On Mon, Jun 1, 2020 at 7:15 AM John Hubbard <jhubbard@xxxxxxxxxx> wrote: > > On 2020-05-31 10:51, Souptick Joarder wrote: > > In 2019, we introduced pin_user_pages*() and now we are converting > > get_user_pages*() to the new API as appropriate. [1] & [2] could > > be referred for more information. > > > > When pin_user_pages() returns numbers of partially mapped pages, > > those pages were not unpinned as part of error handling. Fixed > > it as part of this patch. > > > > Hi Souptick, > > btw, Bharath (+cc) attempted to do the "put" side of this, last year. > That got as far as a v4 patch [1], and then I asked him to let me put > it into my tree. But then it didn't directly apply anymore after the > whole design moved to pin+unpin, and so here we are now. > > > If Bharath is still doing kernel work, you might offer him a Co-Developed-by: > tag (see https://www.kernel.org/doc/html/v4.17/process/submitting-patches.html). Sure, will add him as *Co-Developed-by* > > Anyway, I'd recommend splitting the bug fix(es) into it at least one > separate patch. That's a "best practice", and I don't see any reason > not to do it here, even though the bugs are not huge. > > Also I think there may be more than one bug to fix, because I just > noticed that the pre-existing code is doing set_page_dirty(), when > it should be doing set_page_dirty_lock(). See below. > > > > [1] Documentation/core-api/pin_user_pages.rst > > > > [2] "Explicit pinning of user-space pages": > > https://lwn.net/Articles/807108/ > > > > Signed-off-by: Souptick Joarder <jrdr.linux@xxxxxxxxx> > > Cc: John Hubbard <jhubbard@xxxxxxxxxx> > > --- > > Hi, > > > > I'm compile tested this, but unable to run-time test, so any testing > > help is much appriciated. > > > > drivers/staging/kpc2000/kpc_dma/fileops.c | 15 ++++++++------- > > 1 file changed, 8 insertions(+), 7 deletions(-) > > > > diff --git a/drivers/staging/kpc2000/kpc_dma/fileops.c b/drivers/staging/kpc2000/kpc_dma/fileops.c > > index 8975346..29bab13 100644 > > --- a/drivers/staging/kpc2000/kpc_dma/fileops.c > > +++ b/drivers/staging/kpc2000/kpc_dma/fileops.c > > @@ -48,6 +48,7 @@ static int kpc_dma_transfer(struct dev_private_data *priv, > > u64 card_addr; > > u64 dma_addr; > > u64 user_ctl; > > + int nr_pages = 0; > > Probably best to correct the "rv" type as well: it should be an int, rather > than a long. Noted. > > > > > ldev = priv->ldev; > > > > @@ -76,13 +77,15 @@ static int kpc_dma_transfer(struct dev_private_data *priv, > > > > // Lock the user buffer pages in memory, and hold on to the page pointers (for the sglist) > > mmap_read_lock(current->mm); /* get memory map semaphore */ > > - rv = get_user_pages(iov_base, acd->page_count, FOLL_TOUCH | FOLL_WRITE | FOLL_GET, acd->user_pages, NULL); > > + rv = pin_user_pages(iov_base, acd->page_count, FOLL_TOUCH | FOLL_WRITE, acd->user_pages, NULL); > > mmap_read_unlock(current->mm); /* release the semaphore */ > > if (rv != acd->page_count) { > > - dev_err(&priv->ldev->pldev->dev, "Couldn't get_user_pages (%ld)\n", rv); > > + dev_err(&priv->ldev->pldev->dev, "Couldn't pin_user_pages (%ld)\n", rv); > > + nr_pages = rv; > > goto err_get_user_pages; > > } > > > > + nr_pages = acd->page_count; > > // Allocate and setup the sg_table (scatterlist entries) > > rv = sg_alloc_table_from_pages(&acd->sgt, acd->user_pages, acd->page_count, iov_base & (PAGE_SIZE - 1), iov_len, GFP_KERNEL); > > if (rv) { > > @@ -189,10 +192,9 @@ static int kpc_dma_transfer(struct dev_private_data *priv, > > sg_free_table(&acd->sgt); > > err_dma_map_sg: > > err_alloc_sg_table: > > So now we end up with two unnecessary labels. Probably best to delete two of these > three and name the remaining one appropriately: Hmm, I thought about it. But later decided to wait for review comments on the same in v1. I will remove it now. > > err_dma_map_sg: > err_alloc_sg_table: > err_get_user_pages: > > > - for (i = 0 ; i < acd->page_count ; i++) > > - put_page(acd->user_pages[i]); > > - > > err_get_user_pages: > > + if (nr_pages > 0) > > + unpin_user_pages(acd->user_pages, nr_pages); > > kfree(acd->user_pages); > > err_alloc_userpages: > > kfree(acd); > > @@ -217,8 +219,7 @@ void transfer_complete_cb(struct aio_cb_data *acd, size_t xfr_count, u32 flags) > > > > There is code up here (not shown in this diff), that does a set_page_dirty(). > First of all, that should be set_page_dirty_lock(), and second, maybe (or maybe not) > it can all be done after the dma_unmap_sg(), at the same time as the unpin, via > unpin_user_pages_dirty_lock(). In fact, it's misleading at best to leave those > pages mapped, because there is an interval in there after set_page_dirty() and > before put_page(), in which the device could be running and setting pages dirty. > (Remember that writeback attempts can be happening concurrently with all of this, > and writeback is deeply involved with page dirtiness.) > > I remember Bharath wrestled with this in an earlier conversion attempt (back when > we were only converting the "put_page" side of things), let me see if I can dig up > that email thread for some guidance...OK, in [1] it appears that everyone > finally settled on keeping the PageReserved check, but OK to move everything below > the dma_unmap_sg() call. > > [1] https://lore.kernel.org/r/20190720173214.GA4250@bharath12345-Inspiron-5559 Well, I need to rework on this based on the above feedback and suggestions. Will post the new series. > > > > 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]); > > + unpin_user_pages(acd->user_pages, acd->page_count); > > > > sg_free_table(&acd->sgt); > > > > > > thanks, > -- > John Hubbard > NVIDIA _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
