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SubjectRe: [PATCH v2 4/4] staging: kpc2000: kpc_dma: Remove additional goto statements
On Tue, Jun 30, 2020 at 01:22:19PM +0530, Souptick Joarder wrote:
> As 3 goto level referring to same common code, those can be
> accomodated with a single goto level and renameing it to
> unpin_pages. Set the -ERRNO when returning partial mapped
> pages in more appropriate place.
>
> Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
> Cc: John Hubbard <jhubbard@nvidia.com>
> Cc: Bharath Vedartham <linux.bhar@gmail.com>
> Cc: Dan Carpenter <dan.carpenter@oracle.com>
> ---
> drivers/staging/kpc2000/kpc_dma/fileops.c | 24 ++++++++++++------------
> 1 file changed, 12 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/staging/kpc2000/kpc_dma/fileops.c b/drivers/staging/kpc2000/kpc_dma/fileops.c
> index 8cd20ad..d21a4fd 100644
> --- a/drivers/staging/kpc2000/kpc_dma/fileops.c
> +++ b/drivers/staging/kpc2000/kpc_dma/fileops.c
> @@ -35,7 +35,7 @@ static int kpc_dma_transfer(struct dev_private_data *priv,
> unsigned long iov_base, size_t iov_len)
> {
> unsigned int i = 0;
> - int rv = 0;
> + int rv = 0, nr_pages = 0;
> struct kpc_dma_device *ldev;
> struct aio_cb_data *acd;
> DECLARE_COMPLETION_ONSTACK(done);
> @@ -79,22 +79,27 @@ static int kpc_dma_transfer(struct dev_private_data *priv,
> 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) {
> + nr_pages = rv;
> + if (rv > 0)
> + rv = -EFAULT;
> +
> dev_err(&priv->ldev->pldev->dev, "Couldn't pin_user_pages (%d)\n", rv);
> - goto err_get_user_pages;
> + goto unpin_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) {
> dev_err(&priv->ldev->pldev->dev, "Couldn't alloc sg_table (%d)\n", rv);
> - goto err_alloc_sg_table;
> + goto unpin_pages;
> }
>
> // Setup the DMA mapping for all the sg entries
> acd->mapped_entry_count = dma_map_sg(&ldev->pldev->dev, acd->sgt.sgl, acd->sgt.nents, ldev->dir);
> if (acd->mapped_entry_count <= 0) {
> dev_err(&priv->ldev->pldev->dev, "Couldn't dma_map_sg (%d)\n", acd->mapped_entry_count);
> - goto err_dma_map_sg;
> + goto unpin_pages;

This wasn't introduced by your patch but the most recent successful
allocation is sg_alloc_table_from_pages() so this should be goto
free_table:

free_table:
sg_free_table(&acd->sgt);
unpin_pages:
if (nr_pages > 0)
unpin_user_pages(acd->user_pages, nr_pages);

Always just keep track of the most recent allocation and check that the
"goto free_foo" matches what you would expect to release the most
recent thing.

> }
>
> // Calculate how many descriptors are actually needed for this transfer.
> @@ -187,15 +192,10 @@ static int kpc_dma_transfer(struct dev_private_data *priv,
> unlock_engine(ldev);
> dma_unmap_sg(&ldev->pldev->dev, acd->sgt.sgl, acd->sgt.nents, ldev->dir);
> sg_free_table(&acd->sgt);
^^^^^^^^^^^^^^^^^^^^^^^^

> - err_dma_map_sg:
> - err_alloc_sg_table:
> - unpin_user_pages(acd->user_pages, acd->page_count);
>
> - err_get_user_pages:
> - if (rv > 0) {
> - unpin_user_pages(acd->user_pages, rv);
> - rv = -EFAULT;
> - }
> + unpin_pages:
> + if (nr_pages > 0)
> + unpin_user_pages(acd->user_pages, nr_pages);
> kfree(acd->user_pages);
> err_alloc_userpages:
> kfree(acd);

regards,
dan carpenter

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