From 932f4a630a695212bdc7379b05f9bd0dafc5d968 Mon Sep 17 00:00:00 2001 From: Ira Weiny Date: Mon, 13 May 2019 17:17:03 -0700 Subject: mm/gup: replace get_user_pages_longterm() with FOLL_LONGTERM Pach series "Add FOLL_LONGTERM to GUP fast and use it". HFI1, qib, and mthca, use get_user_pages_fast() due to its performance advantages. These pages can be held for a significant time. But get_user_pages_fast() does not protect against mapping FS DAX pages. Introduce FOLL_LONGTERM and use this flag in get_user_pages_fast() which retains the performance while also adding the FS DAX checks. XDP has also shown interest in using this functionality.[1] In addition we change get_user_pages() to use the new FOLL_LONGTERM flag and remove the specialized get_user_pages_longterm call. [1] https://lkml.org/lkml/2019/3/19/939 "longterm" is a relative thing and at this point is probably a misnomer. This is really flagging a pin which is going to be given to hardware and can't move. I've thought of a couple of alternative names but I think we have to settle on if we are going to use FL_LAYOUT or something else to solve the "longterm" problem. Then I think we can change the flag to a better name. Secondly, it depends on how often you are registering memory. I have spoken with some RDMA users who consider MR in the performance path... For the overall application performance. I don't have the numbers as the tests for HFI1 were done a long time ago. But there was a significant advantage. Some of which is probably due to the fact that you don't have to hold mmap_sem. Finally, architecturally I think it would be good for everyone to use *_fast. There are patches submitted to the RDMA list which would allow the use of *_fast (they reworking the use of mmap_sem) and as soon as they are accepted I'll submit a patch to convert the RDMA core as well. Also to this point others are looking to use *_fast. As an aside, Jasons pointed out in my previous submission that *_fast and *_unlocked look very much the same. I agree and I think further cleanup will be coming. But I'm focused on getting the final solution for DAX at the moment. This patch (of 7): This patch starts a series which aims to support FOLL_LONGTERM in get_user_pages_fast(). Some callers who would like to do a longterm (user controlled pin) of pages with the fast variant of GUP for performance purposes. Rather than have a separate get_user_pages_longterm() call, introduce FOLL_LONGTERM and change the longterm callers to use it. This patch does not change any functionality. In the short term "longterm" or user controlled pins are unsafe for Filesystems and FS DAX in particular has been blocked. However, callers of get_user_pages_fast() were not "protected". FOLL_LONGTERM can _only_ be supported with get_user_pages[_fast]() as it requires vmas to determine if DAX is in use. NOTE: In merging with the CMA changes we opt to change the get_user_pages() call in check_and_migrate_cma_pages() to a call of __get_user_pages_locked() on the newly migrated pages. This makes the code read better in that we are calling __get_user_pages_locked() on the pages before and after a potential migration. As a side affect some of the interfaces are cleaned up but this is not the primary purpose of the series. In review[1] it was asked: > This I don't get - if you do lock down long term mappings performance > of the actual get_user_pages call shouldn't matter to start with. > > What do I miss? A couple of points. First "longterm" is a relative thing and at this point is probably a misnomer. This is really flagging a pin which is going to be given to hardware and can't move. I've thought of a couple of alternative names but I think we have to settle on if we are going to use FL_LAYOUT or something else to solve the "longterm" problem. Then I think we can change the flag to a better name. Second, It depends on how often you are registering memory. I have spoken with some RDMA users who consider MR in the performance path... For the overall application performance. I don't have the numbers as the tests for HFI1 were done a long time ago. But there was a significant advantage. Some of which is probably due to the fact that you don't have to hold mmap_sem. Finally, architecturally I think it would be good for everyone to use *_fast. There are patches submitted to the RDMA list which would allow the use of *_fast (they reworking the use of mmap_sem) and as soon as they are accepted I'll submit a patch to convert the RDMA core as well. Also to this point others are looking to use *_fast. As an asside, Jasons pointed out in my previous submission that *_fast and *_unlocked look very much the same. I agree and I think further cleanup will be coming. But I'm focused on getting the final solution for DAX at the moment. [1] https://lore.kernel.org/lkml/20190220180255.GA12020@iweiny-DESK2.sc.intel.com/T/#md6abad2569f3bf6c1f03686c8097ab6563e94965 [ira.weiny@intel.com: v3] Link: http://lkml.kernel.org/r/20190328084422.29911-2-ira.weiny@intel.com Link: http://lkml.kernel.org/r/20190328084422.29911-2-ira.weiny@intel.com Link: http://lkml.kernel.org/r/20190317183438.2057-2-ira.weiny@intel.com Signed-off-by: Ira Weiny Reviewed-by: Andrew Morton Cc: Aneesh Kumar K.V Cc: Michal Hocko Cc: John Hubbard Cc: "Kirill A. Shutemov" Cc: Peter Zijlstra Cc: Jason Gunthorpe Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Cc: "David S. Miller" Cc: Martin Schwidefsky Cc: Heiko Carstens Cc: Rich Felker Cc: Yoshinori Sato Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Borislav Petkov Cc: Ralf Baechle Cc: James Hogan Cc: Dan Williams Cc: Mike Marshall Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- net/xdp/xdp_umem.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'net') diff --git a/net/xdp/xdp_umem.c b/net/xdp/xdp_umem.c index 989e52386c35..2b18223e7eb8 100644 --- a/net/xdp/xdp_umem.c +++ b/net/xdp/xdp_umem.c @@ -253,8 +253,8 @@ static int xdp_umem_pin_pages(struct xdp_umem *umem) return -ENOMEM; down_read(¤t->mm->mmap_sem); - npgs = get_user_pages_longterm(umem->address, umem->npgs, - gup_flags, &umem->pgs[0], NULL); + npgs = get_user_pages(umem->address, umem->npgs, + gup_flags | FOLL_LONGTERM, &umem->pgs[0], NULL); up_read(¤t->mm->mmap_sem); if (npgs != umem->npgs) { -- cgit From 73b0140bf0fe9df90fb267c00673c4b9bf285430 Mon Sep 17 00:00:00 2001 From: Ira Weiny Date: Mon, 13 May 2019 17:17:11 -0700 Subject: mm/gup: change GUP fast to use flags rather than a write 'bool' To facilitate additional options to get_user_pages_fast() change the singular write parameter to be gup_flags. This patch does not change any functionality. New functionality will follow in subsequent patches. Some of the get_user_pages_fast() call sites were unchanged because they already passed FOLL_WRITE or 0 for the write parameter. NOTE: It was suggested to change the ordering of the get_user_pages_fast() arguments to ensure that callers were converted. This breaks the current GUP call site convention of having the returned pages be the final parameter. So the suggestion was rejected. Link: http://lkml.kernel.org/r/20190328084422.29911-4-ira.weiny@intel.com Link: http://lkml.kernel.org/r/20190317183438.2057-4-ira.weiny@intel.com Signed-off-by: Ira Weiny Reviewed-by: Mike Marshall Cc: Aneesh Kumar K.V Cc: Benjamin Herrenschmidt Cc: Borislav Petkov Cc: Dan Williams Cc: "David S. Miller" Cc: Heiko Carstens Cc: Ingo Molnar Cc: James Hogan Cc: Jason Gunthorpe Cc: John Hubbard Cc: "Kirill A. Shutemov" Cc: Martin Schwidefsky Cc: Michal Hocko Cc: Paul Mackerras Cc: Peter Zijlstra Cc: Ralf Baechle Cc: Rich Felker Cc: Thomas Gleixner Cc: Yoshinori Sato Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- net/ceph/pagevec.c | 2 +- net/rds/info.c | 2 +- net/rds/rdma.c | 3 ++- 3 files changed, 4 insertions(+), 3 deletions(-) (limited to 'net') diff --git a/net/ceph/pagevec.c b/net/ceph/pagevec.c index d3736f5bffec..74cafc0142ea 100644 --- a/net/ceph/pagevec.c +++ b/net/ceph/pagevec.c @@ -27,7 +27,7 @@ struct page **ceph_get_direct_page_vector(const void __user *data, while (got < num_pages) { rc = get_user_pages_fast( (unsigned long)data + ((unsigned long)got * PAGE_SIZE), - num_pages - got, write_page, pages + got); + num_pages - got, write_page ? FOLL_WRITE : 0, pages + got); if (rc < 0) break; BUG_ON(rc == 0); diff --git a/net/rds/info.c b/net/rds/info.c index e367a97a18c8..03f6fd56d237 100644 --- a/net/rds/info.c +++ b/net/rds/info.c @@ -193,7 +193,7 @@ int rds_info_getsockopt(struct socket *sock, int optname, char __user *optval, ret = -ENOMEM; goto out; } - ret = get_user_pages_fast(start, nr_pages, 1, pages); + ret = get_user_pages_fast(start, nr_pages, FOLL_WRITE, pages); if (ret != nr_pages) { if (ret > 0) nr_pages = ret; diff --git a/net/rds/rdma.c b/net/rds/rdma.c index 182ab8430594..b340ed4fc43a 100644 --- a/net/rds/rdma.c +++ b/net/rds/rdma.c @@ -158,7 +158,8 @@ static int rds_pin_pages(unsigned long user_addr, unsigned int nr_pages, { int ret; - ret = get_user_pages_fast(user_addr, nr_pages, write, pages); + ret = get_user_pages_fast(user_addr, nr_pages, write ? FOLL_WRITE : 0, + pages); if (ret >= 0 && ret < nr_pages) { while (ret--) -- cgit