On 7/15/19 12:52 PM, Bharath Vedartham wrote: > 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. > > I currently do not have the driver to test. Could I have some suggestions to test this code? The solution is currently implemented in [2] and > it would be great if we could apply the patch on top of [2] and run some tests to check if any regressions occur. Hi Bharath, Process point: the above paragraph, and other meta-questions (about the patch, rather than part of the patch) should be placed either after the "---", or in a cover letter (git-send-email --cover-letter). That way, the patch itself is in a commit-able state. One more below: > > [1] https://lwn.net/Articles/753027/ > [2] https://github.com/johnhubbard/linux/tree/gup_dma_core > > Cc: Matt Sickler <Matt.Sickler@xxxxxxxxxxxxxx> > Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > Cc: Jérôme Glisse <jglisse@xxxxxxxxxx> > Cc: Ira Weiny <ira.weiny@xxxxxxxxx> > Cc: John Hubbard <jhubbard@xxxxxxxxxx> > Cc: linux-mm@xxxxxxxxx > Cc: devel@xxxxxxxxxxxxxxxxxxxx > > Signed-off-by: Bharath Vedartham <linux.bhar@xxxxxxxxx> > --- > drivers/staging/kpc2000/kpc_dma/fileops.c | 8 ++------ > 1 file changed, 2 insertions(+), 6 deletions(-) > > diff --git a/drivers/staging/kpc2000/kpc_dma/fileops.c b/drivers/staging/kpc2000/kpc_dma/fileops.c > index 6166587..82c70e6 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: > @@ -229,9 +227,7 @@ void transfer_complete_cb(struct aio_cb_data *acd, size_t xfr_count, u32 flags) > > 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]); > - } > + put_user_pages(acd->user_pages, acd->page_count); > > sg_free_table(&acd->sgt); > > Because this is a common pattern, and because the code here doesn't likely need to set page dirty before the dma_unmap_sg call, I think the following would be better (it's untested), instead of the above diff hunk: diff --git a/drivers/staging/kpc2000/kpc_dma/fileops.c b/drivers/staging/kpc2000/kpc_dma/fileops.c index 48ca88bc6b0b..d486f9866449 100644 --- a/drivers/staging/kpc2000/kpc_dma/fileops.c +++ b/drivers/staging/kpc2000/kpc_dma/fileops.c @@ -211,16 +211,13 @@ 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]); + 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); Assuming that you make those two changes, you can add: Reviewed-by: John Hubbard <jhubbard@xxxxxxxxxx> thanks, -- John Hubbard NVIDIA
