There have been issues with get_user_pages and filesystem writeback. The issues are better described in [1].
The solution being proposed wants to keep track of gup_pinned pages which will allow to take furthur steps to coordinate between subsystems using gup. put_user_page() simply calls put_page inside for now. But the implementation will change once all call sites of put_page() are converted. [1] https://lwn.net/Articles/753027/ Cc: Matt Sickler <matt.sick...@daktronics.com> Cc: Greg Kroah-Hartman <gre...@linuxfoundation.org> Cc: Jérôme Glisse <jgli...@redhat.com> Cc: Ira Weiny <ira.we...@intel.com> Cc: John Hubbard <jhubb...@nvidia.com> Cc: linux...@kvack.org Cc: de...@driverdev.osuosl.org Reviewed-by: John Hubbard <jhubb...@nvidia.com> Signed-off-by: Bharath Vedartham <linux.b...@gmail.com> --- Changes since v1 - Added John's reviewed-by tag - Moved para talking about testing below the '---' - Moved logic of set_page_diry below dma_unmap_sg as per John's suggestion I currently do not have the driver to test. Could I have some suggestions to test this code? The solution is currently implemented in https://github.com/johnhubbard/linux/tree/gup_dma_core and it would be great if we could apply the patch on top of the repo and run some tests to check if any regressions occur. --- drivers/staging/kpc2000/kpc_dma/fileops.c | 17 ++++++----------- 1 file changed, 6 insertions(+), 11 deletions(-) diff --git a/drivers/staging/kpc2000/kpc_dma/fileops.c b/drivers/staging/kpc2000/kpc_dma/fileops.c index 48ca88b..3d1a00a 100644 --- a/drivers/staging/kpc2000/kpc_dma/fileops.c +++ b/drivers/staging/kpc2000/kpc_dma/fileops.c @@ -190,9 +190,7 @@ static int kpc_dma_transfer(struct dev_private_data *priv, 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: @@ -211,16 +209,13 @@ void transfer_complete_cb(struct aio_cb_data *acd, size_t xfr_count, u32 flags) BUG_ON(acd->ldev == NULL); BUG_ON(acd->ldev->pldev == NULL); - for (i = 0 ; i < acd->page_count ; i++) { - if (!PageReserved(acd->user_pages[i])) { - set_page_dirty(acd->user_pages[i]); - } - } - dma_unmap_sg(&acd->ldev->pldev->dev, acd->sgt.sgl, acd->sgt.nents, acd->ldev->dir); - for (i = 0 ; i < acd->page_count ; i++) { - put_page(acd->user_pages[i]); + for (i = 0; i < acd->page_count; i++) { + if (!PageReserved(acd->user_pages[i])) + put_user_pages_dirty(&acd->user_pages[i], 1); + else + put_user_page(acd->user_pages[i]); } sg_free_table(&acd->sgt); -- 2.7.4 _______________________________________________ devel mailing list de...@linuxdriverproject.org http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
