infiniband driver, fixed them too.
Signed-off-by: Huang Ying <ying.huang@intel.com>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: Michel Lespinasse <walken@google.com>
CC: Roland Dreier <roland@kernel.org>
CC: Ralph Campbell <infinipath@qlogic.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Diffstat (limited to 'mm/memory.c')
-rw-r--r-- | mm/memory.c | 50 |
1 files changed, 50 insertions, 0 deletions
diff --git a/mm/memory.c b/mm/memory.c index 5823698..806a37e 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1410,6 +1410,55 @@ no_page_table: return page; } +/** + * __get_user_pages() - pin user pages in memory + * @tsk: task_struct of target task + * @mm: mm_struct of target mm + * @start: starting user address + * @nr_pages: number of pages from start to pin + * @gup_flags: flags modifying pin behaviour + * @pages: array that receives pointers to the pages pinned. + * Should be at least nr_pages long. Or NULL, if caller + * only intends to ensure the pages are faulted in. + * @vmas: array of pointers to vmas corresponding to each page. + * Or NULL if the caller does not require them. + * @nonblocking: whether waiting for disk IO or mmap_sem contention + * + * 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. Each page returned must be released + * with a put_page() call when it is finished with. vmas will only + * remain valid while mmap_sem is held. + * + * Must be called with mmap_sem held for read or write. + * + * __get_user_pages walks a process's page tables and takes a reference to + * each struct page that each user address corresponds to at a given + * instant. That is, it takes the page that would be accessed if a user + * thread accesses the given user virtual address at that instant. + * + * This does not guarantee that the page exists in the user mappings when + * __get_user_pages returns, and there may even be a completely different + * page there in some cases (eg. if mmapped pagecache has been invalidated + * and subsequently re faulted). However it does guarantee that the page + * won't be freed completely. And mostly callers simply care that the page + * contains data that was valid *at some point in time*. Typically, an IO + * or similar operation cannot guarantee anything stronger anyway because + * locks can't be held over the syscall boundary. + * + * If @gup_flags & FOLL_WRITE == 0, the page must not be written to. If + * the page is written to, set_page_dirty (or set_page_dirty_lock, as + * appropriate) must be called after the page is finished with, and + * before put_page is called. + * + * If @nonblocking != NULL, __get_user_pages will not wait for disk IO + * or mmap_sem contention, and if waiting is needed to pin all pages, + * *@nonblocking will be set to 0. + * + * In most cases, get_user_pages or get_user_pages_fast should be used + * instead of __get_user_pages. __get_user_pages should be used only if + * you need some special @gup_flags. + */ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm, unsigned long start, int nr_pages, unsigned int gup_flags, struct page **pages, struct vm_area_struct **vmas, @@ -1578,6 +1627,7 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm, } while (nr_pages); return i; } +EXPORT_SYMBOL(__get_user_pages); /** * get_user_pages() - pin user pages in memory |