On Mon, Jul 15, 2019 at 12:26:54PM +0530, Bharath Vedartham wrote: > On Sun, Jul 14, 2019 at 04:33:42PM -0700, John Hubbard wrote: > > On 7/14/19 12:08 PM, Bharath Vedartham wrote: > > > This patch converts all call sites of get_user_pages > > > to use put_user_page*() instead of put_page*() functions to > > > release reference to gup pinned pages. > Hi John, > > Hi Bharath, > > > > Thanks for jumping in to help, and welcome to the party! > > > > You've caught everyone in the middle of a merge window, btw. As a > > result, I'm busy rebasing and reworking the get_user_pages call sites, > > and gup tracking, in the wake of some semi-traumatic changes to bio > > and gup and such. I plan to re-post right after 5.3-rc1 shows up, from > > here: > > > > https://github.com/johnhubbard/linux/commits/gup_dma_core > > > > ...which you'll find already covers the changes you've posted, except for: > > > > drivers/misc/sgi-gru/grufault.c > > drivers/staging/kpc2000/kpc_dma/fileops.c > > > > ...and this one, which is undergoing to larger local changes, due to > > bvec, so let's leave it out of the choices: > > > > fs/io_uring.c > > > > Therefore, until -rc1, if you'd like to help, I'd recommend one or more > > of the following ideas: > > > > 1. Pull down https://github.com/johnhubbard/linux/commits/gup_dma_core > > and find missing conversions: look for any additional missing > > get_user_pages/put_page conversions. You've already found a couple missing > > ones. I haven't re-run a search in a long time, so there's probably even more. > > a) And find more, after I rebase to 5.3-rc1: people probably are adding > > get_user_pages() calls as we speak. :) > Shouldn't this be documented then? I don't see any docs for using > put_user_page*() in v5.2.1 in the memory management API section? > > 2. Patches: Focus on just one subsystem at a time, and perfect the patch for > > it. For example, I think this the staging driver would be perfect to start with: > > > > drivers/staging/kpc2000/kpc_dma/fileops.c > > > > a) verify that you've really, corrected converted the whole > > driver. (Hint: I think you might be overlooking a put_page call.) > Yup. I did see that! Will fix it! > > b) Attempt to test it if you can (I'm being hypocritical in > > the extreme here, but one of my problems is that testing > > has been light, so any help is very valuable). qemu...? > > OTOH, maybe even qemu cannot easily test a kpc2000, but > > perhaps `git blame` and talking to the authors would help > > figure out a way to validate the changes. > Great! I ll do that, I ll mail the patch authors and ask them for help > in testing. > > Thinking about whether you can run a test that would prove or > > disprove my claim in (a), above, could be useful in coming up > > with tests to run. > > > In other words, a few very high quality conversions (even just one) that > > we can really put our faith in, is what I value most here. Tested patches > > are awesome. > I understand that! > > 3. Once I re-post, turn on the new CONFIG_DEBUG_GET_USER_PAGES_REFERENCES > > and run things such as xfstest/fstest. (Again, doing so would be going > > further than I have yet--very helpful). Help clarify what conversions have > > actually been tested and work, and which ones remain unvalidated. > > Other: Please note that this: > Yup will do that. > > https://github.com/johnhubbard/linux/commits/gup_dma_core > > > > a) gets rebased often, and > > > > b) has a bunch of commits (iov_iter and related) that conflict > > with the latest linux.git, > > > > c) has some bugs in the bio area, that I'm fixing, so I don't trust > > that's it's safely runnable, for a few more days. > I assume your repo contains only work related to fixing gup issues and > not the main repo for gup development? i.e where gup changes are merged? We have been using Andrews tree for merging. > Also are release_pages and put_user_pages interchangable? Conceptually yes. But release_pages is more efficient. There was some discussion around this starting here: https://lore.kernel.org/lkml/20190523172852.GA27175@xxxxxxxxxxxxxxxxxxxxxxxxx/ And a resulting bug fix. https://lkml.org/lkml/2019/6/21/95 Ira > > One note below, for the future: > > > > > > > > This is a bunch of trivial conversions which is a part of an effort > > > by John Hubbard to solve issues with gup pinned pages and > > > filesystem writeback. > > > > > > The issue is more clearly described in John Hubbard's patch[1] where > > > put_user_page*() functions are introduced. > > > > > > Currently put_user_page*() simply does put_page but future implementations > > > look to change that once treewide change of put_page callsites to > > > put_user_page*() is finished. > > > > > > The lwn article describing the issue with gup pinned pages and filesystem > > > writeback [2]. > > > > > > This patch has been tested by building and booting the kernel as I don't > > > have the required hardware to test the device drivers. > > > > > > I did not modify gpu/drm drivers which use release_pages instead of > > > put_page() to release reference of gup pinned pages as I am not clear > > > whether release_pages and put_page are interchangable. > > > > > > [1] https://lkml.org/lkml/2019/3/26/1396 > > > > When referring to patches in a commit description, please use the > > commit hash, not an external link. See Submitting Patches [1] for details. > > > > Also, once you figure out the right maintainers and other involved people, > > putting Cc: in the commit description is common practice, too. > > > > [1] https://www.kernel.org/doc/html/latest/process/submitting-patches.html > Will work on that! Thanks! > > thanks, > > -- > > John Hubbard > > NVIDIA > > > > > > > > [2] https://lwn.net/Articles/784574/ > > > > > > Signed-off-by: Bharath Vedartham <linux.bhar@xxxxxxxxx> > > > --- > > > drivers/media/v4l2-core/videobuf-dma-sg.c | 3 +-- > > > drivers/misc/sgi-gru/grufault.c | 2 +- > > > drivers/staging/kpc2000/kpc_dma/fileops.c | 4 +--- > > > drivers/vfio/vfio_iommu_type1.c | 2 +- > > > fs/io_uring.c | 7 +++---- > > > mm/gup_benchmark.c | 6 +----- > > > net/xdp/xdp_umem.c | 7 +------ > > > 7 files changed, 9 insertions(+), 22 deletions(-) > > > > > > diff --git a/drivers/media/v4l2-core/videobuf-dma-sg.c b/drivers/media/v4l2-core/videobuf-dma-sg.c > > > index 66a6c6c..d6eeb43 100644 > > > --- a/drivers/media/v4l2-core/videobuf-dma-sg.c > > > +++ b/drivers/media/v4l2-core/videobuf-dma-sg.c > > > @@ -349,8 +349,7 @@ int videobuf_dma_free(struct videobuf_dmabuf *dma) > > > BUG_ON(dma->sglen); > > > > > > if (dma->pages) { > > > - for (i = 0; i < dma->nr_pages; i++) > > > - put_page(dma->pages[i]); > > > + put_user_pages(dma->pages, dma->nr_pages); > > > kfree(dma->pages); > > > dma->pages = NULL; > > > } > > > diff --git a/drivers/misc/sgi-gru/grufault.c b/drivers/misc/sgi-gru/grufault.c > > > index 4b713a8..61b3447 100644 > > > --- a/drivers/misc/sgi-gru/grufault.c > > > +++ b/drivers/misc/sgi-gru/grufault.c > > > @@ -188,7 +188,7 @@ static int non_atomic_pte_lookup(struct vm_area_struct *vma, > > > if (get_user_pages(vaddr, 1, write ? FOLL_WRITE : 0, &page, NULL) <= 0) > > > return -EFAULT; > > > *paddr = page_to_phys(page); > > > - put_page(page); > > > + put_user_page(page); > > > return 0; > > > } > > > > > > diff --git a/drivers/staging/kpc2000/kpc_dma/fileops.c b/drivers/staging/kpc2000/kpc_dma/fileops.c > > > index 6166587..26dceed 100644 > > > --- a/drivers/staging/kpc2000/kpc_dma/fileops.c > > > +++ b/drivers/staging/kpc2000/kpc_dma/fileops.c > > > @@ -198,9 +198,7 @@ int kpc_dma_transfer(struct dev_private_data *priv, struct kiocb *kcb, unsigned > > > sg_free_table(&acd->sgt); > > > err_dma_map_sg: > > > err_alloc_sg_table: > > > - for (i = 0 ; i < acd->page_count ; i++){ > > > - put_page(acd->user_pages[i]); > > > - } > > > + put_user_pages(acd->user_pages, acd->page_count); > > > err_get_user_pages: > > > kfree(acd->user_pages); > > > err_alloc_userpages: > > > diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c > > > index add34ad..c491524 100644 > > > --- a/drivers/vfio/vfio_iommu_type1.c > > > +++ b/drivers/vfio/vfio_iommu_type1.c > > > @@ -369,7 +369,7 @@ static int vaddr_get_pfn(struct mm_struct *mm, unsigned long vaddr, > > > */ > > > if (ret > 0 && vma_is_fsdax(vmas[0])) { > > > ret = -EOPNOTSUPP; > > > - put_page(page[0]); > > > + put_user_page(page[0]); > > > } > > > } > > > up_read(&mm->mmap_sem); > > > diff --git a/fs/io_uring.c b/fs/io_uring.c > > > index 4ef62a4..b4a4549 100644 > > > --- a/fs/io_uring.c > > > +++ b/fs/io_uring.c > > > @@ -2694,10 +2694,9 @@ static int io_sqe_buffer_register(struct io_ring_ctx *ctx, void __user *arg, > > > * if we did partial map, or found file backed vmas, > > > * release any pages we did get > > > */ > > > - if (pret > 0) { > > > - for (j = 0; j < pret; j++) > > > - put_page(pages[j]); > > > - } > > > + if (pret > 0) > > > + put_user_pages(pages, pret); > > > + > > > if (ctx->account_mem) > > > io_unaccount_mem(ctx->user, nr_pages); > > > kvfree(imu->bvec); > > > diff --git a/mm/gup_benchmark.c b/mm/gup_benchmark.c > > > index 7dd602d..15fc7a2 100644 > > > --- a/mm/gup_benchmark.c > > > +++ b/mm/gup_benchmark.c > > > @@ -76,11 +76,7 @@ static int __gup_benchmark_ioctl(unsigned int cmd, > > > gup->size = addr - gup->addr; > > > > > > start_time = ktime_get(); > > > - for (i = 0; i < nr_pages; i++) { > > > - if (!pages[i]) > > > - break; > > > - put_page(pages[i]); > > > - } > > > + put_user_pages(pages, nr_pages); > > > end_time = ktime_get(); > > > gup->put_delta_usec = ktime_us_delta(end_time, start_time); > > > > > > diff --git a/net/xdp/xdp_umem.c b/net/xdp/xdp_umem.c > > > index 9c6de4f..6103e19 100644 > > > --- a/net/xdp/xdp_umem.c > > > +++ b/net/xdp/xdp_umem.c > > > @@ -173,12 +173,7 @@ static void xdp_umem_unpin_pages(struct xdp_umem *umem) > > > { > > > unsigned int i; > > > > > > - for (i = 0; i < umem->npgs; i++) { > > > - struct page *page = umem->pgs[i]; > > > - > > > - set_page_dirty_lock(page); > > > - put_page(page); > > > - } > > > + put_user_pages_dirty_lock(umem->pgs, umem->npgs); > > > > > > kfree(umem->pgs); > > > umem->pgs = NULL; > > >
